The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of competing designs from larger companies such as Motorola and Intel. It was nevertheless fully comparable with them and, along with the Zilog Z80, sparked a series of computer projects that would eventually result in the home computer revolution of the 1980s. The 6502 design was originally second-sourced by Rockwell and Synertek and later licensed to a number of companies. Soon after the 6502's introduction, MOS Technology was bought outright by Commodore International, who continued to sell the chip to other manufacturers.

History and use

Origins at Motorola

The 6502 was designed primarily by the same engineering team that had designed the Motorola 6800. One of the designers, Chuck Peddle, traveled around with the 6800 to introduce it to potential industrial customers. At the time it was targeted at the embedded market, and although their presentations sparked interest, the price, at about , was simply too high to be widely used. When he asked what sort of price would make the product useful, they settled on . Peddle returned to Motorola and proposed producing a low-cost product to attack this market, but found that management was uninterested; the 6800 was generating nice profits, there seemed to be no reason to change their sales efforts.

Undaunted, Peddle started working on such a design on his own. The new design was similar to the 6800 in that it also used a small number of processor registers with a single accumulator. The new design fixed one of the 6800's greatest problems, and allowed the accumulator and index registers to be used together as inputs and offsets. Other additions included the ability to perform binary coded decimal arithmetic and on-chip clock generation; only a single external clock signal was needed, and the new CPU could itself supply clock signals to other chips in a system, eliminating the need for a number of external components.

As the effort continued, the design team grew increasingly unhappy with management's lack of support. At the same time, management grew increasingly upset with the team spending time on a project they didn't support. Eventually Peddle was sent an official memo from management telling him to stop working on the low-cost design. In response, much of the original 6800 design team resigned ''en masse'' and went looking for a company that would be interested in building their new design.

Moving to MOS

The team was soon in negotiations with MOS Technology, at that time a small fab who produced chips for 3rd parties with limited internal design capability. The company had originally been set up by Allen-Bradley as a second-source for Texas Instruments calculator chips, but had since branched out to produce runs for a number of different companies. One of their recent products at the time was a single-chip implementation of the popular Pong video game. The existing MOS engineers were not pleased to find an entire new team parachuted into their company. They were even more upset when they learned that the team would be cut in on part of any profits the new design generated.

At MOS, the Motorola team quickly designed the 6501, a new processor that was designed to be pin-compatible with the 6800. This allowed it to be plugged into motherboards designed for the Motorola processor, like the the MEK6800D2, although its instruction set was different. Motorola sued immediately, and MOS agreed to stop producing the 6501 and went back to the drawing board. The result was the "lawsuit-compatible" 6502, which was by design unusable in a 6800 motherboard but otherwise identical to the 6501. Motorola had no objection to this version.

However, this left MOS with the problem of getting developers to try their processor, so Peddle designed the MDT-650 (for "microcomputer development terminal") single-board computer. Another group inside the company designed the KIM-1, which was sold semi-complete and could be turned into a usable system with the addition of a 3rd party computer terminal and compact cassette drive. Much to their surprise, the KIM-1 sold well to hobbyists and tinkerers, as well as to the engineers it was intended for. The related Rockwell AIM 65 control/training/development system also did well. The software in the AIM 65 was based on that in the MDT. Another roughly similar product was the Synertek SYM-1.

Introducing the 6502

The 6502 was introduced at ($}} today) at the Wescon show in September 1975. The company had an off-floor suite with a big jar full of the chips. However with this early run they only had a handful of working ones. To give the appearance of larger quantities, the bottom of the jar was stuffed with defective chips, and only the ones at the top of the jar worked. At the same show the 6800 and Intel 8080 were selling for . At first many people thought the new chip's price was a hoax or a mistake, but while the show was still ongoing both Motorola and Intel had dropped their chips to . These price reductions legitimized the 6502, which started selling by the hundreds.

One of the first "public" uses for the design was the Apple I computer, introduced in 1976. The 6502 was next used in the Atari 2600, Commodore PET and the Apple II, all released in 1977. It was later used in the Atari home computers, the BBC Micro family, the Commodore VIC-20 and a large number of other designs both for home computers and business, such as Ohio Scientific and Oric. The 6510, a direct successor of the 6502 with a digital I/O port and a tri-state address bus, was the CPU utilized in the Commodore 64 home computer. (Commodore's disk drive, the 1541, had a processor of its own—it too was a 6502.)

Another important use of the 6500 family was in video games. The first to make use was the Atari 2600 video game console. The 2600 used an offshoot of the 6502 called the 6507, which had fewer pins and, as a result, could address only 8 KB of memory. Millions of the Atari consoles would be sold, each with a MOS processor. Another significant use was by the Nintendo Famicom, a Japanese video game console. Its international equivalent, the Nintendo Entertainment System, also used the processor. The 6502 used in the NES was a second source version by Ricoh, a partial system-on-a-chip, that lacked the binary-coded decimal mode but added 22 memory-mapped registers (and on-die hardware) for sound generation, joypad reading, and sprite list DMA. Called 2A03 in NTSC consoles and 2A07 in PAL consoles (the difference being the memory divider ratio and a lookup table for audio sample rates), this processor was produced exclusively for Nintendo.

Technical description

The 6502 is an 8-bit processor with a 16-bit address bus. The internal logic runs at the same speed as the external clock rate, but despite the slow clock speeds (typically in the neighborhood of 1 to 2 MHz), the 6502's performance was actually competitive with other CPUs using significantly faster clocks. This is partly due to a simplistic state machine implemented by combinatorial (clockless) logic to a greater extent than in many other designs; the two phase clock (supplying two synchronizations per cycle) can thereby control the whole ''machine''-cycle directly. Like most simple CPUs of the era, the dynamic NMOS 6502 chip was not sequenced by a microcode ROM but used a PLA (which occupied about 15% of the chip area) for instruction decoding and sequencing. Like most eight-bit microprocessors, the chip does some limited overlapping of fetching and execution.

The low clock frequency moderated the speed requirement of memory and peripherals attached to the CPU, as only about 50% of the clock cycle was available for memory access (due to the asynchronous design, this percentage varied strongly among chip versions). This was critical at a time when affordable memory had access times in the range 450-250ns. The original NMOS 6502 was minimalistically engineered and efficiently manufactured and therefore cheap—an important factor in getting design wins in the very price-sensitive game console and home computer markets.

Like its precursor, the Motorola 6800, the 6502 has very few registers. At the time the processor was designed, the number of transistors that could be economically put on a chip was very constrained (around a few thousand), so it made sense to rely on RAM instead of allocating expensive NMOS chip area for CPU registers.

The 6502's registers included one 8-bit accumulator register (A), two 8-bit index registers (X and Y), an 8-bit processor status register (P), an 8-bit stack pointer (S), and a 16-bit program counter (PC). The stack's address space was hardwired to memory page $01, i.e. the address range $0100–$01FF (256–511). Software access to the stack was done via four implied addressing mode instructions whose functions were to push or pop (pull) the accumulator or the processor status register. The same stack was also used for subroutine calls via the JSR (Jump to Subroutine) and RTS (Return from Subroutine) instructions, and for interrupt handling.

The chip used the index and stack registers effectively with several addressing modes, including a fast "direct page" or "zero page" mode, similar to that found on the PDP-8, that accessed memory locations from address 0 to 255 with a single 8-bit address (saving the cycle normally required to fetch the high-order byte of the address)—code for the 6502 used the zero page much as code for other processors would have used registers. On some 6502-based microcomputers with an operating system, the OS would use most of zero page, leaving only a handful of locations for the user.

Addressing modes also included ''implied'' (1 byte instructions); ''absolute'' (3 bytes); ''indexed absolute'' (3 bytes); ''indexed zero-page'' (2 bytes); ''relative'' (2 bytes); ''accumulator'' (1); ''indirect,x'' and ''indirect,y'' (2); and ''immediate'' (2). Absolute mode was a general-purpose mode. Branch instructions used a signed 8-bit offset relative to the instruction after the branch; the numerical range -128..127 therefore translates to 128 bytes backward and 127 bytes forward from the instruction following the branch (which is 126 bytes backward and 129 bytes forward from the start of the branch instruction). Accumulator mode used the accumulator as an effective address, and did not need any operand data. Immediate mode used an 8-bit literal operand.

The indirect modes were useful for array processing and other looping. With the 5/6 cycle "(indirect),y" mode, the 8-bit Y register was added to a 16-bit base address in zero page which was located by a single byte following the opcode. The Y register was therefore an ''index''-register in the sense that it was used to hold an actual ''index'' (as opposed to the X register in the 6800 where a base address was directly stored and to which an immediate offset could be added). Incrementing the index register to walk the array byte-wise took only two additional cycles. With the less frequently used "(indirect,x)" mode the effective address for the operation was found at the zero page address formed by adding the second byte of the instruction to the contents of the X register. Using the indexed modes, the zero page effectively acted as a set of 128 additional (though very slow) address registers.

The 6502 is capable of performing addition and subtraction in binary or binary coded decimal. Placing the CPU into BCD mode with the SED instruction results in decimal arithmetic, in which $99 + $01 would result in $00 and the carry flag being set. In binary mode (CLD), the same operation would result in $9A and the carry flag being cleared. Other than Atari BASIC, BCD mode was seldom used in home computer applications.

A Byte magazine article once referred to the 6502 as "the original RISC processor," due to its efficient, simplistic, and nearly orthogonal instruction set (most instructions work with most addressing modes), as well as its 256 zero-page "registers". The 6502 is technically not a RISC design however, as arithmetic operations can read any memory cell (not only zero-page), and some instructions (inc, rol etc.) even modify memory contrary to the basic load/store philosophy of RISC. Furthermore, orthogonality is equally often associated with "CISC". However the 6502 performed reasonably well compared to other contemporary processors such as the Z80, which used a much faster clock rate, and the 6502 has been credited as being inspirational to RISC processors such as the ARM. However the inspiration from the 6502 was related to the simple implementation, rather than the architecture, which is very different to that of the ARM. Also Sophie Wilson, who designed the instruction set for the ARM, has stated that the 6502 has little in common with the ARM processor.

See the Hello world! article for a simple but characteristic example of 6502 assembly language.

Detailed behavior

The processor's non-maskable interrupt (NMI) input is edge sensitive, which means that if the source of an NMI holds the line low, further NMIs after the first are effectively disabled.

The simultaneous assertion of the NMI (non-maskable) and IRQ (maskable) hardware interrupt lines causes IRQ to be ignored. However, if the IRQ line remains asserted after the servicing of the NMI, the processor will immediately respond to IRQ, as IRQ is level sensitive. Thus a sort of built-in interrupt priority was established in the 6502 design.

The "Break" flag of the processor is very different from the other flag bits. It has no flag setting, resetting, and testing instructions of its own, and is not handled by the PHP and PLP instructions either. It exists only on the stack, where BRK and PHP always write a 1, while IRQ and NMI always write a 0.

The "SO" input pin, when asserted, would set the processor's overflow status bit (deasserting it does not clear the overflow bit, however). This can be used by a high-speed polling device driver, which can poll the hardware once in only three cycles by using a Branch-on-oVerflow-Clear (BVC) instruction that branches to itself; for example the Commodore 1541 and other Commodore floppy disk drives use it to detect as quickly as possible whether the serializer is ready to accept or provide another byte of disk data, as a normal test-and-branch loop takes seven cycles which is too slow in that particular application. Obviously great care must be used in the device driver and the associated system design, as spurious assertion of the overflow bit could ruin arithmetic processing.

Variations and Derivatives

There were several variants of the NMOS 6502 produced:

The MOS Technology 6507 had reduced memory addressing capability and no interrupts.

The MOS Technology 6510 has a built-in 6-bit programmable input/output port.

The WDC 65C02 was made in CMOS, had more opcodes, and fixed some outstanding bugs.

The Ricoh 2A03 was a 6502 variant lacking the BCD Mode, used in the Nintendo Entertainment System.

6512

The MOS Technology 6512 was used in the BBC Micro B+64, and relied on an external clock. (The 6502 used an internal clock generator to generate the Phase 1 and Phase 2 clocks.) This was used to advantage in some designs where the clocks could be run asymmetrically, increasing overall CPU performance.

16-bit derivatives

The Western Design Center designed and produced the 65C816 processor, a 16-bit successor to the 65C02, as well as a hybrid offshoot called the 65C802 which was a 65C816 core with a 64 KB address space in a 65(C)02 pin-compatible package—it could be plugged into a 6502 board and would function as a 65C02, or it could be configured via software to expose its 16 bit accumulator and index registers. Few 65C802 parts were sold, and the chip is no longer produced.

The 65C816 was the core of the widely popular Super Nintendo Entertainment System, and the Apple IIGS. The 65C816 is still widely used, both as a discrete processor and as the core of a microcontroller.

Mitsubishi (now Renesas Technology) made a line of 16-bit microcontrollers with an architecture very similar to the 65816, though it was not 100% compatible.

Synertek published a data sheet and application notes on the SY6516, a 16-bit derivative of the 6502, but the part was never introduced.

Bugs and quirks

The earliest revisions of the 6502, such as those shipped with some KIM-1 computers, had a severe bug in the ROR (rotate right memory or accumulator) instruction. The operation of ROR in these chips is effectively an ASL instruction that does not update the carry status bit. MOS left the instruction out of chip documentation entirely because of the defect, promising that ROR would appear on 6502 chips starting in 1976. The vast majority of 6502 chips in existence today do not exhibit this bug.

The original 6502 and its NMOS derivatives are noted for having a variety of undocumented instructions, which vary from one chip manufacturer to the next. The 6502's instruction decoding is implemented in a hardwired logic array (similar to a programmable logic array) which is only defined for 151 of the 256 available opcodes. The remaining 105 trigger strange and hard-to-predict actions (e.g., immediately crashing the processor, performing several valid instructions at once, or simply doing nothing at all). Eastern House Software developed the "Trap65", a device that plugged between the processor and its socket to convert (trap) unimplemented opcodes into BRK (software interrupt) instructions. Some programmers utilized this feature to extend the 6502's instruction set by providing functionality for the unimplemented opcodes with specially written software intercepted at the BRK instruction's 0xFFFE vector. All of the undefined opcodes have been replaced by NOP instructions in the 65C02 CMOS version, although with varying byte sizes and execution times. In the 65C816, all 256 opcodes perform defined operations.

The 6502's memory indirect jump instruction, JMP (

), is partially broken. If

is hex xxFF (i.e., any word ending in FF), the processor will not jump to the address stored in xxFF and xxFF+1 as expected, but rather the one defined by xxFF and xx00. This defect continued through the entire NMOS line, but was corrected in the CMOS derivatives.

The NMOS 6502's indexed addressing across page boundaries will do an extra read of invalid address. This can cause issues by accessing hardware that acts on a read (e.g., clearing timer or IRQ flags, sending an I/O handshake, etc.). This defect continued through the entire NMOS line, but was fixed in the CMOS derivatives, in which the processor does an extra read of the last instruction byte.

The 6502's read/modify/write instructions perform one read and two write cycles. This characteristic may cause issues by twice accessing hardware that acts on a write. This anomaly continued through the entire NMOS line, but was fixed in the CMOS derivatives, in which the processor will do two reads and one write cycle. Good programming practice will generally avoid executing read/modify/write instructions on hardware registers.

The N (result negative), V (sign bit overflow) and Z (result zero) status flags are not valid when performing arithmetic operations while the processor is in BCD mode, as these flags reflect the binary, not BCD, result. This limitation was removed in the CMOS derivatives. Therefore, this feature may be used to cleanly distinguish CMOS from NMOS CPU versions without using any illegal opcodes.

If the processor happens to be in BCD mode when a hardware interrupt occurs it will not revert to binary mode. This quirk could result in hard-to-solve bugs in the interrupt service routine if it fails to clear BCD mode before performing any arithmetic operations. For example, the Commodore 64's kernel did not correctly handle this processor characteristic, requiring that IRQs be disabled or revectored during BCD math operations. This issue was addressed in the CMOS derivatives as well.

The 6502 instruction set includes BRK (opcode $00), which is technically a software interrupt (similar in spirit to the SWI mnemonic of the 6800 and ARM processors). BRK is most often used to interrupt program execution and start a machine code monitor for testing and debugging during software development. It could also be used to route program execution using a simple jump table (analogous to the manner in which the 8088 and derivatives handle software interrupts by number). Unfortunately, if a hardware interrupt occurs at the same time the processor is fetching a BRK instruction, the NMOS version of the processor will fail to execute BRK and instead proceed as if only a hardware interrupt had occurred. This fault was corrected in the CMOS implementation of the processor.

When executing JSR (jump to subroutine) and RTS (return from subroutine) instructions, the return address pushed to the stack by JSR is that of the last byte of the JSR operand (that is, the most significant byte of the subroutine address), rather than the address of the following instruction. This is because the actual copy (from program counter to stack and then vice-versa) takes place before the automatic increment of the program counter that occurs at the end of every instruction. This characteristic would go unnoticed unless you pulled the return address to pick up parameters in the code stream (a common 6502 programming idiom). It remains a characteristic of 6502 derivatives to this day.

Acceleration

Many users of 1 MHz 6502-based systems soon wished their computers could go faster. As the 6502 is externally-clocked, upgrading the speed involved more than dropping a faster chip into the processor socket; many other components would also need to be modified. To meet user demand, a number of companies sold hardware to speed up those systems. These "accelerators" included a modicum of high-speed RAM and glue circuitry used to synchronize the faster processor with the computer's original RAM and its peripherals. For example, the Apple II floppy disk relied on software accessing the controller's I/O registers with critical timing; Apple II accelerators were therefore designed to fall back to 1 MHz during disk access. The first accelerators were circuit boards; some later accelerators (such as the Zip Chip) miniaturized the processor and support circuits to fit into a DIP package that was plug-compatible with the original processor.

6502 in popular culture

In the science fiction movie ''The Terminator'' (1984), starring Arnold Schwarzenegger, the audience at one point is treated to a view through the T-800 Model-101 robot character's eye/camera display with some 6502 assembly/machine code program fragments scrolling down the screen. The program was listing the Apple DOS 3.3 disassembled program listing. Also shown is the output from a run of an Apple checksum program called KEY PERFECT 4.0, published in ''Nibble magazine''.

Bender, a fictional android "industrial robot" manufactured in 2998 CE, and a main character in the animated TV series ''Futurama'' created by Matt Groening, was revealed to have a 6502 as his "brain" in the episode "Fry and the Slurm Factory". David X. Cohen (the head writer and executive producer of ''Futurama'') has claimed in an interview with IEEE Spectrum that he and friends David Borden and David Schiminovich wrote an assembly language compiler (for a custom language they created named "FLEET") for the Apple II Plus, which uses the 6502, while at high school, and confirmed that this led him to include the reference in the show.

See also

Lisa assembler

MOS Technology 6502-based home computers

Interrupts in 65xx processors

Vasm, a free assembler

References

A comparison of the Motorola M6800 and the MOS Technology MCS6501/MCS6502 microprocessors. It was written in August 1975, about a month before the 6500 family was introduced at the WESCON trade show in San Francisco CA., (September 16-19, 1975)

External links

General information:

6502.org - the 6502 microprocessor resource – Repository and portal (Mike Naberezny)

650x information – Concise description, photos of MOS and second source chips; at cpu-collection.de (Dirk Oppelt)

a2DMAMagic – The secret, transparent, high-throughput 6502 DMA channel (by Jorge Chamorro Bieling)

mdfs.net – 6502 instruction set

Instruction set features:

6502 - the first RISC µP – With link to concise 6502 programming chart in PDF (Eric Clever)

Emulators and simulators:

Visual Transistor-level Simulation of the 6502 CPU

List of 6502 software emulators – At Zophar's Domain (Sam Michaels)

6502 simulator for Windows – At Dan Boris' homepage hosted by The Atari Gaming Headquarters

Web-based 6502 compatible compiler and emulator written in JavaScript – by Stian Søreng

Early 6502 computers:

Apple I Owners Club – Hosted by the Applefritter site (Tom Owad)

KIM-1 schematics – At The Obsolete Technology Website (anonymous collector)

Rockwell AIM 65 – The Old Computer Hut

Hardware accelerators:

6502 accelerator information – At the Apple II History website (Steven Weyhrich)

"Underneath the Hood of the SuperCPU" – By Jim Brain, in ''C=Hacking'', Issue #12, Version 1.3, March 1996 (search for "@(#)cmdcpu")

Hardware:

The Western Design Center, Inc. (WDC) – home of the 65xx brand CMOS microprocessors.

Category:1975 introductions

ca:MOS Technology 6502 cs:MOS Technology 6502 da:MOS Technology 6502 de:MOS Technology 6502 el:MOS Technology 6502 es:MOS 6502 fr:MOS Technology 6502 ko:MOS 6502 hr:MOS 6502 it:MOS 6502 la:MOS Technology 6502 hu:MOS Technology 6502 nl:MOS 6502 ja:MOS 6502 no:MOS Technology 6502 nn:MOS Technology 6502 pl:MOS Technology 6502 pnt:MOS Technology 6502 pt:6502 ru:MOS Technology 6502 sh:MOS 6502 fi:MOS 6502 sv:MOS Technology 6502 zh:MOS 6502

Bill Budge (born c. 1954) is a computer game programmer and designer. His two main claims to fame are 1981's ''Raster Blaster'' and 1983's ''Pinball Construction Set''. Both these games were released originally for the Apple II.

Budge says he became interested in computers while obtaining a PhD at UC Berkeley. He purchased an Apple II and began writing games. He enjoyed it so much that he dropped out of school and became a game programmer.

Early games

Budge's first game was a ''Pong'' clone, called "Penny Arcade", which he wrote using his own custom graphics routines. He traded the completed game to Apple Computer for a Centronics printer. While a graduate student in Computer Science at UC Berkeley, he went on to make other games, which he tried to market commercially. Teaming up with a floppy disk drive salesman who traveled from store to store, he and the salesman agreed to split profits of selling his games 50/50. Budge was shocked when he got his first check for USD$7,000.

Budge then proceeded to write fast graphics libraries for game programmers. He stated that was where his real love was: :"I wasn't that interested in playing or designing games. My real love was in writing fast graphics code. It occurred to me that creating tools for others to make games was a way for me to indulge my interest in programming without having to make games".

''Raster Blaster'' and ''Pinball Construction Set''

Budge first became interested in writing a pinball game while working for Apple in 1981. There was a pinball craze going on among the engineers there and it occurred to him that a pinball game would be a fun programming challenge. At that point he wrote ''Raster Blaster'', which presented some significant challenges under the Apple II. Things like physics and collision detection were brutal with the limited facilities of the Apple II's 1 MHz 6502 processor.

From this initial pinball game, it was a small step to writing an entire construction set. Budge notes that it also required him to write a mini-paint program, a mini sound editor and save/load systems. Some of the components he already had, which he developed for ''Raster Blaster''.

After writing ''Raster Blaster'', Budge founded his own company, BudgeCo, taking over the responsibility of what his publishers were doing. He printed copies of his games and put them in a Ziploc bag with a photocopy of the game's instructions.

By 1983, however, the computer game publishing arena had become too complex for Budge's taste, who did not really want to be an entrepreneur. When he was approached by Electronic Arts (EA) founder Trip Hawkins (whom he had met when they both worked at Apple) to publish his games, he discussed the idea with Steve Wozniak and willingly signed on. With EA's distribution, ''Pinball Construction Set'' eventually sold 300,000 copies over all platforms. Budge's name became well-known among gamers, because of EA's "rockstar" promotion of game designers (other designers who received similar treatment were Dan Bunten, Anne Westfall, and Jon Freeman).

Part of EA's rockstar promotion was sending their programmers out on autograph tours. Budge was included in this and went around signing the "album cover" packages of his game published by EA.

They also assembled several developers and hired a Hollywood photographer for taking a photograph in rockstar pose which led to EA's famous ''We See Farther'' advertising poster.

After ''PCS'', Budge toyed with the idea of creating ''Construction Set Construction Set'' but abandoned the idea after determining it was too complex a concept. He did, however, create the ''3-D Graphics Tool'', a program that allowed rudimentary creation of wire-frame graphical images for use in games or other applications.

''Pinball Construction Set'' is an inductee in ''GameSpy'''s Hall of Fame.

''MousePaint''

Budge wrote MousePaint, which was a program for the Apple II similar to the Macintosh program ''MacPaint''. ''MousePaint'' was bundled with an ''AppleMouse II'' and interface card for the Apple II. Apple Computer released the mouse and software in May 1984.

After EA

Budge left the game industry to semi-retirement in the mid-1980s in the San Francisco Bay Area.

Budge returned in the 1990s after deciding that he only liked working when he enjoyed the work. By this point he had decided that he liked game programming as long as he was developing something cutting-edge. To this end, Budge ported ''Pinball Construction Set'' (under the title ''Virtual Pinball'') to the Sega Genesis, one of the hottest platforms at the time.

Shortly afterward, Budge went to go work for 3DO, creating a 3D engine for ''Bladeforce''. He remained with the company for nine years until its demise in 2003. Budge returned to EA but stayed for less than two years. He joined Sony Computer Entertainment in 2004 as Lead Tools Programmer. Bill left Sony after 6 years for Google in 2010.

Budge and his wife live in the San Francisco Bay Area and have two children.

Awards

In 2008, ''Pinball Construction Set'' was honored at the 59th Annual Technology & Engineering Emmy Awards for "User Generated Content/Game Modification". Budge accepted the award.

On February 10, 2011, Budge was the second recipient of the Pioneer Award from the Academy of Interactive Arts & Sciences.

References

External links

Budge entry from the NNDB

Budge on a show on video games from 1984

Excerpts from a Nov 1998 interview, with link to complete text

Category:Video game designers Category:Video game programmers Category:Pinball game designers Category:Living people Category:University of California, Berkeley alumni

Michael Abrash is a technical writer specializing in optimization and 80x86 assembly language programming, a reputation cemented by his 1990 book ''Zen of Assembly Language Volume 1: Knowledge.'' The original 8086 processor, the focus of the book, was several generations behind the state of the art by the time the book was published. Related issues were covered in his later book ''Zen of Graphics Programming''. He frequently begins a technical discussion with an anecdote that draws parallels between a real-life experience he has had, and the article's subject matter. His prose encourages readers to think outside the box and to approach solving technical problems in an innovative way.

Game programmer

Before getting into technical writing, Abrash was a game programmer, having written his first commercial game in 1982, ''Space Strike'' for the IBM PC. The game was a PC booter. Other games he wrote were ''Cosmic Crusader'' (1982) and ''Big Top'' (1983) for the same system. After working at Microsoft on graphics and assembly code for Windows NT 3.1, he returned to the game industry in the mid-1990s to work on ''Quake'' for ''id Software''. Meantime, Abrash also worked on the popular game ''Doom''. Some of the technology behind ''Quake'' is documented in Abrash's ''Ramblings in Realtime'' published on the Dr. Dobb's Journal. After ''Quake'' was released, Abrash returned to Microsoft to work on natural language research, then moved to the Xbox team, until 2001.

In 2002, Abrash went to work for RAD Game Tools, where he co-wrote the Pixomatic software renderer, which emulates the functionality of a DirectX 7-level graphics card and is used as the software renderer in such games as ''Unreal Tournament 2004''. At the end of 2005, Pixomatic was acquired by Intel. When developing Pixomatic, he and Mike Sartain designed a new architecture called Larrabee, which now is part of Intel's GPGPU project.

Gabe Newell, CEO of Valve, has said that he has "been trying to hire Michael Abrash forever. ''[...]'' About once a quarter we go for dinner and I say 'are you ready to work here yet?'" In 2011 Abrash made the move to join Valve.

Technical writer

Michael Abrash wrote in the 90s several influential books and other publications which gave him a reputation as good technical writer among the software engineering community. In his 1994 book ''Zen of Code Optimization: The Ultimate Guide to Writing Software That Pushes PCs to the Limit'', Abrash presents principles and theory applicable to today's programmers. The key point of the book was that performance must always be measured, and the book included a measurement tool called the Zen Timer to check if theoretical code optimizations actually worked. The presentation of step-wise program refinement empirically demonstrated how algorithm re-design could improve performance up to a factor of 100. Assembly language re-coding, on the other hand, may only improve performance by a factor of 10. Abrash also showed how elusive performance improvement can be. Simply improving performance in one sub-routine would only expose bottlenecks in other routines and so on. Finally, he demonstrated processor-dependent assembly-based performance improvements by comparing assembly language optimizations across X86 family members.

Another lesson Abrash offered was how hard-earned performance rewards by such micro optimizations could disappear or even make the program execute slower. Abrash was able to gain performance by carefully counting clock cycles of each instruction and ordering instructions in such a way that they used a minimal number of clock cycles. However, the number of clock cycles per instruction changed with new implementations of the x86 architecture and, as a result, his performance gains were lost from one generation to the next. For example, the bit-oriented "XOR EAX, EAX" (example in Intel assembler syntax) instruction was the fastest way to set a register to zero in the early generations of the x86, but most code is generated by compilers and compilers rarely generated XOR instructions, so the IA designers decided to move the frequently occurring compiler generated instructions up to the front of the combinational decode logic, making the literal "MOV EAX, 0" instruction execute faster than the XOR instruction. Still, carefully hand optimized assembler code will in general perform well on later x86 processors, even without retuning for the new architecture. The reason is that the optimization policies change only gradually between the architectures, so that many optimization assumptions valid for the original architecture still hold on the new architectures, for example "integer arithmetic is significant faster than floating point arithmetic" or "minimize memory accesses for maximum register usage".

In the year 1997 Abrash published the ''Graphics Programming Black Book'', primarily based on his experiences and optimizations with the Quake 1 graphic subsystem.

References

External links

''Ramblings in Realtime'' by Michael Abrash, detailed description of ''Quake'''s graphics engine programming (PDF version)

''Graphics Programming Black Book'' by Michael Abrash for download alternative source

Category:American technology writers Category:Video game programmers Category:Living people Category:Microsoft employees

zh:迈克尔·亚伯拉什

Coordinates	40°42′15.0″N73°55′4.0″N
name	Cee Lo Green
background	solo_singer
birth name	Thomas DeCarlo Callaway
alias	Cee Lo Green, Cee Lo
born	May 30, 1974Atlanta, Georgia, US
instrument	Vocals, piano
genre	Soul, hip hop, neo soul, R&B;, funk, alternative hip hop, hip hop soul
occupation	Singer-songwriter, rapper, record producer, actor
years active	1992–present (group)2002–present (solo)
label	Arista, Elektra
associated acts	Gnarls Barkley, Goodie Mob, Kid Cudi, OutKast, Jazze Pha, Bruno Mars
website	}}

Thomas DeCarlo Callaway (born May 30, 1974), better known by his stage name Cee Lo Green, is an American singer-songwriter, rapper, record producer and actor. He originally came to prominence as a member of the southern hip hop group Goodie Mob, later launching a critically acclaimed solo career and forming Gnarls Barkley with DJ/producer Danger Mouse.

Internationally, Cee Lo is best known for his hip hop work and Gnarls Barkley's 2006 worldwide hit "Crazy", which reached number one in various singles charts worldwide, including the UK. In the United States, "Crazy" reached number two on the Billboard Hot 100. Parent album ''St. Elsewhere'' was also a hit, reaching number one on the UK Albums Chart and number four on the US ''Billboard'' 200 album charts. Gnarls Barkley's second album, internationally less successful, ''The Odd Couple'' (2008) missed the top ten in both the UK and US, where it charted at number 12 in the US, and 18 in the UK.

Cee Lo, taking a break from recording with Gnarls Barkley, released the single "Forget You!" on August 19, 2010 as a solo recording artist. The song was an instant hit, reaching the top spot in the UK and the Netherlands and charted at number two on the US ''Billboard'' Hot 100. The parent album, ''The Lady Killer'' (2010) saw similar success, peaking within the top five of the UK Album Charts and debuting within the top ten on the ''Billboard'' 200 album charts, and received a Gold certification from the BPI in the UK shortly after its release. His second single "It's OK" was a hit in Europe and the third single, "Bright Lights Bigger City" has also seen similar charting success. Cee Lo is currently a vocal coach on the NBC reality talent show ''The Voice'' with Adam Levine, Christina Aguilera, and Blake Shelton.

Early life

Cee Lo Green was born Thomas DeCarlo Callaway in Atlanta, Georgia and graduated from Benjamin E. Mays High School in Southwest Atlanta. Both of his parents were ordained ministers and he started his music career in his church. His father died when he was two years old. His mother, Sheila J. Tyler-Callaway, was also a volunteer firefighter. She was involved in a car crash, leaving her paralyzed, and died two years after the accident. At the time, Cee Lo was 18 years old and his career with Goodie Mob had just begun taking off. His mother's death led Cee Lo into depression, as is reflected in various songs throughout his career, including "Free" by Goodie Mob, songs on ''St. Elsewhere'', and on ''The Odd Couple'' ("She Knows", "A Little Better"). Cee Lo also expresses his love for his mother in the song "Guess Who" from Goodie Mob's ''Soul Food'' album.

Music career

Goodie Mob

Along with Big Gipp, T-Mo, and Khujo, Cee Lo was an original member of the Atlanta hip-hop group Goodie Mob. He is the youngest of the four. The Goodie Mob were a part of the Atlanta rap collective the Dungeon Family, which also included OutKast. The group released their debut album, ''Soul Food'' in 1995. The album received much critical praise as a pioneering record for the then emerging Southern rap scene. It featured a distinctive soulful southern sound by production team Organized Noize, who had also produced OutKast's debut ''Southernplayalisticadillacmuzik''. Cee Lo got considerable praise for his rapping and singing of hooks, particularly on the hit singles "Cell Therapy" and "Soul Food".

The group's second album, ''Still Standing'' came out in 1998 and also received much critical praise. Its commercial performance was slightly lower than the group's previous effort however. At this time, Cee Lo focused primarily on rapping over singing. While he did frequently sing hooks and did some singing, at this point he was a rapper first and foremost. Cee Lo took more creative control on the group's next album, ''World Party''. Released in 1999, this album was more of a party record than the group's previous output, getting away somewhat from their socially conscious lyricism.

During the making of the album ''World Party'', Cee Lo left the group to pursue a solo career under Arista and the remaining members continued to perform together under the Goodie Mob name with Koch Records. They did however collaborate in combinations in the Dungeon Family album ''Even in Darkness''. Although the next Goodie Mob album seemed to mock Cee Lo with its title, ''One Monkey Don't Stop No Show'', the group expressed that it was more of a jab at Arista and the music industry as a whole.

In 2005, Cee Lo and Big Gipp were both noted in interview. No title or release date have been given for the new project. The song "Hold On" from Big Boi of OutKast's Got Purp? Vol 2 album was the first newly recorded Goodie Mob song with all four members since ''World Party''. (Khujo later revealed to fans at an album signing for his new album "Mercury", that the song "Hold On" was originally recorded in 1995 before ''Soul Food'' was released.)

Santana

In 1999, Cee Lo, credited as "Cee-Lo" was one of ten famous guest musicians who contributed to the highly successful Santana album ''Supernatural''. Lauryn Hill wrote "Do You Like The Way," and the two of them trade off on lead vocals.

Solo career

Cee Lo's Arista career was short-lived, as he was dropped after only two albums due to low record sales. His first album, ''Cee-Lo Green and His Perfect Imperfections'', was heavily in the vein of various other Dungeon Family releases, with southern soul/funk/jazz backings produced solely by himself and boasting appearances by fellow Dungeon Fam members Big Gipp and Backbone. The album explored his departure from Goodie Mob and his solo growth in the song "El Dorado Sunrise (Super Chicken)", as well as socio-political issues, and showcased his singing. The album did not sell very well, but Cee Lo achieved some airplay with the single "Closet Freak".

His second Arista album, ''Cee-Lo Green... Is the Soul Machine'' brought a more branched-out sound and more deeply explored southern rap music. This is evidenced by collaborations with Ludacris, T.I., and Pharrell and production from Timbaland, The Neptunes, and Jazze Pha among others. The only other Dungeon Family member that appeared on his second release was Big Rube. This album saw Cee Lo delve into other styles besides traditional rap. Timbaland proved to be Cee Lo's single producer as their song "I'll Be Around" received mild airplay. They performed the single on an episode in the second season of ''Chappelle's Show''. "The One" featuring Jazze Pha and T.I. was also released as a single. On the heels of the success of Gnarls Barkley, Arista released a 17-track greatest hits collection of Cee Lo songs, ''Closet Freak: The Best of Cee Lo Green the Soul Machine''. It features predominantly Cee Lo solo tracks and several Goodie Mob songs. His new song "What Part of Forever" has been included in ''The Twilight Saga: Eclipse'' Original Motion Picture Soundtrack.

After his second solo album, Cee Lo joined the group Gnarls Barkley (see below) with Danger Mouse, temporarily putting his solo career on hold. He would release two albums with that group, before again releasing solo material in 2010.

On August 19, 2010, Cee Lo released a single "Forget You!" to YouTube ahead of his planned solo album release, due to its partial leak on April 13. "Forget You!" was an instant viral smash hit, registering over two million plays in less than a week. Two weeks later on September 1, Cee Lo released to YouTube an official music video of the song. "Forget You!" made a debut at No.1 on the UK charts, notably beating out "Shame" from the recently reunited Robbie Williams and Gary Barlow. On December 1, 2010, Cee Lo received five Grammy nominations for "Forget You!", which has been certified Gold in the United States and Denmark. The single achieved platinum status in Canada, New Zealand, and the UK; and multi-platinum status in Australia.

When discussing his most recent album, ''The Lady Killer'' (released on November 9, 2010, by Elektra Records and Roadrunner Records), Cee Lo said: "I suppose this is a more clear, concise, consistent, conceptual, entire album. It's a complete thought, because it's written to be like a score. The album's meant to be a motion picture, you know? I've never taken that approach to doing an album before." The album was certified Gold in the UK on December 6, 2010.

Green is touring with an all-female backing band named "Scarlet Fever", performing for ''Taratata'', the BBC, ''Late Show with David Letterman'', W's ''Symmetry Live Concert Series'', ''Saturday Night Live'', the ''Jimmy Kimmel Live!'' special show following the Academy Awards, and many other venues. Green also performed "Forget You", a sanitized version of his hit "Forget You!", with Gwyneth Paltrow and several puppets provided by The Jim Henson Company at the 53rd Annual Grammy Awards on February 13, 2011, a shoutout to Elton John, who wore a very similar costume in a Muppet show performance in 1977. At the 2011 BRIT Awards two days later, he was joined by British vocalist Paloma Faith in another duet of "Forget You". Shortly thereafter, it was announced that Green will be joining Rihanna and J. Cole on the North American leg of Rihanna Loud Tour in the summer of 2011. However, he later dropped out of the tour citing that his busy work schedule which includes his commitment to judging “The Voice”, writing a new book and recording a new album as the reason for his withdrawal. On August 14th 2011, Green performed at WWE SummerSlam performing "Forget You" and the event's theme, "Bright Lights, Bigger City".

Twitter Controversy

On Thursday June 16, 2011, journalist Andrea Swensson of City Pages negatively reviewed one of Green's performances, writing that it "failed to measure up to the fun factor of his recorded material. Green spent most of the set stationed in front of a mic at the center of the stage, barely moving an inch while he sang and flanked by two forgettable back-up singers and a DJ that was all but hidden behind a giant LCD display”. In response, the following day Green tweeted "I respect your criticism but be fair! People enjoyed last night! I'm guessing ur gay? And my masculinity offended u? well fuck U!”. Green promptly received angered responses from some of his followers on Twitter, to which he replied "Apologies gay community! what was homophobic about that?" In a subsequent interview with magazine US Weekly Green stated that his comments were in good fun, adding that "I am not harboring any sort of negative feeling toward the gay community" and that "I am one of the most liberal artists that I think you will ever meet, and I pride myself on that". Green has since deleted the tweets pertaining to this review.

Gnarls Barkley

Along with DJ Danger Mouse, Cee Lo was part of a duo called Gnarls Barkley. They first met when Danger Mouse took second in a talent contest and opened for OutKast and Goodie Mob at a University of Georgia concert in 1998. Afterwards, Danger Mouse gave Cee Lo an instrumental demo tape and told him to call him if he was interested. They did not make contact again until Cee Lo was contacted to be featured in a remix of the Danger Mouse and Jemini song "What U Sittin' On?" from the album ''Ghetto Pop Life''. They worked together again on the 2005 Danger Doom (Danger Mouse and MF Doom collaboration) album The Mouse and The Mask on the song "Benzi Box" where Cee Lo sings the chorus.

Gnarls Barkley first collaborative album, ''St. Elsewhere'', was released on April 24, 2006, in the UK and May 2, 2006, in the United States. ''St. Elsewhere'' entered the charts at No.1 in the UK, as did the first single "Crazy". "Crazy" is the first single to go straight to No.1 in the UK based on digital download sales alone and is ranked by Rolling Stone as the No.1 song of the decade. The album is Cee Lo's greatest selling venture yet, having shipped over 3 million copies in the United States according to Nielsen SoundScan. A second album by Gnarls Barkley, titled ''The Odd Couple'', was released in March 2008. Its first single was released in January called "Run (I'm a Natural Disaster)".

Future projects

Cee Lo is collaborating with producer Jazze Pha to release an album called ''Happy Hour'' on Jazze’s record label. The songs "Happy Hour" (as well as the remix with Bun B, Snoop Dogg & Tone Tone), "Man of the Hour", and "Disco Bitch" (featuring The Pussycat Dolls) from the album have already been released as singles and B-sides. Jazze Pha has produced numerous hit singles with many artists, but this project is his rapping and singing debut. Cee Lo is co-producing the album with him, so both artist and producer share equal roles in vocals and production. Also, Melody Thornton confirmed that she is currently in the studio with Cee Lo working on her solo album. In 2010, he recorded a song for the ''Sex and the City 2'' soundtrack which reached number 9 in the charts and was written by him and produced by T-Pain which is called "Language of Love". He along with The Red Hot Chili Peppers and OneRepublic frontman Ryan Tedder were rumored to be appearing on British DJ Paul Oakenfold's upcoming album.

Television and film career

Cee Lo, along with the rest of the Goodie Mob, had a cameo in the 1999 film ''Mystery Men'' as a member of the Not So Goodie Mob. He also has done voice acting work, voicing Prime Cut Miggity-Mo' Macdaddy Gizzabang Doggy Dog Dog on the ''Brak Show'' episode "Brakstreet" in 2002, Frank and Buddy Z ''Class of 3000'''s Christmas special and as Godzilla in the ''Robot Chicken'' episode "Squaw Bury Shortcake" in 2007, and Rev. Rollo Goodlove in the ''Boondocks'' episodes "The S-Word" and "The Hunger Strike" in 2008. In 2010, he appeared in T-Pain's ''Freaknik: The Musical'' as Light Skin.

On January 15, 2011, Cee Lo both acted and performed on NBC's ''Saturday Night Live'' hosted by Gwyneth Paltrow, who, in November 2010, covered his song "Forget You" on an episode of ''Glee''.

Cee Lo is currently one of the coaches for contestants on the singing TV show ''The Voice''.

Personal life

Cee Lo has described himself as being a "goon" in his youth.

Cee Lo was married to Christina Johnson until they divorced in 2005. Together they have a son Kingston; and Cee Lo was a stepfather to Christina's daughters, Sierra and Kalah.

Discography

''Cee-Lo Green and His Perfect Imperfections'' (2002)

''Cee-Lo Green... Is the Soul Machine'' (2004)

''The Lady Killer'' (2010)

Awards and nominations

|- | rowspan="3"| 2011 | rowspan="2"| Brit Awards | ''Best International Album'' | |- | ''Best International Male'' | |- | BET Awards | ''Best Male R&B; Artist'' |

Grammy Awards

|- | style="text-align:center;" rowspan="4"| 2007 ||style="text-align:left;" rowspan="2"|"Crazy" || Record of the Year || |- | Best Urban/Alternative Performance || |- |style="text-align:left;" rowspan="2"|''St. Elsewhere'' || Album of the Year || |- | Best Alternative Music Album || |- |style="text-align:center;" rowspan="2"| 2009 || "Going On" || Best Pop Performance by a Duo or Group with Vocals || |- | ''The Odd Couple'' || Best Alternative Music Album || |- |style="text-align:center;" rowspan="4"| 2011 ||style="text-align:left;" rowspan="4"|"Forget You" || Record of the Year || |- | Song of the Year || |- | Best Urban/Alternative Performance || |- | Best Short Form Music Video ||

References

External links

Cee Lo Green on BBC Music

Official Jazze Pha & Cee Lo website

Cee Lo Green Storytellers on VH1

Category:1974 births Category:Living people Category:African American singers Category:American funk musicians Category:American male singers Category:American pop singers Category:American tenors Category:American rhythm and blues singers Category:American singer-songwriters Category:American soul singers Category:Dungeon Family Category:Gnarls Barkley members Category:Hip hop record producers Category:Rappers from Atlanta, Georgia Category:Neo soul singers Category:BRIT Award winners Category:Grammy Award winners Category:The Voice judges

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