AMD Am2901: 4-Bit-Slice ALU

Am2900 is a family of integrated circuits (ICs) created in 1975 by Advanced Micro Devices (AMD). They were constructed with bipolar devices, in a bit-slice topology, and were designed to be used as modular components each representing a different aspect of a computer control unit (CCU). By using a bit slicing technique, Am2900 family was able to implement a CCU with data, addresses, and instructions to be any multiple of 4-bits by multiplying the number of ICs. One major problem with this modular technique was it required a larger amount of ICs to implement what could be done on a single CPU IC. The Am2901 chip was the arithmetic-logic unit (ALU), and the "core" of the series. It could count using 4 bits and implement binary operations as well as various bit-shifting operations.

Computers made with Am2900-family chips[link]

There are probably many more, but here are some known machines using these parts:

• The Itek Advanced Technology Airborne Computer (ATAC) used on the Galileo Attitude and Articulation Control Computer System and some Navy aircraft had a 16 register, 16-bit word width assembled from 4-bit-wide 2900 series processors. Four special instructions were added to the Galileo version of the ATAC, and later some chips were replaced with radiation-hardened 2901 chips.^[1]
• Data General Nova 4, which obtained 16-bit word width using four Am2901 ALUs in parallel; one of the boards had 15 Am2901 ALUs on it.^[2]
• Digital Equipment Corporation (DEC) PDP-11 models PDP-11/23, PDP-11/34, and PDP-11/44 floating-point options (FPF11, FP11-A and FP11-F, respectively)^[3][4]
• The Xerox Dandelion, the machine used in the Xerox Star and Xerox 1108 Lisp machine^[5]
• Several models of the GEC 4000 series minicomputers: 4060, 4150, 4160 (four Am2901 each, 16-bit ALU), and 4090 and all 418x and 419x systems (eighteen Am2901 each, 32-bit integer ALU or 8-bit exponent, 64-bit Double Precision floating point ALU) ^[6]
• The DEC KS10 PDP-10 model^[7]
• The UCSD Pascal P-machine processor designed at NCR by Joel McCormack
• A number of MAI Basic Four machines^[8]
• The Tektronix 4052 graphics system computer
• The SM-1420, Soviet clone of PDP-11, used Soviet clone of AM2901^[9] perhaps also used in others.^[10]
• The Lilith computer designed at ETH Zürich by Niklaus Wirth
• Atari's vector graphics arcade machines Tempest, Battlezone, and Red Baron each used 4 Am2901 ICs in their "math box" auxiliary circuit boards.
• Simulation Excel (Sim-X), Oslo, Norway: Typographical workstation / typesetter; one of its four processors was a 16-bit microcoded calculation and transformation engine built from four 2901 slices and one 2910 address sequencer. The Sim-X machine used a 16-bit integer multiplier to optimize graphical transformations.^[11] The machine debuted in 1983 and the company shut down in 1987.
• Eventide H949 Harmonizer; four Am2901 chips (and several microcode PROMs) are used to generate addresses and generate reference voltages for the DAC system - audio was not processed in the 2901 ALU section.
• Many Siemens Teleperm and S5 PLCs used for industrial control were built using the 2900 series.
• AT&T 3B20D Processor^[12]

Members of the Am2900 family[link]

AMD Am2903: 4-Bit-Slice ALU

The Am2900 Family Data Book lists:^[13]

• Am2901 – 4-bit bit-slice ALU (1975)
• Am2902 – Look-Ahead Carry Generator
• Am2903 – 4-bit-slice ALU, with hardware multiply
• Am2904 – Status and Shift Control Unit
• Am2905 – Bus Transceiver
• Am2906 – Bus Transceiver with Parity
• Am2907 – Bus Transceiver with Parity
• Am2908 – Bus Transceiver with Parity
• Am2909 – 4-bit-slice address sequencer
• Am2910 – 12-bit address sequencer
• Am2911 – 4-bit-slice address sequencer
• Am2912 – Bus Transceiver
• Am2913 – Priority Interrupt Expander
• Am2914 – Priority Interrupt Controller
• Am2915 – Quad 3-State Bus Transceiver
• Am2916 – Quad 3-State Bus Transceiver
• Am2917 – Quad 3-State Bus Transceiver
• Am2918 – Instruction Register, Quad D Register
• Am2919 – Instruction Register, Quad Register
• Am2920 – Octal D-Type Flip-Flop
• Am2921 – 1-to-8 Decoder
• Am2922 – 8-Input Multiplexer (MUX)
• Am2923 – 8-Input MUX
• Am2924 – 3-Line to 8-Line Decoder
• Am2925 – System Clock Generator and Driver
• Am2926 – Schottky transistor 3-State Quad Bus Driver
• Am2927/Am2928 – Quad 3-State Bus Transceiver
• Am2929 – Schottky 3-State Quad Bus Driver
• Am2930 – Main Memory Program Control
• Am2932 – Main Memory Program Control
• Am2940 – Direct Memory Addressing (DMA) Generator
• Am2942 – Programmable Timer/Counter/DMA Generator
• Am2946/Am2947 – Octal 3-State Bidirectional Bus Transceiver
• Am2948/Am2949 – Octal 3-State Bidirectional Bus Transceiver
• Am2950/Am2951 – 8-bit Bidirectional I/O Ports
• Am2954/Am2955 – Octal Registers
• Am2956/Am2957 – Octal Latches
• Am2958/Am2959 – Octal Buffers/Line Drivers/Line Receivers
• Am2960 – Cascadable 16-Bit Error Detection and Correction Unit
• Am2961/Am2962 – 4-Bit Error Correction Multiple Buss Buffers
• Am2964 – Dynamic Memory Controller
• Am2965/Am2966 – Octal Dynamic Memory Driver, Image

Many of these chips also have 7400 series numbers such as the 74F2960 / Am2960.

See also[link]

• AMD
• List of AMD Am2900 and Am29000 families
• List of AMD microprocessors
• Bit slicing

References[link]

External links[link]

Wikimedia Commons has media related to: Am29xx

• Introduction to Designing with the Am2900 Family of Microprogramable Bipolar Devices Vol 1 Bitsavers' PDF Document Archive
• Introduction to Designing with the Am2900 Family of Microprogramable Bipolar Devices Vol 2 Bitsavers' PDF Document Archive
• Am29C300/29300 Data Book Bitsavers' PDF document archive
• CPU-World photos of 2900 Family ICs
• Bit-Slice Design: micro-controllers and ALUs. an Introduction to the Am2900 Family
• Bit-Sliced Microprocessor of the Am2900 Family