www.intelciler.com rdram
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www.intelciler.com rdram
Direct Rambus DRAM or DRDRAM (sometimes just called Rambus DRAM or RDRAM) is a type of synchronous dynamic RAM, designed by the Rambus Corporation.
Moreover, if a mainboard has a dual- or quad-channel memory subsystem, all of the memory channels must be upgraded simultaneously. 16-bit modules provide one channel of memory, while 32-bit modules provide two channels. Therefore, a dual channel mainboard accepting 16-bit modules must have RIMMs added or removed in pairs. A dual channel mainboard accepting 32-bit modules can have single RIMMs added or removed as well. Note that some of the later 32 bit modules had 232 pins as compared to the older 184 pin 16 bit modules.rdramrambusmemory.com
The design of many common Rambus memory controllers dictated that memory modules be installed in sets of two. Any remaining open memory slots must be filled with CRIMMs (continuity RIMMs). These sticks provide no extra memory, and only served to propagate the signal to termination resistors on the motherboard instead of providing a dead end where signals would reflect. CRIMMs appear physically similar to regular RIMMs, except they lack integrated circuits (microchips).
PC-800 RDRAM operated with a latency of 45 ns, which was more latency than other comparable DRAM technologies of the time. RDRAM memory chips also put out significantly more heat than SDRAM chips, necessitating heatspreaders on all RIMM devices. RDRAM includes a memory controller on each memory chip, significantly increasing manufacturing complexity compared to SDRAM, which used a single memory controller located on the northbridge chipset. RDRAM was also two to three times the price of PC-133 SDRAM due to a combination of high manufacturing costs and high license fees. PC-2100 DDR SDRAM, introduced in 2000, operated with a clock rate of 133 MHz and delivered 2100 MB/s over a 64-bit bus using a 184-pin DIMM form factor.
When installing multiple RIMMs on a memory channel, performance impact is greater than SDRAM design because the data in the further memory module has to travel across all memory chips installed physically closer to the memory controller, instead of just 1 or 2 chips in production SDRAM motherboards.
With the introduction of the Intel 840 (Pentium III), Intel 850 (Pentium 4), Intel 860 (Pentium 4 Xeon) chipsets, Intel added support for dual-channel PC-800 RDRAM, doubling bandwidth to 3200 MB/s by increasing the bus width to 32-bit. This was followed in 2002 by the Intel 850E chipset, which introduced PC-1066 RDRAM, increasing total dual-channel bandwidth to 4200 MB/s. Then in 2002, Intel released the E7205 Granitebay chipset, which introduced dual-channel DDR support for a total bandwidth of 4200 MB/s, at a slightly lower latency than competing RDRAM.
To achieve RDRAM's 800 MHz clock rate, the memory module only runs on 16-bit bus, instead of 64-bit bus in contemporary SDRAM DIMM. Furthermore, not all production RDRAM modules at the time of the Intel 820 launch could run at 800 MHz; instead, they ran at a slower clock rate.
In 1998, Intel planned to make a $500 million equity investment in Micron Technology, to accelerate the adoption of Direct RDRAM. Other investment included paying $100 million to Samsung Electronics in 1999.
As a transition strategy, Intel planned to support PC-100 SDRAM DIMM on future Intel 82x chipset using Memory Translation Hub (MTH). In 2000, Intel recalled the Intel 820 motherboard with memory translator hub (MTH) because the MTH can, while doing simultaneous switching, produce noise that may cause the computer to hang mysteriously or to spontaneously reboot. Since then, no production Intel 820 motherboards contain MTH.
In 2000, Intel subsidized RDRAM by bundling retail boxes of Pentium 4 CPUs with 2 RIMMs. Intel began to phase out Rambus subsidies in 2001.
In 2003, Intel introduced Intel 865 and Intel 875 chipsets, which were marketed as high end replacement of Intel 850. Furthermore, the future memory roadmap did not include Rambus.
Few DRAM manufacturers have ever obtained the license to produce RDRAM, and those who did license the technology failed to make enough RIMMs to satisfy PC market demand, causing RIMM to be priced higher than SDRAM DIMMs, even when memory prices skyrocketed during 2002. During RDRAM's decline, DDR continued to advance in performance while, at the same time, it was still cheaper than RDRAM. Meanwhile, a massive price war in the DDR SDRAM allowed DDR SDRAM to be sold at or below production cost. DDR SDRAM makers were losing massive amounts of money, while RDRAM suppliers were making a good profit for every module sold. While it is still produced today, few motherboards support RDRAM. Between 2002-2005, market share of RDRAM had never extended beyond 5%.
In 2004, it was revealed that SDRAM manufacturers Infineon, Hynix, Samsung, Micron, and Elpida had entered into a price-fixing scheme. Infineon, Hynix, Samsung and Elpida all entered plea agreements with the US DOJ, pleading guilty to price fixing over 1999-2002. They paid fines totalling over $700 million and numerous executives were sentenced to jail time.
Rambus has alleged that, as part of the conspiracy, the DRAM manufacturers acted to depress the price of DDR memory in an effort to prevent RDRAM from succeeding in the market. Those allegations are the subject of lawsuits by Rambus against the various companies.
Sony uses RDRAM in the PlayStation 2. The PS2 was equipped with 32 MB of the memory, and implemented a dual-channel configuration resulting in 3200 MB/s available bandwidth. The PlayStation 3 utilizes 256 MB of Rambus's XDR DRAM, which could be considered a successor to RDRAM, on a 64-bit bus at 400 MHz with an octal data rate (cf. double data rate) providing a clock rate of 3.2 GHz, allowing a large 204.8 Gbit/s (25.6 GB/s) bandwidth.
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