RDRAM
Rambus DRAM (RDRAM), and its successors Concurrent Rambus DRAM (CRDRAM) and Direct Rambus DRAM (DRDRAM), are types of synchronous dynamic random-access memory (SDRAM) developed by Rambus from the 1990s through to the early 2000s. The third-generation of Rambus DRAM, DRDRAM was replaced by XDR DRAM. Rambus DRAM was developed for high-bandwidth applications and was positioned by Rambus as replacement for various types of contemporary memories, such as SDRAM.
DRDRAM was initially expected to become the standard in
PC main memory
The first
Moreover, if a mainboard has a
Module specifications
Designation | Bus width (bits) |
Channels | Clock rate (MHz) |
Advertised frequency (MHz) |
Bandwidth (MByte/s) |
---|---|---|---|---|---|
PC600 | 16 | Single | 266 | 600 | 1066 |
PC700 | 16 | Single | 355 | 711 | 1420 |
PC800 | 16 | Single | 400 | 800 | 1600 |
PC1066 (RIMM 2100) | 16 | Single | 533 | 1066 | 2133 |
PC1200 (RIMM 2400) | 16 | Single | 600 | 1200 | 2400 |
PC800 (RIMM 3200) | 32 (16×2) | Dual | 400 | 800 | 3200 |
PC1066 (RIMM 4200) | 32 (16×2) | Dual | 533 | 1066 | 4200 |
PC1200 (RIMM 4800) | 32 (16×2) | Dual | 600 | 1200 | 4800 |
PC1600 (RIMM 6400) | 32 (16×2) | Dual | 800 | 1600 | 6400 |
Continuity modules
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 continuity RIMMs (CRIMMs). These modules 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 that they lack integrated circuits (and their heat-spreaders).
Performance
Compared to other contemporary standards, Rambus showed an increase in latency, heat output, manufacturing complexity, and cost. Because of more complex interface circuitry and increased number of memory banks, RDRAM die size was larger than that of contemporary SDRAM chips, resulting in a 10–20% price premium at 16 Mbit densities (adding about a 5% penalty at 64 Mbit).[2] Note that the most common RDRAM densities are 128 Mbit and 256 Mbit.
PC-800 RDRAM operated with a latency of 45
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 bits. This was followed in 2002 by the Intel 850E chipset, which introduced PC-1066 RDRAM, increasing total dual-channel bandwidth to 4200 MB/s. In 2002, Intel released the E7205 Granite Bay chipset, which introduced dual-channel DDR support (for a total bandwidth of 4200 MB/s) at a slightly lower latency than competing RDRAM. The bandwidth of Granite Bay matched that of the i850E chipset using PC-1066 DRDRAM with considerably lower latency.
To achieve RDRAM's 800 MHz clock rate, the memory module runs on a 16-bit bus instead of a 64-bit bus in contemporary SDRAM DIMM. At the time of the Intel 820 launch some RDRAM modules operated at rates less than 800 MHz.
Benchmarks
Benchmark tests conducted in 1998 and 1999 showed most everyday applications to run minimally slower with RDRAM. In 1999, benchmarks comparing the Intel 840 and Intel 820 RDRAM chipsets with the Intel 440BX SDRAM chipset led to the conclusion that the performance gain of RDRAM did not justify its cost over SDRAM, except for use in workstations. In 2001, benchmarks pointed out that single-channel DDR266 SDRAM modules could closely match dual-channel 800 MHz RDRAM in everyday applications.[3]
Marketing history
In November 1996, Rambus entered into a development and license contract with Intel.[4] Intel announced that it would only support the Rambus memory interface for its microprocessors[5] and had been granted rights to purchase one million shares of Rambus' stock at $10 per share.[6]
As a transition strategy, Intel planned to support PC-100 SDRAM DIMMs on future Intel 82x chipsets using Memory Translation Hub (MTH).
In 2000, Intel began to subsidize RDRAM by bundling retail boxes of Pentium 4s with two RIMMs.[9] Intel began to phase out these subsidies in 2001.[10]
In 2003, Intel introduced the 865 and 875 chipsets with dual-channel DDR SDRAM support, which were marketed as high-end replacements of the 850 chipset. Furthermore, the future memory roadmap did not include RDRAM.[11]
Other uses
Video game consoles
Rambus's RDRAM saw use in two video game consoles, beginning in 1996 with the Nintendo 64. The Nintendo console used 4 MB RDRAM running with a 500 MHz clock on a 9-bit bus, providing 500 MB/s bandwidth. RDRAM allowed N64 to be equipped with a large amount of memory bandwidth while maintaining a lower cost due to design simplicity. RDRAM's narrow bus allowed circuit board designers to use simpler design techniques to minimize cost. The memory, however, was disliked for its high random-access latencies. In the N64, the RDRAM modules are cooled by a passive heatspreader assembly.[12] Nintendo also included a provision for upgrading the system memory with the Expansion Pak accessory, allowing certain games to be enhanced with either enhanced graphics, higher resolution or increased framerate. A Jumper Pak dummy unit is included with the console due to the aforementioned design quirks of RDRAM.
The Sony PlayStation 2 was equipped with 32 MB of RDRAM and implemented a dual-channel configuration resulting in 3200 MB/s available bandwidth.
Texas Instruments DLP
RDRAM was used in Texas Instruments' Digital Light Processing (DLP) systems.[13]
Video cards
Cirrus Logic implemented RDRAM support in their Laguna graphics chip, with two members of the family: the 2D-only 5462 and the 5464, a 2D chip with 3D acceleration. Both have 2 MB of memory and PCI port. Cirrus Logic GD5465 has extended 4 MB Rambus memory, dual-channel memory support and uses faster AGP port.[14] RDRAM offered a potentially faster user experience than competing DRAM technologies with its high bandwidth. The chips were used on the Creative Graphics Blaster MA3xx series, among others.
See also
- List of device bandwidths
- SLDRAM, an alternative open standard
References
- ^ rdramrambusmemory.com.
- ^ "Electronic News: Rambus seeks IPO but denies Intel stake - Company Financial Information". www.findarticles.com. Archived from the original on 24 November 2004. Retrieved 12 January 2022.
- ^ Gavrichenkov, Ilya. "ASUS P4B266 Mainboard Review". Xbit Laboratories. Archived from the original on 2016-03-16. Retrieved 17 May 2013.
- ^ Memory Continued. EDACafe Weekly, October 04, 2004.
- ^ What is RDRAM?. Webopedia Computer Dictionary.
- ^ NewsWire Issue 97-8. Archived 2016-03-03 at the Wayback Machine.
- ^ Intel i820 Chipset Review. Tom's Hardware.
- ^ cw062100 – Intel i820 MTH recall. Archived July 24, 2009, at the Wayback Machine.
- ^ Intel chips in for cheaper Pentium 4 PCs. Tech News on ZDNet. Archived 2008-06-21 at the Wayback Machine.
- ^ Intel drops Rambus subsidies. CNET News.com.
- ^ RAM Wars: Return of the JEDEC. Tom's Hardware.
- ^ "Nintendo 64 Tech". n64.icequake.net. Archived from the original on 30 April 2009. Retrieved 12 January 2022.
- ^ Press Release. Rambus Technology XDR.
- ^ "Overclockers.ru: Ретроклокинг: разгоняем память Rambus на платформе Socket 478".