Rambus Memory Upgrades

Direct Rambus DRAM (DRDRAM, Rambus DRAM or RDRAM) is a type of synchronous dynamic RAM, built by the Rambus Corporation. Rambus shows a small increase in manufacturing complexity (adding a memory controller on each memory chip), cost (including high license fees), heat output, and latency compared with other contemporary standards. RDRAM’s larger die size – required to house the added interface – results in a 10-20% price premium at 16M densities and adds roughly a 5% penalty at 64M and is often met with criticism. Instead of 64-bit bus in contemporary SDRAM DIMM, RDRAM’s memory module only runs on 16-bit bus yielding an 800 MHz clock rate. Rambus memory utilizes double sampling, meaning data is transferred on both the rising and falling edges of the clock signal.

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History

Beginning in 1996, Rambus’s RDRAM appeared in three video game consoles starting with Nintendo 64. RDRAM’s simplistic design (narrow bus allowing circuit board designers to simplify their design techniques) allowed N64 to command a large memory bandwidth while maintaining a lower cost – 4 MB RDRAM paired with a 500 MHz clock on a 9-bit bus, yielding 500 MB/s bandwidth cooled by a passive heatspreader assembly. However, the memory was disfavored for its high random access latencies. Sony also utilized RDRAM in their PlayStation 2 – 3200 MB/s available bandwidth utilizing a dual-channel configuration with 32 MB of memory. The PlayStation 3 packs 256 MB of Rambus XDR DRAM (a successor to RDRAM) on a 64-bit bus at 400 MHz with an octal data rate yielding a clock rate of 3.2 GHz, permitting a sizable 204.8 Gbit/s (25.6 GB/s) bandwidth.

In 1999 the first PC motherboards with RDRAM support hit the market, supporting PC-800 RDRAM which ran at 400 MHz and yielded 1600 MB/s of bandwidth on a 16-bit bus. Similar to a DIMM (dual in-line memory module), it was packaged as a 184-pin RIMM (Rambus in-line memory module) form factor. The clock rate was multiplied by two (because of the DDR operation and marketing reasons); the resulting 400 MHz Rambus standard was named PC-800. This boasted much higher speeds than the previous standard, PC-133 SDRAM, which ran at 133 MHz and yielded 1066 MB/s of bandwidth on a 64-bit bus utilizing a 168-pin DIMM form factor. Introduced in 2000, PC-2100 DDR SDRAM ran a clock rate of 133 MHz, yielding 2100 MB/s on a 64-bit bus utilizing a 184-pin DIMM form factor. PC-800 RDRAM’s latency operated at 45 ns, which was greater than other comparable DRAM technologies.

Intel added support for dual-channel PC-800 RDRAM when it introduced the Intel 840 (Pentium III), Intel 850 (Pentium 4), and Intel 860 (Pentium 4 Xeon) chipsets – doubling bandwidth to 3200 MB/s by adding a larger 32-bit bus width. Subsequently in 2002 the Intel 850E chipset (which launched PC-1066 RDRAM) raised total dual-channel bandwidth to 4200 MB/s. The same year Intel released the E7205 Granitebay chipset, which christened dual-channel DDR support for a total bandwidth of 4200 MB/s, yielding a slightly lower latency than comparable RDRAM.

Desktop Memory Installation

Laptop Memory Installation