In a bid to make its promising XDR memory technology more available on the market, Rambus, a leading developer of interconnection and memory technologies, has reportedly been actively promoting the advantages of its XDR among Taiwan-based producers of dynamic random access memory (DRAM).
So far only Samsung Electronics, Elpida and Qimonda have obtained licenses to manufacture and sell XDR memory chips to interested makers of computers and consumer electronics. The XDR memory is far from being truly affordable now, as 256MB of such memory cost Sony about $48 to install into its PlayStation 3 game console, but with more manufacturers selling it, Rambus hopes that the price will go down.
Rambus believes that “the DRAM sector seems to be underestimating the demand for memory bandwidth in multi-core architectures”, a news-story at DigiTimes web-site claims. The company claims that as the number of processing engines increases, requirements for higher memory bandwidth also go up. For example, single-core Intel Pentium Extreme Edition 3.73GHz had memory bandwidth as high as 8.5GB/s, whereas quad-core Intel Core 2 Extreme QX6850 chip has to be satisfied with 21.3GB/s bandwidth. Moreover, dual-processor and multi-processor systems based on multi-core chips also, in case of Intel Corp.’s architecture, have limited memory bandwidth.
Rambus claims that dual-channel DDR3 memory sub-system at 1.60GHz can provide “only” 25.6GB/s peak memory bandwidth, whereas its XDR2 can scale towards 102GB/s.
What Rambus forgets to note is that modern AMD processors already have integrated dual-channel DDR/DDR2 memory controller, whereas Intel’s code-named Nehalem family of chips are expected to have built-in triple-channel DDR3 controller in the second half of 2008, which means peak bandwidth of up to 38.4GB/s for every physical processor and up to 153.6GB/s of total memory bandwidth for a 4P server system.
Currently only certain Cell processor-based blade servers support XDR memory, whereas the vast majority of XDR output is installed into Sony PlayStation 3 game console. There are no x86 core-logic sets that support XDR memory at the moment.