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To: Jdaasoc who wrote (39460)	4/10/2000 6:11:00 AM
From: Bilow	Respond to of 93625

Hi Jdassoc; All those different DDR chips are actually the same die, different final metal layer, I believe. Also note the extensive reply I gave to John on the subject. You wrote: DDR being a 64 bit wide hi speed memory arch. the industry has to decide how to: 1.) - make it work at greater than 133 MHz 2.) - how to design 64 bit memory system with DDR DIMM;s with capacities less than 1GB using 256 Mb chips. As you pointed out much greater than 1 DDR chip design is in consideration/evaluation. (1) That speed, 133MHz, is already fast enough to match RDRAM. RDRAM is already too fast for the computers it hooks up to. The need for higher bandwidth in the future will, no doubt, cause further evolutionary design changes. If the speed of DDR was too slow, they wouldn't have crowded RDRAM out of the graphics market. (2) Your second point is odd. Perhaps you are unfamiliar with the bit versus Byte convention in memory designations, I've noticed you consistently make errors distinguishing these in your posts. "B" means byte, while "b" means bit, and it takes 8 or 9 bits to make a byte. Consequently, 128MB DIMMs are no problem with 256Mb, x16 memory chips. In fact, as I noted in a post a few above, one could use two DDR SGRAM chips to populate a x64 DIMM. That this is not done currently, is not for technical reasons, it is simply for marketing reasons. No one who wants DDR wants such a small memory. (RDRAM is so expensive that users might consider a machine with small amount of memory.) If the two chips are 256Mb, the total memory size is 512Mb = 64MB, much smaller than is required. Alternatively, if you want to spec parts with no wider than the industry standard x16 width, then four parts does it, and the total memory size is 128MB. Future DDR memory chips will be built to x64 and x72 widths, when and as the memory industry requires them. As noted in a post a few previous to this, x64 chips are already out, though only in SDRAM, I believe, and the tiny package is only 22mm long and has only 108 total pins. Clearly there is no reason for granularity to cause problems any time in the next few years for DDR. Getting smaller than 1GB with 256Mb chips is trivial, why do you think that DDR is taking graphics design wins? -- Carl