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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: tejek who wrote (99660)	3/23/2000 9:29:00 PM
From: steve harris	Respond to of 1574493

ted, re:memory Don't tell "Athwipe" pauL, but looks like IBM is dumping Rambust. "IBM Corp. this week put its weight behind DDR, announcing it will utilize it in all of its servers when the technology becomes available. But IBM is interested in DDR for more than servers. It has designed DDR memory modules, known as DIMMs, or dual inline memory module, that will be included in all their PCs and servers." steve dailynews.yahoo.com

To: tejek who wrote (99660)	3/23/2000 9:54:00 PM
From: Dan3	Read Replies (1) \| Respond to of 1574493

Re: I thought DRAM allowed much more bandwidth and speed... SDRAM = synchronous dynamic random access memory RDRAM = rambus dynamic random access memory DDRDRAM = double data rate dynamic random access memory All are dynamic random access memory DRAM, as opposed to SRAM = static random access memory DRAM stores information in capacitors that steadily lose charge and must be periodically refreshed (hence the "dynamic") If a cell is being refreshed when the system tries to access it, the system must wait for the refresh to complete. SRAM is always ready, but uses more power and takes up more chip space. Cache RAM is always SRAM. SDRAM is 64 bits (8 bytes) wide and runs at 100, 133, and (rarely) higher. Data rate is 8 bytes x 100MHZ = 800meg/sec or 8 x 133 = 1064 MB/sec. DDR DRAM is 64 bits (8 bytes) wide and runs at 200, 266, 333, 366, and 400 MHZ data rate (1/2 that speed, double data rate) x 8 or 1,600, 2,128, 2,664, 2,928, and 3,200 MB/sec. DDR DRAM is 16 bits (2 bytes) wide and runs at 566, 712, and 800 MHZ data rate (1/2 that speed, double data rate) x2 or 1,132, 1,424, and 1,600 MB/sec. 2 1,600 MB/sec rambus channels can be combined to equal one 3,200 MB/sec DDR channel. Rambus uses wide data paths on the silicon of the memory chips to allow for 8 cells to be comined into one. The internal data paths on a rambus chip are 128 bits wide. These paths take up more of the chip than other types of DRAM. Rambus chips also have to have logic circuits that collect the data and put it into packets. The logic circuits must run very fast, the rest of the chips doesn't. This size, speed, and complexity increase is why Rambus costs so much more than other types of DRAM. Rambus memory channels are narrower (but faster), so it's easier (and necessary) to put multiple channels on a board. Intel's 840 motherboard uses 2 rambus channels to make up for rambus's 16 bit data bus. Rambus is a high speed serial protocol that adds a brief delay to memory transfers while the chip collects data from 8 cells and combines them into a packet which is then sent along the bus - SDRAM and DDR DRAM connect the chipset directly to the memory cells using a simpler (but slower) protocol. Regards, Dan

To: tejek who wrote (99660)	3/23/2000 10:58:00 PM
From: Petz	Read Replies (3) \| Respond to of 1574493

ted, re:<I thought RDRAM allowed much more bandwidth and speed than even DDR....that article would indicate that DDR and RDRAM are comparable technology. Is that correct?> Do a search for "RAMBUS 600mhz" on pricewatch (without the quotes) and you'll find the cheapest 64M module at $349, and the cheapest 128M module for $641. The actual clock speed of this "600 MHz" RAM is 533 MHz (not kidding!). Since RDRAM has a 16 bit (2 bytes) bus width, it can do 1066 MB/sec peak. The lowly $99 128M PC133 stick I bought last week has a 64 bit (8 bytes) bus that operates at 133 MHz. Its peak bandwidth of 1338 is also 1066 MB/sec peak, exactly the same as that expensive "600 MHz" RDRAM. RAMBUS purists will claim that with RDRAM the peak bandwidth is more likely to be reached in real applications with complex addressing patterns. Maybe so, and maybe not, because RDRAM's latency (delay until you get the first bit of the data) is worst* than even PC100 memory. Petz