Posted: 11/22/2002 10:14:12 AM EDT
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I'm looking at building a new computer for myself, and I've never understood what all these abbreviations mean for computer memory... Things like this: CL=2.5 • Unbuffered • Non-parity • 6ns • 2.5V Is unbuffered the same as non-ECC? What numbers should I be looking for? I was planning on building a really fast system with the new DDR3200. Crucial, who I normally go to, doesn't seem to sell it yet. Any ideas for other manufacturers? Who can I trust and who should I look out for? Thanks |
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Try Corsair memory [url]www.corsairmicro.com[/url]. They have the new XMS3500. CL = CAS Latency Measure of clock cycles. Smaller = better. ns = nanoseconds. The inverse of the clock freq. Smaller = better Buffered != ECC ECC = error checking and correcting. good to have, but more $ Buffered Your motherboard dictates whether you need buffered or unbuffered. |
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Non-parity memory modules typically come with 8 memory chips. Modules with parity checking add a ninth memory chip that keeps track of the parity of the data in the other 8 chips as an error correction mechanism. 2.5V means that the power supply voltage to the memory chips is 2.5 volts. That's standard for DDR memory. As TheRicker explained, 6 nanoseconds is the clock period, which is the inverse of the clock frequency. 1 / 6ns = 166.67 MHz, 1 / 7.5ns = 133.33 MHz, and 1 / 5ns = 200 MHz. Since DDR (Double Data Rate) memory transfers data twice per clock cycle, on both the rising and falling edge of the clock, 2*133MHz = DDR266, 2*166MHz = DDR333, and 2*200MHz = DDR400. So 7.5ns => DDR266, 6ns => DDR333, and 5ns => DDR400. Since there are 8 chips each transferring 2 bits per clock cycle, 133MHz * 16bits = 2133 Mbits/sec (PC2100), 166MHz * 16bits = 2667 Mbits/sec (PC2700), and 200MHz * 16bits = 3200 Mbits/sec (PC3200). CAS = Column Address Strobe. When the memory strobes the column address to begin the read process, the data isn't valid to be read at the output of the memory until a short time later. CAS latency tells you how many clock cycles the memory has to wait for valid data after sending the address. For CL = 2.5 and a clock period of 6ns, the read latency is 2.5 * 6ns = 15 nanoseconds. |
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Quoted: Things like this: CL=2.5 • Unbuffered • Non-parity • 6ns • 2.5V What numbers should I be looking for? You probably should want CL2.0, unbuffered, no parity. [url]http://www.tomshardware.com/mainboard/02q4/021111/index.html[/url] Look at the various benchmarks, decide which reflect your computer usage, and decide for yourself. Corsair part#s and rough prices i have on hand: 256MB 333Mhz CL2.0 CM64SD256-2700 256MB 400Mhz CL2.0 CMX256A-3200C2 512MB 333MHz CL2.5 CM64SD512-2700 512MB 333Mhz CL2.0 CMX512-2700C2 $188 512MB 400Mhz CL2.5 CMX512-3200 512MB 400Mhz CL2.0 CMX512-3200C2 $196 And for the overclocking freaks, $231 for a slice (stick) of heaven: [url]http://www.corsairmicro.com/main/PR_cmx3500c2.html[/url] |