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Help and Support Forums => Technical Support => Topic started by: Raptor on June 25, 2004, 05:22:54 PM

Title: Difference in RAM
Post by: Raptor on June 25, 2004, 05:22:54 PM

when I looked at RAM that works on my computer they listed 2 256mb sticks for the same price.
256MB — CT269162 DDR PC2100 CL=2.5 Non-parity
256MB — CT269164 DDR PC2700 CL=2.5 Non-parity

it comes down to DDR PC2100 or DDRPC2700? Whats the difference?

Title: Difference in RAM
Post by: XtrmeJ on June 25, 2004, 05:26:52 PM

Depending on the manufacturer the DDR PC2700 should be a bit faster.

Title: Difference in RAM
Post by: ChasR on June 25, 2004, 06:31:33 PM

PC2100 has a theoretical throughput of 2.1MB/sec and runs syncronous on a 133MHz front side bus (actual rather than effective)
PC2700 has a theoretical throughput of 2.7MB/sec and runs syncronous on a 166MHz front side bus

Title: Difference in RAM
Post by: XtrmeJ on June 25, 2004, 06:34:46 PM

See, I was right! Woot! J/K. :p

Title: Difference in RAM
Post by: ChasR on June 26, 2004, 01:46:43 PM

I should add that FSB is set by the cpu so if its 133, the PC2700 ram will run at PC2100 speed.

Title: Difference in RAM
Post by: zmeg on June 26, 2004, 06:16:01 PM

Ram speed is not limited to CPU speed, it's determined by the FSB speed. normally PC2100 runs at 266Mhz with a 2.5 latentcy and PC2700 runs at 333Mhz with a 2.0 latentcy. Since the PC2700 you listed can't run at 2.0 it's probly junk.

Title: Difference in RAM
Post by: ChasR on June 27, 2004, 12:08:04 PM

zmeg,
I certainly misspoke.  The FSB will be set by the CPU (unless you overide in bois).  So if you have a P4 2.4 A, the actual FSB will be set to 133 MHz, which is 533MHz effective.  The memory will run at an effecvive rate of 266 MHz or PC2100.  No benefit would be gained from using PC2700 ram unless you're going to overclock or the ram will run at lower latencies below its rated speed.