[clug] OT: DDR RAM and FSB speed

Steve Walsh steve at nerdvana.org.au
Mon Jan 24 02:57:49 GMT 2005

He's Close, but he's also very very wrong.

DDR400 is hit twice in a clock cycle, so whilst it is hit only at 200Mhz,
due to the fact it loads twice per clock cycle it is effectively running at
400Mhz. He's been caught by the SDR/DDR conversion.(DDR266 runs at 133, DDR
400 runs at 200, but 200Mhz is a lower number than 266, so therefore it all
works out in his head) Thankfully, the board in question should auto detect
that it has slower ram and run accordingly.

The problem he probably really has (and this is one I've been caught with),
is DDR400 ECC is few and far between, and a lot of the Xeon boards only like
ECC ram. It's probably more a case that PC2100 ECC is cheaper for him than
DDR400 ECCram.



-----Original Message-----
From: Brett Worth
Sent: Monday, 24 January 2005 1:00 PM
To: linux
Subject: [clug] OT: DDR RAM and FSB speed

I'm getting a vendor to quote me on a Dual Xeon system and asked for 8GB of
PC3200 RAM given that the MB and Xeons are spec'd with a 400Mhz FSB.

The quote came back with PC2100 (266Mhz) on it and when I queried the
salesman he said that it never gets hit harder than 200Mhz.  Is this true?
Could memory interleaving make this possible?


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