cas2 vs cas3

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i'm thinking of buying ram...considering their prices are really going down.......but i have this dilemma.....what's the difference between cas2 and cas3.....and is DDR memory for AMD based machines only.........any help would be most appreciated...
FORGIVE MY IGNORANCE.....
 

ksoth

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CAS is the latency time for memory access, I believe. Now, 2 is better of course, but prolly not by much. Anyways, I bought a CAS 3 stick of RAM for my machine, and in the BIOS of my mobo I just set the value manually to 2, and it works just fine, 100% stable. Mine is Infineon brand PC133. I'm not sure if all CAS 3 sticks will work at CAS 2, but mine sure did. Anyways, RAM is so cheap now that you might as well get spec CAS 2 (it's only like 5 or 10 bucks more, right?), just incase you know... DDR is currently for special AMD machines right now, but there are DDR chipsets for PIII's and P4's coming out. Not sure when though...
 

ksoth

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For my own interest as well, I did a small set of tests to actually see if there is a difference... I used 3dMark2000, which prolly isn't the best memory speed benchmarker, but is one nonetheless. Well, at CAS 3 I got scores of 5257 and 5277, and CAS 2 I got scores of 5302 and 5296. So, there is definately a difference, but of only around 0.3% to 0.9%. I'm sure that if other tests were run that were specifically made for memory, you'd see more of a difference. But, obviously here there isn't much to look at...
 
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The difference between CAS2 and CAS3 is most apparent during high bandwith transactions, the more latency the less performance. On my system the difference between cas2 and 3 makes a difference of almost 8 frames per second in quake3, which needless to say, is a relatively big difference for something so simple.

By the way, DDR stands for Double Data rate- Its memory that just does its operations twice per clock instead of once (which essential makes the memory nearly twice as fast) But yes, its only supported on Certain Amd systems.
(Intel DDR suport is in the works)

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