DDR - CAS 2 or 2.5 -does it really matter?

I have a question concerning CAS-latencies. I checked the sites of Crucial, Infineon, Kingston, Corsair and Mushkin for their memory specs, only Infineon and Mushkin give more information than simply the CAS-latency. Seems that their top-line DDR-2100 RAM has 2-3-3 specs, their ordinary DDR rams has 2.5-3-3 specs.
As I understand it, the difference in CAS-latencies comes only in to play when doing an out-page read and in this case
the RAS-TO-CAS-delay (3ticks) and the precharge-delay (3ticks) also come in to play. So doing an out-page read will cost in CAS2 8 ticks, in CAS2.5 8.5 ticks.
So the question is: is this small decrease worth the extra money and time finding CAS2-memory?
8 answers Last reply
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  1. youll also notice on mushkins website that they rate their hi perf DDR (up to 256mb) is rated 2/2/2. theyre 512 dimms are rated 2/3/3. i have mushkin hi perf DDR (256mb)...thought id point that out to you =)
  2. You are right, overlooked this. Any idea why their 512Mb-DIMMs are rated lower. And are their any other companies that you know of that produce 2-2-2 DDR rams?

    <P ID="edit"><FONT SIZE=-1><EM>Edited by outer_spacer on 02/17/02 04:37 PM.</EM></FONT></P>
  3. corsair makes pc 2700 at 2-2-2 but it is very costly 137.00 for 256 mb at newegg

    lagger

    <b><font color=blue>Checking under my north AND south bridges for trolls</font color=blue>
  4. ...but is this CL2-2-2 stuff worth shelling out the extra dough?
  5. if you are obsessive-compulsive about getting every last drop out of you systems like me... yeah.. otherwise probably not

    lagger

    <b><font color=blue>Checking under my north AND south bridges for trolls</font color=blue>
  6. well there is aperformance increase, not much. one thing you should keep in mind is if you use two sticks of cas2 it will act like 2.5. ozc makes pc3000. rated at 2.5-3-3. the bandwith it offers is the biggest thing about it. bandwith is better.

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  7. why do 2 sticks CAS2 ddr-ram acts as CAS2.5? Seems to me that CAS has nothing to do with bank selection.
  8. hard asss question man. and i'm not very good at explaining this.

    the northbridge on the mobo is the problem. memory tests will show this as well.

    i'll see if i can get more detailed on this.

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