PC2 6400 cas lat: 5 or PC2 5400 cas lat: 4

Catsonar

Catsonar

[H]ard|Gawd
Joined
Oct 3, 2003
Messages
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Hi everyone,


I have been debating if rather I should send my ram back and get a lower latency ram slightly running Mhz wise a bit slower. I currently have this ram:



http://www.newegg.com/Product/Product.aspx?Item=N82E16820141340

But I was wondering if i should go ahead and get this:


http://www.newegg.com/Product/Product.aspx?Item=N82E16820231154

It has cas latency of 4 compared to the PQI which is rated at 5. Is it a big difference in performance? From my understanding it all depends on what programs will take advantage of the latency while other will prefer bandwith. I went with PQI cause its running at 800mhz and the CPU has a FSB of 800, so I figured that would pair great with this ram. Is it true that lower cas latency will be prefered with games? i would like to hear your opinions on this subject. Thank you.
 
At a given bus speed, lower latency is better, but normally you would prefer a higher bus speed to lower latency. So RAM at 800 at latency 5 is better than RAM at 700 with latency of 4. Don't go with a memory divider just to get the lower latency.

Actually, is that an Intel CPU? If so the 800 FSB is really 200, because the Intel bus is quad pumped, while the RAM is double. So if your CPU is running on an 800 FSB (like an E4300 or something) that is really 200 Mhz, which is only 400 DDR for the RAM. If that is the case then you are really underspeeding the RAM, and a lower latency is probably better. Of course, at such a low speed (for the RAM) you can almost certainly tighten the timings of what you have now to run at latency 4 as well - it is rated to run 400 (800 DDR) at CAS 5, so 200 (400 DDR) should be easy at CAS 4.
 
Short answer: you did well.

Explanation: Since this is for a laptop, the rules change a bit. The motherboard is locked so that the RAM will run at whatever SPD timings it has programmed into it. It's best to get fast memory because it has the speed advantage if the motherboard supports it. Also, it'll downclock if it doesn't and many times the lower clocks also have the tighter timings (9/10 times anyway). You can confirm this by running CPU-Z when you install it: check the memory tab and see what speed/timings are programmed into it. Anyway, the speed advantage offers more performance than the lower latencies will.
 
Mr. K6 said:
Short answer: you did well.

Explanation: Since this is for a laptop, the rules change a bit. The motherboard is locked so that the RAM will run at whatever SPD timings it has programmed into it. It's best to get fast memory because it has the speed advantage if the motherboard supports it. Also, it'll downclock if it doesn't and many times the lower clocks also have the tighter timings (9/10 times anyway). You can confirm this by running CPU-Z when you install it: check the memory tab and see what speed/timings are programmed into it. Anyway, the speed advantage offers more performance than the lower latencies will.
Click to expand...

One possible hiccup with this:

The Dell M1530 laptop only supports up to DDR2-667 (PC2-5300) memory speed. Some DDR2-800 (PC2-6400) memory modules have no SPD information for any speed other than DDR2-800 speed, and thus would result in the M1530 refusing to even POST because the BIOS could not detect a valid SPD on the memory module. And even if you use DDR2-667 memory, the Dell will only use CAS 5 latency regardless of the info on its SPD (as long as any info at all whatsoever is programmed @ DDR2-667 speed).

And no name-brand laptop has any provision at all whatsoever to manually adjust the memory speed or timings.
 
E4g1e said:
One possible hiccup with this:

The Dell M1530 laptop only supports up to DDR2-667 (PC2-5300) memory speed. Some DDR2-800 (PC2-6400) memory modules have no SPD information for any speed other than DDR2-800 speed, and thus would result in the M1530 refusing to even POST because the BIOS could not detect a valid SPD on the memory module. And even if you use DDR2-667 memory, the Dell will only use CAS 5 latency regardless of the info on its SPD (as long as any info at all whatsoever is programmed @ DDR2-667 speed).

And no name-brand laptop has any provision at all whatsoever to manually adjust the memory speed or timings.
Click to expand...

What???? Supports up to 667mhz???? Where did you get that info from? Is this true. Google'd to see if this is true and couldn't find anything. Let me know
 
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