Bluespring
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PC2-4200 CL4 vs PC2-5300 CL5?
I'm an IT Manager and we're about to upgrade a bunch of Dell D820 laptops from 2gb to 4gb(or 3.25gb due to the infamous 32-bit memory limitation problem) for the many vmware machines we run. Memory prices on large memory sitcks seems to have plummeted lately.
As of right now, we have the choice of getting PC2-4200, CL4 2gb dimms, or PC2-5300, CL5 2gb dimms. As it is, most of out laptops already have 1x 2gb PC2-4200 CL4 dimms in them. So my question is, does that increase in CAS latency lower performance to make the clock speed increase negligible? My limited understanding of CAS latency tells me that even though memory timings is a complicated subject, a lower CL is generally better. Also, for dual ranked DIMMs, would it be a problem mixing these clock speed ratings and brands? We want to be sure to get the dual rank performance boost but I wonder just how identical the two chips need to be to ensure this happens.
Thanks for your help.
As of right now, we have the choice of getting PC2-4200, CL4 2gb dimms, or PC2-5300, CL5 2gb dimms. As it is, most of out laptops already have 1x 2gb PC2-4200 CL4 dimms in them. So my question is, does that increase in CAS latency lower performance to make the clock speed increase negligible? My limited understanding of CAS latency tells me that even though memory timings is a complicated subject, a lower CL is generally better. Also, for dual ranked DIMMs, would it be a problem mixing these clock speed ratings and brands? We want to be sure to get the dual rank performance boost but I wonder just how identical the two chips need to be to ensure this happens.
Thanks for your help.
jamietoner
To get the performance enhancement of dual channel memory you'll want the memory to be in matched pairs(same speed, same rank, and same clock latency's). For what memory to get it depends on the FSB of the processor. The PC2 4200 will work better with a 533FSB and the PC2 5300 would work better with a 667 FSB.
In the D820's it makes no sense to use PC2-5300 / 667Mhz... unless they're less expensive.
Reasoning: They will still run at the speed of the PC2-4200's already installed. Your computer is currently configured to use 533MHz Front Side Bus, so there's no benefit to adding the PC2-5300 that runs at 667MHz...
Reasoning: They will still run at the speed of the PC2-4200's already installed. Your computer is currently configured to use 533MHz Front Side Bus, so there's no benefit to adding the PC2-5300 that runs at 667MHz...
Also of note, if you want to use the performance boost, as jamietoner said you'll NEED matched pairs. That doesn't just mean you use one PC2-533MHz module from one company/manufacturer and another PC2-533MHz from another....
Matched pairs means using the exact same part # and preferably from the SAME production run even...
Matched pairs means using the exact same part # and preferably from the SAME production run even...
"In the D820's it makes no sense to use PC2-5300 / 667Mhz... unless they're less expensive." Just because it has PC2-4200 in it now doesn't mean it doesn't have a 667FSB. Dell shipped laptops with a 667fsb and 533Mhz memory. If it has the core 2 duo with the 667FSB then you'll want the PC2-5300. The D820 supports core 2 duo's with the 533 and 667 FSB it also supports PC2-4200 and PC2-5300.
http://support.dell.com/support/edocs/systems/latd820/en/ug/specs.htm#wp1057468
http://support.dell.com/support/edocs/systems/latd820/en/ug/specs.htm#wp1057468
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As a side note, if the PC2-5300 runs at lower speed you'll have to manually adjust the CAS latency to CL4, standard it would always stay at the value the SPD chips sets default, this case CL5.
Actually, SPD data is a table that shows the designed values for several speeds (all of the common speeds the memory supports). If 4 clocks at the lower speeds provides sufficient delay, the SPD would almost certainly report a timing of CL4.
You can see the SPD data your module reports on the SPD tab of CPU-Z => it will show it in columns with the values reported for each speed. http://www.cpuid.com/cpuz.php
You can see the SPD data your module reports on the SPD tab of CPU-Z => it will show it in columns with the values reported for each speed. http://www.cpuid.com/cpuz.php
Oh, sorry didn't know that, i'm learning every day. I tought the SPD would suggest one value not matter what speed.
Just to re-address the issue of whether it supports it... We have over 400 D820's that are Core 2 Duo's, but they are ALL limited to the 533MHz bus...
So folks need to look at what they have... in the case of these Dells, it totally depends on the D820's in question. Why companies don't change model #'s when the computers are different I will NEVER know...
So folks need to look at what they have... in the case of these Dells, it totally depends on the D820's in question. Why companies don't change model #'s when the computers are different I will NEVER know...