Ram latency

[joeshmofro]

I am in the market to buy some new ram and I was wondering how much the low latency effects the speed. What does the low latency do?

[OS-Wiz]

Latency expresses a memory stick's delay in providing data to the CPU as a number, like CAS3, or 2.5 (DDR memory only), and 2.0. Obviously, the lower the number the better and the number is in clock cycles. Thus, to answer your question, CAS2 memory is 1/3 faster than CAS3.

[WildWeasel]

sorry if this is corny...but it sounds okay in my head...

The memory's rated speed (say, DDR400 or PC3200) reflects the maximum rate at which it can transfer data. The various latencies tell you how many clock cycles you must wait before the memory begins transferring data at it's specified rate.

If your current computer is a pre-built from dell/gateway/whatever, then it's probably running on really crappy timings. As such, you should just buy quality RAM (i'd recommend Crucial) without regard to it's rated latencies.

If this is for a system that you've built, with a BIOS that allows you to manipulate memory timings, then as far as the importance of low timings, the best thing you can do is test it out yourself. Many people claim that you should run the highest FSB possible with relaxed timings, and many say that you should settle for the highest FSB you can get with very tight timings...results will vary.
hope this helped...

[OS-Wiz]

The concensus opinion you'll notice as you browse various tuning articles is that you should first find your maximum FSB with the lowest latency memory timings. Then relax the memory timing a little, up the FSB and see if things improve.

Edit: I should have added that the above assumes memory in sync with CPU. When you throw dividers into the mix, it gets a little more complicated.

[joeshmofro]

Thanks that is helpful. I have one more question though. I you could recomend a brand of ddr what would it be. I have corsair ddt400 xtreme xms mem right now but I only have 256mb of it and I want to buy a 512 stick of something. I have no experience with other brands besides corsait. What are you thoughts?

[OS-Wiz]

Originally posted by joeshmofro
Thanks that is helpful. I have one more question though. I you could recomend a brand of ddr what would it be. I have corsair ddt400 xtreme xms mem right now but I only have 256mb of it and I want to buy a 512 stick of something. I have no experience with other brands besides corsait. What are you thoughts?

We need your system specs to help any further. Please add them to your sig. Click User CP > Edit Profile

[joeshmofro]

sorry I forgot to give them to you. I have the sis 648 chipset it sais it supports up to ddr400, but I dont know if anything faster would work. The rest of my specs are down at the bottom of the page.

[OS-Wiz]

Originally posted by joeshmofro
sorry I forgot to give them to you. I have the sis 648 chipset it sais it supports up to ddr400, but I dont know if anything faster would work. The rest of my specs are down at the bottom of the page.

Unless you normally runs apps that pacman memory, I'd just get another 256mb stick of the Corsair (512mb is usually enough for most users). If you want to go bigger, you'll have to check your mobo book again to see if it can handle the architecture of the stick you choose.