How relevant is the latency of DDR Ram? I know CL2.5 is better than CL3, but will the difference in performance justify

the extra cost?

Paul Heyden, Perth, WA

First, foremost and utterly important issue when choosing the RAM modules for your PC is getting a reputable brand rather than cutting costs by purchasing cheap, unbranded ‘generic’ modules.

Quite simply, the use of a reputable brand of RAM increases your chances of stability and compatibility. You should also always try to ensure that you use modules of the same make and model number together in your system, for the same reason. ‘Mix and match’ increases your chances of stability issues!

The RAM’s ‘latency’ is the next most important issue to consider.

The CAS Latency of your RAM is basically the amount of time your RAM sits ‘waiting’ for an instruction from the processor, and has an impact on overall system performance. Imagine a pair of identical high powered racing cars, sitting at the start line. If the driver of one has a longer reaction time to get the accelerator pedal pressed down, that car is going to be second to the finish line! A difference in your RAM’s CAS latency has a similar effect, and there are a hell of a lot of ‘Stop/starts’ involved in the way your computer functions!

In terms of overall system performance, however, the CAS latency of the RAM is only one of many, many factors contributing to performance, and the difference between low latency and high latency RAM might only mean a performance difference in the low single-digit percentages. Have a read of the article “CAS Latency: What is it and how does it impact performance?” for a more complete overview of the issue.

If that low-latency RAM is a significant increase in expense compared to the higher latency alternative, Paul, then under normal circumstances I’d suggest that the extra expense isn’t warranted. If you can obtain it for only a few dollars more, then why not go for it?

There is only one circumstance, really, where I’d suggest that the use of low-latency RAM really does make an important difference. If you've a read of the results of the testing done by on-line site Tom’s Hardware in the article “Ups and Downs: Memory Timings put to the Test” you’ll see that those people using high performance Pentium 4 processors for purposes such as games or video editing might just get more benefit from the improved RAM timings than anyone else. And even then, the improvement may not warrant the expense.

Yes, low latency RAM is better, but NO, I don’t believe that’s enough reason to spend a lot more money. To gain the extra benefit it might provide you’d have to start tuning and tweaking that system to the MAX! Its benefits are mainly for overclockers and those people in pursuit of the highest benchmark results they can get. For most of us, it’s overkill! Brand name and quality is all important, and if it’s those nice looking little dinky heat spreaders on the RAM which attract you, then hey - you can buy those separately and put them on your RAM modules anyway! You can even get ones which have wonderful little flashing LED lights in them like this set from Themaltake!

Cheers,

Terry O'Shanassy