Ram CAS confusion!

[mathewdbarlow]

Can anyone explain exactly what the CAS values mean in regards to Ram, and what I should look for to maximise the performance of my gaming rig? I have Corsair value ram 667mhz and the values are 5 5 5 15, I notice that other ram has different values. Any explaination appreciated.

Thanks in advance!

[kalniel]

It's basically a collection of measurements of the time taken for various parts of the operation of memory, ie latency.

All you need to look for really is 'lower is better', but at the end of the day for DDR2 the timing is not as important as it used to be for DDR1.

Slightly old explaination of the values here: http://www.dewassoc.com/performance/...as_latency.htm

more recent can be found with google I'm sure

[mathewdbarlow]

Thanks for that Kalniel. just a couple more things.

I have noticed an option to change the values in the bios, presumably this is one way to overclock ram (I am no overclocking expert). Is it worth tinkering with these settings or is it best to use an overclocking tool in windows to control the ram speed?

Also, does altering these values pose any risk of damaging any components or affect stability or even affect warranty etc??

Thanks

[kalniel]

It's not quite overclocking to change these values - you are basically waiting less time for an answer before proceeding with the next stage in the memory.

As such you won't likely damage any components by lowering timings, but if the memory can't get the operation finished before the answer is requested then you get a memory error, which can cause system instability. However all you need to do is thoroughly test your memory for errors to determine if it's stable at your selected speeds - memtest86 is a great tool for this.

I prefer using the BIOS to change these settings, but some people have had great success using windows tools to do it, so I don't think it really matters.

Whether it's worth it or not is another matter - as mentioned it doesn't really affect real world speed except in very memory intensive tasks - usually only benchmarks! However if your ram is 100% error free at tighter timings then there's no reason not to.

If you were interested in increasing performance, then increasing the speed of DDR2 RAM has greater effect - note that you might have to actually loosen(raise) timings to enable RAM to run error free at higher speeds, and running at higher speeds *does* usually void warrenty.

[mathewdbarlow]

Excellent, thanks for your help!

[this_is_gav]

Just for reference, with an Intel-based system, lower timings values generally doesn't make much difference to performance at all. You certainly won't notice any difference without benchmarking, and even then there's very limited benefits.

Lower timings can make quite a difference with Athlon64s with their onboard memory controllers.

[Clunk]

Tighter timings at higher bandwidth do make a noticable difference.