CAS Latencies

[mike_w]

This has come a few times on the forum before, but I just want to make it crystal clear in my mind: just how important is CAS?

What I mean is not how different sticks will overclock, but what the performance difference is at the same speeds, except for the CAS. For example, is there any significant difference between CAS 2 and CAS 3 at PC3200 speeds? Would it be noticible in things like games, or is it something like 2fps difference?

Thanks

Mike

[Firelord]

Which setup is the question!

if its P4 then it doesn't really make to much difference. P4s bandwidth doesn't really change with loose or tight timings.

AMD Athlon XP on the other hand is whole nother kettle of fish. CAS latencey is very important and CAS2 is optiumum for them nForce 2 is best at 2-11-2-2. CAS2.5 and above does make performance suffer. Tight timings is the way to go for XP systems.

A64 on the otherhand is a little bit of a mix... I found CAS2 makes a lot of difference but the other timings not so much. CAS2.5 still performs well and CAS3 is well CAS3 and really an Intel sorta timing...

[mike_w]

AMD Athlon XP on the other hand is whole nother kettle of fish. CAS latencey is very important and CAS2 is optiumum for them nForce 2 is best at 2-11-2-2. CAS2.5 and above does make performance suffer. Tight timings is the way to go for XP systems.

Just how much difference will it make though? Although it may make some difference, is it worth buying CAS 2 RAM for, let's say, £50 more than some CAS 3 RAM? Will it be noticable in things like games rather than benchmarks?

Thanks for the reply

Mike

[yamangman]

If your talking gaming terms, it'll barely make a scratch, my RAM is rated at CAS 2.0 at 100MHz and CAS 2.5 at 200MHz. The performance is exactly the same for both, if you can get some RAM that will do CAS 2.0 (as opposed to 2.5) at 200MHz (DDR 400) there is a slight performance increase, but you'll barely notice it in games.

[mike_w]

If your talking gaming terms, it'll barely make a scratch, my RAM is rated at CAS 2.0 at 100MHz and CAS 2.5 at 200MHz. The performance is exactly the same for both, if you can get some RAM that will do CAS 2.0 (as opposed to 2.5) at 200MHz (DDR 400) there is a slight performance increase, but you'll barely notice it in games.

What about performance loss from CAS 3 RAM compared to CAS 2.5?

[Donny John]

Don't bother spending much more cash m8, I had 2 x256Mb Twinmos @ 2.5/200Mhz Dual (400) spent wanda on Mushkin CAS 2 same speed no noticable difference. Maybe benched 3-4% better, pushing to 220Mhz is good though, same timings CAS2 etc. 8-10% increase is noticable alright

See how far the Twinmos will go, try more volts

Set the RAS to 11 if u got dual as well okay

[Firelord]

If your talking gaming terms, it'll barely make a scratch, my RAM is rated at CAS 2.0 at 100MHz and CAS 2.5 at 200MHz. The performance is exactly the same for both, if you can get some RAM that will do CAS 2.0 (as opposed to 2.5) at 200MHz (DDR 400) there is a slight performance increase, but you'll barely notice it in games.

Exactly CAS2 @ 100FSB is the same as CAS2.5 @ 200. Call me stupid but surely then you'd want a CAS2 ram module if thats the difference in performance.

Donny John TwinMOS is good stuff and stick enough volts through her and they fly but do the same to the mushie with lower volts and it will chew it up and spit it out!

if you are overclocking or doing RAM intensive tasks ie Photoshop, CAD and video encoding; grab the best RAM you can afford that'll do CAS2.

Otherwise grab soemthing like Samsung or TwinMOS that does CAS2 with some volts and ocs as well as they are very good memory.

[Donny John]

Donny John TwinMOS is good stuff and stick enough volts through her and they fly but do the same to the mushie with lower volts and it will chew it up and spit it out!

What does that mean? My Mushkin is fine at 220Mhz CAS 2 2.8v!

If u read his sig he already has Twinmos w/ Winbond Chips, he's asking if it's worth spending a lot more money on memory that will go CAS 2 at 200Mhz.

I'm saying no! Just push the Twinmos as high as it will go basically, the slight performance increase I got prolly wasn't worth the extra cash when I switched to Mushkin.

[madwelshboy]

Hi guys,

I think the main point here is whether cas latency makes a noticeable different ie in games.
One of the main points to consider is the poeple that are buying cas 2 memory also have other high quality components (A64 cpu, x800 gpu etc etc), so cas 2.5 or 3 would drag (slightly) their system down, whereas cas 2 is better for them.

Mike_W: Looking at your system specs, I would say that cas 2 memory wouldn't make much of a difference to you from cas 2.5 as your "bottle neck" (in games atleast) is prob your graph card (or even hard drive - as with 512mb of mem I'm guessing you have page filing on?).
I would save your money, your system looks pretty level par atm :-)

[TiG]

I'd also not recommend ram settings of 2-11-2-2 because i'd definitely argue that its not ideal of system performance - SOME and i do mean a limited number of applications benefit from the settings being set to this speed, i'm talking 3DMark - the reason for this is it ties in with a commonly used command and therefore ties into the base level of processor pipelines (Much better for AMD than Intel - AMD pipeline of 14 cycles and Intel P4's at 21 cycles AFAIK)

All we are talking about with CAS cycles is how many cycles it takes for the memory to do operations that the processor is waiting for. The lower the better generally but we are not talking huge amounts of performance increase. Simply because in normal operation everything is fine.

The way the memory market is going at the moment is definitely with MHZ increase at the cost of Cas Latency and Mhz is more important from all the reviews i've seen. But i'd always prefer to have my memory in Sync with my processors if i could.

TiG

[mike_w]

If u read his sig he already has Twinmos w/ Winbond Chips, he's asking if it's worth spending a lot more money on memory that will go CAS 2 at 200Mhz.

I'm saying no! Just push the Twinmos as high as it will go basically, the slight performance increase I got prolly wasn't worth the extra cash when I switched to Mushkin.

The problem I have is that I like the RAM I have now, its just that I wanted another 512 stick. Unfortunately, Komplett don't seem to do them anymore, and I can't find them anywhere else, and I'd prefer to have all the RAM as the same in my system.

Thanks for the replies everyone, I think I'll just stay on the lookout for anymore cheap, but still decent, CAS2.5 RAM since its not really urgent.