Newbie RAM Query.........

xirokx

xirokx

xirokx

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Joined
2 Oct 2004
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Hi,

Can someone kindly explain CAS please as I am interested in purchasing this RAM...

Corsair 2GB DDR Value Select PC3200 CAS3.0 Kit

I also see CAS 2.5 and so on and so forth...

Is this just marketing jargon or will it make a difference when overclocking....

Thanks in advance...

Cheers!!!!
 
hey thanks....

So if CAS 2 offers more performance compared to CAS 3 due to clock cycles etc...does this mean CAS offers more performance than CAS 2??

Just trying to be logical....

???????

Thanks in advance
 
lower cas timing = faster, but then again faster fsb = faster to. the problem is its usually one or the other as when the fsb is increased above what the ram is rated to run at, the timings need to be loosened (increased).
 
Is the fastest mem timings on a 1:1 divider?

I noticed I have the ability to change CAS, TRS etc etc in my bios when overclocking...

Ideally what should these be set to? Or am I trying to generalise it too much?

Alternatively does CAS, TRS etc make the RAM run even quicker if you set the RAM to a 1:1 divider? As you say you increase the RAM timings when you increase the FSB so I am just wondering how to tackle that?

Or does nobody bother changing the CAS, TRS etc settings when overclocking?
 
basically the ram is rated to run at a certain speed at certain timings. if you increase the speed at which it runs, the timings may need to be increased although the speed can usually be increased by quite a margin before the timings need to be loosened. when running 1:1 there will come a point where the fsb is simply too fast for the ram (say pc3200 ram is rated to run at ddr400(200mhz fsb)). if the fsb is increased to say 250mhz this is clearly too fast for the ram in question. therefore, either the timings can be slackened to allow the ram to continue to run at 250mhz (although it still may not) or a different divider can be chosen, say 166. this will make the ram run at 1.66x250 in this example which is equal to ddr415 (207mhz) which the ram is more likely to run at with its rated latencies. i would leave the timings at stock and overclock the system from there, lowering the divider whenever the ram becomes the weak link. hope this helps :)
 
Hey ladforce...

You have raised a lot of good points....

ATM I have increased the fsb on my machine from 200 to 235 and its stable...
without changing the RAM timings..

I then tried changing the RAM timings from 1:1 DDR 200 to 5:3 DDR 333 and then increasing the fsb to 240 but my machine was not stable...Thereafter I tried diff combinations DDR 266 4:3, DDR 400 2:1 but the system was still unstable.

Therefore I wondered whether changing CAS, TRS and others RAM settings in the BIOS would help me increase the FSB to 245 or even 245??

I am an overclocking n00b, I mainly followed diff guides to find the limit of the CPU, multi, htt and RAM but so far I have only got as far as changing the CPU and Multi which has enabled me to run my system stably at 235...As far as HTT and RAM are concerned I have not been that successful. Altho that said I did lower the HTT from 1000 to 800 but didnt see much of a diff so set it back to 1000 and with the RAM I just tried diff dividers as I am not that confident of what to do with the individual settings??? Someone told me I shouldnt bother with things such as CAS, TRS and other ram details when overclocking however they did mention it was important to set a divider...I have 4 x 256mb ram sticks of PC3200 which I am running on a 1:1 divider
its currently running at 195mhz instead of 200mhz?

If you can offer more advice with regards to the above I would be really grateful...

Thanks
 
if you use cpu-z it will tell you under the memory tab what speed your ram is running at. im not sure which way those dividers are working ie. not sure if its making the ram run faster than the fsb or slower as i dont have your board. on mine i have a 133,150,166,183 and 200 divider. im currently running an htt of 300, therefore, as my ram is rated to run at ddr500 (250mhz) i selected the 166 divider giving me 1.66x300 = 250mhz. If i try and select the 183 divider the system is not stable. this is just how i work out the divider i should use and it looks like your board has a different way of expressing the dividers. i would test a couple of them and see what they correspond to in terms of mhz to the ram. the ht multiplier should be left at 3x just so that doesnt cause any problems. the system may be unstable at 240 due to lack of volts to the cpu so i would increase the vcore by 0.05 volts just to give it a bit more juice. if this turns out to be stable then reduce it a bit more by say 0.025V. sorry if ive repeated anything from my previous post i forgot wht i wrote :) oh and also, as long as you keep the ram running at its rated speed through the use of dividers, the timings shouldnt need to be changed. if you want to tighten the timings up at all that should be the very last thing you do once you have the frequencies stable. also, make sure 1t command rate is disabled as your running 4 sticks of memory. the ht multiplier and cpu multiplier are two very different things, i only bring this up as you say you have changed the multiplier. the cpu multiplier should be left at stock.
 
when i decreased the multi I got a higher fsb and its all about getting the fsb to a higher and stable setting so I was told...

I use cpu z and my ram is running at 195mhz....

Everytime I changed the divider my system was unstable on prime etc...

However I was just wondering what else I could do to change the RAM which would help me increase the fsb....

Also change the vcore and its stable with decent temps early 40's which is not bad for a amd 64 3500 newcastle....

So as I ran out of ideas I gave up but your post inspired me again....I think I wont change anything now though becuz I am not confident it will do much...

I have tried the RAM on all diff multiplers...

Thanks mate
 
xirokx said:
when i decreased the multi I got a higher fsb and its all about getting the fsb to a higher and stable setting so I was told...

I use cpu z and my ram is running at 195mhz....

Everytime I changed the divider my system was unstable on prime etc...

However I was just wondering what else I could do to change the RAM which would help me increase the fsb....

Also change the vcore and its stable with decent temps early 40's which is not bad for a amd 64 3500 newcastle....

So as I ran out of ideas I gave up but your post inspired me again....I think I wont change anything now though becuz I am not confident it will do much...

I have tried the RAM on all diff multiplers...

Thanks mate
Click to expand...

the higher fsb was just offset by the cpu multi i would imagine, ie multi at 10 and fsb 200 = 2000mhz clock speed. or multi say at 5 with fsb at 400 = 2000. i think this is why.... hmm have you tried the ram at various vdimm settings betwen 2.5 and 2.8. some ram likes different voltage to other ram :) low 40s is fine for temp i reckon it can go a bit higher :) keep tweaking and upping the vcore till a max of about 1.475-1.5 but keep an eye on the temps. good luck :)
 
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but if the rams running at its rated speed and at rated timings, then its no different that running it at stock. or very little difference anyway and this component wont be stressed much above stock levels. if anything it will be the memory controller on the cpu failing at higher speeds or just the chip cant go any faster :p still the speed your running is not bad at all :)
 
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