Will running my ram at CAS2 be that much faster than CAS 2.5 on an athlon?

[aka1nas]

Hi all,
I am trying to wring more performance out of the limited overclockability of my MSI K7d. My FSB is limited to 150 max and I can't go above 12.5x multi. I can run at 150Mhz FSB at CAS 2.5 rock solid for a final clock of 1875Mhz. I managed to get my crucial PC2100 to do CAS2, but if I FSB OC then it gets prime errors(only on large FFT torture tests though.). So I guess the question is: Which is prefferable; 12.5x@133Mhz CAS2 or 12.5x@150MhzCAS2.5. I have heard that Athlons love low latency, but will it make a difference in real world performance enough to compensate for a lower FSB? If running at CAS 2 really does make a big difference, what kinds of program benefit the most?

More complete Specs:
MSI K7D -L BIOS 1.91
2 AthlonMP 1700+s @ 2000+@ 133FSB
2 CAS 2.5 Crucial PC2100(one is actually PC2700 cas2.5 running at 2100 speed)
GeforceFX 5900nu

 

[myocardia]

12.5x150. You're only giving up .5 on your CAS timings. Every little bit helps, but it isn't doing to make up for the clockspeed difference.

 

[sandorski]

Since you have everything already, bench it yourself.

 

[Richdog]

Originally posted by: sandorski
Since you have everything already, bench it yourself.

No that would be too easy.

 

[aka1nas]

Hehe, I guess a better question is which types of programs usually benefit from having lower latency RAM on an Athlon so I have an idea what to benchmark. I've been runnign sandra just to see if it made any difference, but something that isn't completely synthetic would be a bit more useful.

P.S. Think I may have gotten it prime stable at 140Mhz FSB cas 2. Its been going 8 hours without an error.

 

[Duvie]

Try running it on apps you will be running with this machine!!! Otherwsie it doesn't do you any good...You are trying to optimize your machine to your uses.....

using cas 2 or 2.5 at same speed was all I tested and big jumps were seen in superpi, 3dmark01, not so much in encoding programs I tested.....

 

[aka1nas]

Thanks Duvie, that was what I was looking for.

 

[Spike]

Kinda a noob question here... I bought a stick of that giel value pc3200 512mb ram with heatspreader from newegg. It runs at cas 2.5 and I was wondering if it is wise to change that or if I should wait till I get nicer ram (possibly a year away). I also run a athlon (2500+ @ 2.2ghz). Thanks

-spike

 

[myocardia]

Originally posted by: Duvie
Try running it on apps you will be running with this machine!!! Otherwsie it doesn't do you any good...You are trying to optimize your machine to your uses.....

using cas 2 or 2.5 at same speed was all I tested and big jumps were seen in superpi, 3dmark01, not so much in encoding programs I tested.....

Hey man, he said at the same speed.

Of course faster timings are better at the same speed! But, if you're gonna get 10mhz higher fsb, by only changing your CAS timing by .5, you'll get better results. Try it, and see if I'm right.

 

[DAPUNISHER]

Originally posted by: myocardia

Originally posted by: Duvie
Try running it on apps you will be running with this machine!!! Otherwsie it doesn't do you any good...You are trying to optimize your machine to your uses.....

using cas 2 or 2.5 at same speed was all I tested and big jumps were seen in superpi, 3dmark01, not so much in encoding programs I tested.....

Hey man, he said at the same speed.

Of course faster timings are better at the same speed! But, if you're gonna get 10mhz higher fsb, by only changing your CAS timing by .5, you'll get better results. Try it, and see if I'm right.

With my nF2 setup I agree with you completely, 5-10mhz was > than cas.5 better. P4c is a different beast though from what I've read. Looks like 3200DDR@2-2-2-6 is faster than 3700DDR@3-4-4-8 in many situations as long as it means you can push your clockspeed higher in exchange for faster ram speed with slower timings IIRC.

 

[aka1nas]

Well if my rig hasn't caught on fire when I get home tonight I may just leave it at 140FSB@cas2. I don't have PCI or AGP lock or dividers past 133 on this rig, so im already a bit out of spec. best not to push it too much more.

 

[myocardia]

Actually, if you don't have a pci lock, I would leave it at 138fsb@CAS2. Most hard-drives start corrupting data at anything faster than 138, if you don't have a lock. Wait, what was I talking about? You've already got some PC2700, why not take out the 2100, and run a 166fsb? You would then be running your pci at the 33mhz default, because you made it to the next divider. That's assuming, of course, that your board will "support" a 333fsb processor. If it will, PC2700 ram is cheap, man.

 

[aka1nas]

Its a MPX board, so it only supports PC2100, though the MSI k7D synchs the RAM with the FSB always. I can only go to 150Mhz FSB from the BIOS, which is seemingly ok at CAS2.5. That runs my PCI and AGP quite a ways out of spec, though the extra bandwith might be nice as having two CPUs share a single channel of memory tends to make this chipset somewhat badnwith starved. Also, it would be ncie to overclock the video card too, and I am unsure if the 5900s handle an overclocked FSB ok.

 

[robcy]

150fsb at CAS 2.5 is betten than 140fsb at CAS 2. Just my 2 cents

 

[myocardia]

Well, if it only supports a 133fsb, I wouldn't run it any higher than a 138fsb, unless you like "wiping" your hard-drive every few months, and reloading everything. Besides, 2mhz fsb is nothing at all to get excited about. Those of us with a nForce2 motherboard usually go up by either 5 or 10mhz at a time, when seeing how high we can push our fsb's. Why don't you try running the Prime95 blended torture test @140fsb, and see what happens?

 

[aka1nas]

It's passing all the torture tests at 140Mhz FSB at CAS2 currently. I think that may be prefferable as I don't have AGP or PCI locks and/or dividers like an NF2 board would so at 140Mhz my AGP is 70Mhz and my PCI is 35Mhz. That probably isn't too bad, but 75 and 37.5 may be a little high to run them at. In particular I am unsure whether my RAID card and my Gfx5900nu handle overclocked busses well. I think I will eventually have to hardmod the mutliplier for 2400+@133FSB and see if they hit anything higher from there.

 

[aka1nas]

One more possibly noobish question: if my CPUs are stable at 1875Mhz at 150FSB, would it be reasonable to assume that they would handle around that clockspeed with a lower FSB and a higher multiplier? I have had one of the procs running at 2400+@166FSB in a single proc board before and they both currently hit what would be considered the equivalent of 2300+@150FSB. I was thinking of hard moddiing the multiplier to make them 2400+ chips and maybe just running at 133FSB with the most aggressive timings I can get the RAM to do. Does this sound reasonable?