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Memory latency and FSB clarification needed

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Wangster

Official O/C Santa Ferret
Joined
Apr 19, 2002
Location
Austin
Is it better to have a more conservative FSB running using the most aggressive memory timings or is it better to have the highest possible FSB (stable) using more conservative memory timings?

Please help,

Wangster
 
This is a shot in the dark but I would say FSB is more important... why else would so many overclockers cut their throats just for FSB hahaha... even if they are running at CAS3 7,9...
 
It seems like it's no big difference in sd ram, but matters more in ddr sd ram. I belive a 176mhz cas 3 module would lose in real performance to a 166 cas 2 module. But that's just my 0,02$ ;)

elysium
 
I have PC133 256MB CAS3 SDRAM, that runs at BIOS setting CAS2, but the difference between CAS2 and 3 at 133 is only 1% better with CAS2. (And the ram can do 149FSB CAS3)
Is this just because my ram can't do CAS2 at 133 but pretends it can, or is this normal for SDRAM with CAS2 and 3 at 133????

The ram is so generic there even I don't recognise the producer (which isn't saying much, just that I know a fair few of the producers).
 
Strokeside,

Definetly, the difference in *memory access performance*, comparing cas 3 with cas 2 at the same speed (FSB) should be bigger (in fact, around 15%). BUT, a computer is the sum of its components, and rel life or generic benchmarks do not test ONLY memory speed... so in real life and for this scenario, the difference may vary from 0 to 15%, all other system specs equal.

If you are measuring with sisoft's Sandra memory benchmark, and getting only 1% difference, then you are right, your BIOS is probably setting CAS3 even if you say you want CAS2... (check the SPD settings).

Regarding this thread's initial question, I agree in general FSB is more important than CAS setting. By this I mean, it is usually better to drive a locked system to it's FSB limit at the more relaxed memory timings than stop overclocking just because you do not want to concede a bit on the mem timings.. as with everything, there CAN be exceptions.

Regards
FTC
 
Iv often wondered this myself, and this thread prompted me to find out. I found that changing CAS latency from 2 to 2.5 is about equal to a 10mhz change in FSB speed. I got nearly the same results in sandra running FSB 160 @ cas2 and running FSB 170 @ cas 2.5. However, i wasnt able to run at 170 fsb @CAS 2, so its a trade off, if you cant unlock your processor, or dont want to, go with slow timings and high speeds.
 
I asked this question a long while back and I was wondering if anyone else have come up with new opinions on this subject.
 
Got tired of hearing opinions and did some testing on my system a little while back. Results are here, (link deleted). Select the "Memory Settings and Their Effect on Overclocking" from the table of content.

For my system, 5% max change in performance from most aggressive to least. Thus 190Mhz FSB with aggressive timings was equal to 200Mhz FSB with least aggressive timings.
 
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Basically, don't sacrifice 50MHz from your RAM just so you can lower your CAS by .5. It's totally pointless. Unless you have an AMD system, then only run your ram as fast as your FSB. For P4's crank it up and get evey MHz you can out of that stick :D
 
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