Mem dividers in A64 decrease performance?

bLack0ut · Nov 29, 2005

Well, course I read the stickys, but while perusing through the forums, I noticed ppl still say "Well I can hit 280, but that would mean doing <insert divider other than 1:1> so I dropped it down to 250". Is there any validity in that statement or is that just ignorance?

electrorcamd · Nov 29, 2005

There is some performance drop from the reduced bandwidth, but it is usually not too noticeable, unless it is a large change. There technically is not a 1:1 divider on the A64, so basically the only change in performance is from the bandwidth change.
On the nForce2/ AXP platform however, running the memory at a divider of other than 1:1 would result in a fairly noticeable loss, with much slower latencies.

rseven · Nov 29, 2005

Ignorance! The old habits we all learned running AXP's are just very ingrained. We need a new commandment,

"Thou shalt never sacrifice a higher CPU clock for higher ram speed on an A64!"

Sorry, I don't have a really big tablet in my medicine cabinet. I'll have to settle for a Tums. I think that burning was heartburn!

bLack0ut · Nov 29, 2005

Huh, follow the yellow or the white stars' advice. Yellow? White? Oooo the white stars so shiny! THE GOGGLES, THEY DO NOTHING!

Rseven, got any benchies/rl times, etc etc. I need proof

same goes for electror

(cf)eclipse · Nov 29, 2005

think of it this way:

the memory controller runs at cpu speed. even at "1:1", the memory divider is the cpu multiplier... or rounded up to the nearest integer if you're using a 1/2 multi.
thus, when you change the memory divider, you're just changing from one divider to another

the overall effect on performance is quite small unless you're counting seconds, points and fps. it's not noticable otherwise

electrorcamd · Nov 29, 2005

bLack0ut said:
Huh, follow the yellow or the white stars' advice. Yellow? White? Oooo the white stars so shiny! THE GOGGLES, THEY DO NOTHING!

Rseven, got any benchies/rl times, etc etc. I need proof

same goes for electror

Rseven just said what I said in a slightly different, shorter way.
There is a difference from the change in bandwidth, but it is not a noticeable difference.

rseven · Nov 29, 2005

bLack0ut said:
Huh, follow the yellow or the white stars' advice. Yellow? White? Oooo the white stars so shiny! THE GOGGLES, THEY DO NOTHING!

Rseven, got any benchies/rl times, etc etc. I need proof

same goes for electror

LOL!
Hey, I'm from Joisey and our State Motto is, "You want some a dis!"

Electrorcamd, you are correct about some lost bandwidth if you run the CPU at the same speed, but if you slow your CPU down from 280 to 250 to run 1:1 you'll lose bandwidth.

Mem dividers in A64 decrease performance?

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