Question on overclocking.

[TooNice]

It used to be that you needed to keep the RAM and FSB at 1:1 ratio.

But nowadays, it seems that is no longer a requirement, with ratios and all.

However, is there any difference in performance to use a high FSB with the memory locked at 200?

I can understand that 250 x 10.0 would provide some performance advantage over 200 x 12.5 provided that the ram in the former runs at 250Mhz, and the ratio is set to 1:1.
But would the same be true if the memory is locked at 200Mhz on both case? And what sort of performance increase are we looking at? 1%, 2% or something more?

[Dark Horse]

Because Athlon 64's have the memory controller on the processor rather than the motherboard they have shedloads of memory bandwidth. Memory overclocking does increase this but in the majority of games (save Quake 3 and 4) there is very little difference, at most <5% from running your memory at 300 1:1 to 300 2:3.

More and more these days it is worth just getting value ram and spending the difference on a better graphics card as this will give you a far bigger performance increase.

[Rack]

The other thing that has been fairly well proven with the A64's is that timings, in particular command rate, make more of a difference to performance than raw clock speed. By going from 2T to 1T @ 200MHz you will as much a performance increase as you will by getting some very high speed dimms and going from 200Mhz to 250.

[b0redom]

I was pretty sure it was the other way around. 2T->1T doesn't make that much difference 200Mhz->250Mhz makes a stack (if we're talking about the FSB/HTT)

[Butcher]

The large cache on 64s helps as well - the larger the cache the less often you hit memory.

[TooNice]

So really, there is no real (significant) benefit from upgrading from one motherboard to another if overclocking is the only thing in mind is it? Especially if you dont have premium ram to go 1:1

Let's say on one motherboard you can only get 200 FSB and on another you can hit 300. The CPU roughly maxes at 2.4Ghz. So you can do 200x12 at 1:1 and 300x8 at 2:3. Would the performance be within 5% of each other?

[sawyen]

I would just stick with 12x200.. 300x8 would just b extra stress for ur chip..

Unless u bench, yea.. they are all within 3-5%..

[TooNice]

Interesting. How would a higher FSB and lower multiplier be extra stress?

I would've thought that the temp etc. would be constant since the CPU is operating at the same speed... or not?

[piranha]

1T performance over 2T is demonstrated more at higher fsb; dividers make little difference generally on A64 systems.

[toolsong]

All the evidence you need is here
http://www.dfi-street.com/forum/showthread.php?t=40178

[atmadden]

It is much more important to run at tight timings and low latencies but I will test theory as I have some ram that will run at 280mhz at 2.5 3 3 7 and at 200mhz 2225. Will post back later.

[Agent]

Interesting. How would a higher FSB and lower multiplier be extra stress?

I would've thought that the temp etc. would be constant since the CPU is operating at the same speed... or not?

The mem controler on the CPU would have to be workling a lot more to deal with 300mhz over 200mhz worth of data. Remember, its [the controler] on the CPU itself now

[TooNice]

I feel enlightened after reading toolsong's link and Agent's post above.

I guess I don't -have- to switch my Asus A8N-Premium for a AR32-MVP Deluxe, especially considering that I don't need Crossfire.

(So far, I've yet to work out how adding a 2nd graphic cards later on as the GFX card get cheaper can be better value for money than just selling the current card and upgrade to a new one a generation down the line).

[Butcher]

(So far, I've yet to work out how adding a 2nd graphic cards later on as the GFX card get cheaper can be better value for money than just selling the current card and upgrade to a new one a generation down the line).

Heh, it's not. The only reason to go dual card is if you want two top-end cards. Value for money doesn't enter into it (despite what the vendors want you to think)].