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Learning things about oc, but have a question.

D

D4RK1C3

Gawd
Joined
Jan 24, 2005
Messages
866
i was wondering what the advantages and disadvatages there are to using the ram divider in an overclock. I think logically it is best to keep it at a 1:1, but is there a preformance hit by changing it. Thanks for your time and help.
 
I relatively new to overclocking. In fact I just had my first significant overclock with my AMD Athlon 64 3000+ from 1.8 GHz to 2.4 GHz. RAM is much more sensitive to a change in the FSB rate, keeping a 1:1 ratio will work, but you won't get the maxium overclock out of your cpu. Changing the ratio for the RAM will let the RAM stay in a range it tolerates while getting the maxium overclock out of your CPU. There is no performance hit I've noticed, if there is it is completely overshadowed by the extra performance you can pump out of your CPU.
 
i understand that the max oc will not be gained

but what im debating is what processor to buy based on the multiplier.
My thought is that a processor with a 12x multiplier and ram that can go stable up to 250mhz could logicaly (probably not in reality) reach 3.0ghz with a 1:1 ratio.

so i simply want to know if their is a preformance loss by using the ram divider
 
hmm this gets real technical real fast but here is the basic idea grossly oversimplified.

AMD cpu do not have extreamly deep "pipelines" where instructions to be executed can pile up (not exactly the same as cache but kinda like it, as I said, its complicated). and so a quick access to memory makes the processor "happy". When the processor clock and the memory clock are not in "synch" this can cause wait states where the cpu has to wait on slower memory to feed it. Benchmarks have shown that in most (notice the most, not all) general cases reducing the memory speed (kicking in a memory speed divider other than 1 to 1) so you can crank up the CPU clock via the FSB speed without your memory crapping out, makes the sytem slower because of the lower memory bandwidth and the added wait states needed to do proper data handoff between the cpu and the memory.


With 1 to 1 its much simpler for the cpu to "talk" to the memory and get what it needs when it needs it.


Intel cpus have deep (compared to AMD) pipelines and are not affected as much by this. So the general rule of thumb is AMD 1:1, Intel, play and bench and see what is best.


A google of memory divider will give you enough reading for the entire weekend and a blinding headache.


Ta.
 
thank you for you insight. this is what i was rolling over in my head, but was unsure. Thank you again.
 
though, on K8 based amd's (athlon64 and it's varients), the ram is never really "1:1", as the memory controller is on the cpu, running at cpu speed. the ram speed is derived from a integer divider ranging from 5 to 50, so technically the highest ratio you can get it 1:5
 
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