FSP:DRAM ratio 1:1????

[wun911]

Is a 1:1 ratio the optimal overclock?

ie will I still see some prefromance gains when its not in the 1:1 ratio?

I can push my FSB to 985
but my RAM doesnt go past 820...

 

[The_Prophecy]

A 1:1 FSB:RAM ratio is not an overclock. It simply means that the FSB and RAM frequencies match exactly.

A Pentium 4 630 CPU uses an FSB of 200Mhz. Many systems that can take the 630, use DDR400 ram, which runs at a frequency of 200Mhz as well. This gives a 1:1 ratio. Similarly, a Core 2 Duo E6300 has a stock FSB of 266Mhz. Almost all motherboards that can accept these chips need DDR2 ram. DDR2-533 runs at a stock frequency of 266Mhz. This also gives a 1:1 ratio.

In both cases, neither the FSB of the CPU, nor the frequency of the RAM has been overclocked above their respective stock values.

Generally when one overclocks their system, the desirable result is still a 1:1 ratio. The performance gains achieved by tweaking your system to gain the 1:1 ratio are not really gains... what you're actually doing by getting the 1:1 ratio, is allowing your system to run as efficiently as possible. When the FSB and RAM are not running synchronously, CPU and RAM cycles are wasted (no data is passed between the RAM and CPU). When you adjust the frequencies to match, you're allowing the system to do more in the same amount of time.

 

[wun911]

So wait!!!! Is asynchronos overclocking a waste of time ie you will only see preformance gains if your memory keeps up to your OCed CPU????

In my bios FSB is displayd as 800??? not 200 or 266????
And my CPU muliplier is 18

so where does my 3.6Ghz come into the equation???

 

[Guest]

800 is because Intel use quad pumped FSB, so 200mhz sending 4 times the data is like a 800mhz.

200(fsb) X 18(multiplier) = 3.6ghz(cpu speed).

The ram use DDR so it send twice the data every cycle so DDR400 ram is going at 200mhz but it's like 400mhz. When put in dual channel you get a perfect match for your processor at 800.

While ocing with P4, keep 1:1, that 3.6 probably wont go to far on air since it's already pretty much at the limit of the architecture.

The new Core 2 duo and the A64/X2 perform well with 4:5 memory divider, it allows you to run the ram faster then the frontside bus.

200 mhz * 5 /4 = 250mhz, the ram runs use Double Data rate so your ram will be running like if it was at 500mhz, with dual Channel you get the equivalent of 'normal' ram operating at 1000mhz.

That allow you to push the ram further without OCing the CPU. That being said you need ram that will support those higher frequencies.

 

[The_Prophecy]

I was using the real frequencies, not the effective frequencies. (I know you knew that labbbby, I was saying that for the OP's benefit)

The new Core 2 duo and the A64/X2 perform well with 4:5 memory divider, it allows you to run the ram faster then the frontside bus.

There's more benefit to running the 2 in sync, rather than trying to raise the clocks on both as much as possible. Think efficiency, not just pure horsepower.

 

[Guest]

Well I never own a A64 so I don't know for sure but I though the A64 ODMC handle the async really well. And due to the fact that there's no 'real' FSB on the K8 I thought it make sens

Anyway I am a big 'fan' of 1:1 operation and almost always used it. Probably will stay like that unless I get a true Async board like the Rd600.
I usually don't run hundreds of bandwidth benchies and just go with 1:1 =)

 

[The_Prophecy]

I don't run hundred's of benchmarks either..... it just makes sense logically to run at a 1:1 ratio.

 

[little_scrapper]

So will you see a benifit from running teh memory way faster then the CPU. Bump hte memory ration way up or however its done. I heard that you can do that on the 680i. Do you actually see a gain? For exaple: lets say i have a E6400 and DDR2 1000 memory. if I leave the CPU at stock and crank up the memory to 1100 or soo will it give better performance or will all that speed be wasted waiting for them to sync up again? Or even if I OC the CPU but the memory can OC better, will I see benifit from running the mem maxed out.

 

[The_Prophecy]

Running the RAM at a higher frequency than the CPU's front side bus may seem like a good idea because of the higher ram bandwidth, but that benefit is offset by the cycles that are wasted from not having that 1:1 ratio.

You probably won't see any more gain from a higher frequency and an asynchronous ratio, than from a lower frequency and a synchronous ratio. Run at the lower frequency with the 2 sync'ed, because the higher the frequency you run something at, generally the higher the voltage needs to be, therefore.... the shorter the product life.

 

[little_scrapper]

ok TY

 

[Mondoman]

Running the RAM at a higher frequency than the CPU's front side bus may seem like a good idea because of the higher ram bandwidth, but that benefit is offset by the cycles that are wasted from not having that 1:1 ratio.

Sometimes this is true, sometimes it is not true. It depends on (1) the MB design and (2) how much faster than a 1:1 ratio the RAM is run. You need to do real-world testing to find out what is the case in your situation.

Testing that I've seen on a C2D system indicated that going to DDR2-667 from the synchronous DDR2-533 didn't help under latencies slower than CL3. Going to DDR2-800 did help even with CL5 latency. YMMV.

 

[wun911]

In BIOS my CPU is set to like 990 makin my CPU from 3.6 to 4.4...

But my ram remains the sam ie 800....


I dont "feel" like my PC is going any faster,

I cant oc the ram past 802 or it crashes....

I think I have just reached my limit....