What are the "CPU FSB/DRAM Ratio" settings on AN7?

[computer]

Can anyone tell me please exactly what the settings mean under the BIOS area "CPU FSB/DRAM Ratio" on an AN7? The manual of course chose to leave this information OUT! :disgust: I have it set to "auto" but I'm sure that's probably not optimal and the FSB and or memory (TWINX512-3200LL) may be underclocked at that setting.
Thanks.

 

[Fern]

Well I don't use that mobo, but I do have it's older brother, the NF7.

The cpu fsb/dram ratio setting will determine the FSB your ram runs at. I use 1:1 or similar (ex. 5:5). This ensures that your cpu and ram are running in synch (same FSB speed), which is better for performance on an AMD system

The *auto* setting is likely the correct setting. However if you have, say, a 333 mhz cpu and DDR 400 (pc3200) ram, IIRC it'll run your ram at 200/400 FSB and your cpu at 166/333 FSB. That w/b asynch timings and not really recommended for AMD.

Does that help?

Fern

 

[computer]

Originally posted by: Fern
Well I don't use that mobo, but I do have it's older brother, the NF7.

The cpu fsb/dram ratio setting will determine the FSB your ram runs at. I use 1:1 or similar (ex. 5:5). This ensures that your cpu and ram are running in synch (same FSB speed), which is better for performance on an AMD system

The *auto* setting is likely the correct setting. However if you have, say, a 333 mhz cpu and DDR 400 (pc3200) ram, IIRC it'll run your ram at 200/400 FSB and your cpu at 166/333 FSB. That w/b asynch timings and not really recommended for AMD.

Does that help?

Fern

Thanks for the reply. I knew about that 1:1 ratio from a P4C800xxx mobo, but it's confusing on the AN7 since they have several apparently 1/1 settings; 3/3, 4/4, 5/5, and 6/6. IF they are all 1:1 (and I know they are mathematically), then why all the different 1:1 settings? They have got to differ some way. P4C800 was just as confusing since 1:1 on it is "DDR400" in the BIOS, regardless of CPU used!

CPU is a 3200+ Barton and memory is PC3200 Corsair TWINX512-3200LL 2 x 256mb.

 

[Fern]

"Thanks for the reply. I knew about that 1:1 ratio from a P4C800xxx mobo, but it's confusing on the AN7 since they have several apparently 1/1 settings; 3/3, 4/4, 5/5, and 6/6. IF they are all 1:1 (and I know they are mathematically), then why all the different 1:1 settings? They have got to differ some way. P4C800 was just as confusing since 1:1 on it is "DDR400" in the BIOS, regardless of CPU used!"

CPU is a 3200+ Barton and memory is PC3200 Corsair TWINX512-3200LL 2 x 256mb.

Yeah, the NF7's have the full range as well, all different ways to express "1:1". I researched it back when I got my board. Never found any kind of *technical* explaination (not that I would prolly understand it).

But in OCing some report better results with the 5:5 or 6:6 variants, Why? I've never heard an explaination given.

Since your cpu and ram both run stock at 200/400 FSB you should be OK running at *auto*. I checked my BIOS last night and found that mine is set to *auto* as well. I must have failed to reset 5:5 or 6:6 (whichever I had in there at others' suggestions) the last time I cleared the cmos-about 3 weeks ago. But I left it there cuz it's running just fine. In fact I had the FSB up to 220/440 last week, so *auto* works fine in our case.

That's odd that 1:1 on your previous board set the cpu and ram to different FSB speeds?

Fern

 

[computer]

I still use a P4C800-E Deluxe, the AN7 is a customer's. In order to get the 1:1 setting on it in the BIOS, you have to set it to "DDR400". I think the options were DDR266, DDR333 or something like that, and DDR400. The other settings (other than "DDR400") run 3:2 and 5:4 which really cut down on memory benchmarks and memory performance.

Ok, thanks for the info. People at the Abit forum don't know either how the 1:1 settings in the AN7 differ. They just won't admit it! So, thanks for being clear and upfront on that. I keep asking and they keep saying all of the 1:1 settings (3/3, 4/4, etc.) are the same, yet one guy said he got different benchmark results at each of the 1:1 settings. So, there's obviously a difference. Abit had to put them there for a reason, and so far no one knows why.