Athlon Running at Less Than Half Speed

[Aiwin]

I've got an Athlong XP 2800+ running at 1250 MHz, 12.5 X100. I can change the performance settings in my BIOS to a couple different (faster) canned configurations in addition to a manual setting option. If I go the manual route, what configuration would be best? I know AMD's 2800 value corresponds to a lower actual MHz rating, but I'm not sure how much lower. A sticker on my mobo shows the FSB as 133, so does that mean I can safely raise the CPU's FSB to 133 without worrying? If so, how high should I raise the multiplier? Is there some chance my mobo can't handle the CPU at full speed, and if so, how can I make that determination?

[SoD Stitch]

That's strange; I've got an Athlon 2800+ also, and mine is running at ~1999 MHz; sounds like your FSB is the culprit. The AMD set-up actually sends data on the both sides of the cycle, so an FSB of 133 MHz results in a true transfer speed of 266 MHz; I would definitely try bumping your FSB speed up to 133MHz and see if your computer boots. If it doesn't, your BIOS should reset itself to the default speed (100 MHz?) and boot up normally (unless you've got CMOS jumpers on your mobo; that's a whole 'nother procedure).

[Heartborne]

Also bear in mind that some CPUs throttle when not in use. Try running a cpu burn-in test and see how fast it runs then.
There is probably a power saving feature in your BIOS that you can disable to keep it running at 100% all the time.
Also, do you use that ridiculous Asus cool 'n' quiet software? It sucks horribly. It did absolutely nothing for me when I had my VERY noisy athlon 64. It might actually be doing something for you.

[saphalline]

Heartborne - The AthlonXP's pre-date C'n'Q. They have no throttling ability whatsoever.

Aiwin - There are two versions of the AthlonXP 2800+, and neither of them run at 2800 MHz. The "2800+" at the end represents a performance rating based on the original K7 CPU's (the first Athlon's). Ie, an AthlonXP 2800+ performs as well as a 2.8 GHz Athlon would (if it existed).

AthlonXP 2800+
Thoroughbred B
2250 MHz
333 FSB (2 x 166 MHz)
256KB L2
13.5x

So it's not this one. It must be:

AthlonXP 2800+
Barton
2083 MHz
333 FSB (2 x 166 MHz)
512KB L2
12.5x

Unfortunately, the Barton core revision was only supported by the last of the Socket A chipsets & mobo's. If your only options for the FSB in the BIOS are 100 MHz (200 FSB) and 133 MHz (266 FSB) then your mobo/chipset is about 2 years too old to support that CPU. You should take it out immediately to prevent over-volting it.