HELP - can't get lower multipliers to work on Asus A7N8X nForce2 mobo

[StevenG]

I'm really baffled by this, need some expert help. Just assembled an Athlon XP 2400+ on an Asus A7N8X motherboard. In stock configuration, the 2400+ uses a 133/266 FSB, a multiplier of 15, and runs at 2.0 GHz.

stock: 133 * 15 = 2000

I want to run the CPU at stock frequency (2 GHz), but with a 166/333 fsb. To do that, I would have to change the multiplier to 12.

desired: 166 * 12 = 2000

So, my plan was to first change the multiplier to 12, boot, and confirm with wcpuid that the computer is indeed running at 12*133 = 1600 MHz. Then I would go into the BIOS and increase the FSB to 166/333 to finish the job.

But I never got past the first step. When I changed the multiplier setting from Auto to Manual, then reduced the multiplier to 12, the PC refused to boot. The POST screen terminated with "WARNING - CPU has over speed" (sic) and would not go any further. The only way to proceed is to go into BIOS setup, and the only way to get the PC to boot is to set the multiplier to Auto.

This makes no sense - when I changed the multiplier to 12, I was UNDERclocking the CPU from 2000 to 1600. Why does the BIOS think I am overclocking? Any ideas what is going on here?

 

[randomlinh]

hey, you got further than I did. From what i understand, you cannot go to any lower multipliers w/o connection the bridges to unlock the lower multipliers.

I cannot even post setting to any lower multipliers w/ the 166fsb (have not tried lower w/ 133fsb tho... maybe i should). But others have unlocked the chip to get it working fine. The only caveat is you top off at 12.5x multiplier I would really like to use 13 since these cpu's seem to be overclocking quite well.

 

[StevenG]

Is it possible that I need to unlock the CPU to enable the lower multipliers? This doesn't seem right, as I've read in several places that the XP2400+ comes unlocked. Also, if the processor were locked, I would expect the multiplier field in the BIOS to be disabled. It isn't disabled - I am able to select any multiplier in the BIOS, I just can't get the computer to boot after I change it; I get that damn "CPU has over speed" message.

Could it be that the current BIOS in the A7N8X simply doesn't work properly with lower multipliers? Will Asus fix it?