[fc5] I seem to have misplaced a few MHz

[Michael A. Peters]

IBM Thinkpad T20 - 700MHz.
The kernel sees it as a 700MHz - from /var/log/messages:

Apr 27 00:16:37 atlantis kernel: Detected 697.130 MHz processor.

That seems consistent (always 697.xxx)

but -

[root at atlantis ~]# grep "MHz" /proc/cpuinfo 
cpu MHz         : 550.000
[root at atlantis ~]# 

I went through the BIOS and set everything to maximum performance, in
case it maybe thought it wasn't plugged in - no change.
I added "acpi=off" to the boot options - and indeed, it booted without
acpi, but /proc/cpuinfo still reports 550 MHz.

Does anyone know what might be causing this?
The CPU itself does support throttling (wanted when not connected to AC
power) - and it seems that something is in fact causing it to throttle,
if memory serves - 550MHz is what it throttles to when I disconnect it
from AC - but now, I've told the bios to use maximum performance under
all conditions and I'm not getting the full CPU speed which the kernel
does correctly detect.

Any suggestions? This hardware is slow enough as it is ;)