VCore undervoltage... is it harmful?

Depends on the CPU. Some AMDs with "Power Now" use voltage reduction to
reduce power consumption for mobile use. While the CPU is in reduced power
mode it also clocks down (underclocks). Check out your CPU speed with the
reduced voltage, you CPU clock could have dropped with the voltage drop.

I know this isn't overclocking as such, but I figure this is the ng for
experts in CPU voltages etc, apologies if I'm off topic.

Due to some very hot weather and slightly worrying CPU temps, decided to
try
reducing the VCore on my Athlon XP 1800+. I built this system in April
2002
so I think this must be a palomino core? The mobo (Abit KR7A-RAID) had
VCore
at 1.75V (reporting 1.78) which I believe is correct for a palomino.
Decided
to try reducing it to 1.725, and the system was stable. At 1.7 the CPU
temp
had dropped from a frightening 70C to 55C.

Today decided to go mad and dropped it to 1.6V. Core temp is now 49C,
compared to reported Mobo temp of 35C.

Common sense suggests to me that lowering the voltage can't do any harm;
but
is there something I don't know? (Presumably the transistors will be
switching more slowly is the only effect I can think of). The system
appears
to be completely stable.

"Dave" wrote in message
...
Depends on the CPU. Some AMDs with "Power Now" use voltage reduction to
reduce power consumption for mobile use. While the CPU is in reduced
power
mode it also clocks down (underclocks). Check out your CPU speed with the
reduced voltage, you CPU clock could have dropped with the voltage drop.


According to the BIOS and CPUID it's running at its proper speed; and it
certainly doesn't feel any slower I tried as an experiment dropping the
VCore to 1.5V; the machine booted but stalled as soon as windows began to
load. At 1.55V it got into windows but was very unstable; so it looks like
the 1.6V its at is only just enough.

Ian