how low can i go

[oldman420]

i have an xp 200 barton 1.35v cpu on the way and i was just wondering if i underclock it say to 500 mhz would i be able to lower the vcore to as low as 1 v?
is there any risk to the cpu from undervolting it?
tai folks

 

[Yanagi]

No risk involved with undervolting AFAIK. You could get away with it. in the end it depends on how low your mobo can go. Just take it in small steps. underclock and run with default vcore. then lower it one or two steps at a time and run prime for a while to see if its stable repeat until its unstable and raise vcore one notch. there you have it. Your lowest stable VCore

 

[oldman420]

thanks i will be using an nf7-s board so i can get as low a 1.0 all the way to 2.0 vcore.
it seems like i may be able to get this cpu to run at 10-20 watts at 500 mhz
any guesses

 

[DaNorthface]

it's useless at 500 mhz though

 

[MDE]

Originally posted by: DaNorthface
it's useless at 500 mhz though

Probably better than a VIA C3 @ 900 though...

 

[oldman420]

it will work fine for a file server i have beeen running my xp2500 @ 600 mhz and it does the job. i keep me main rig at 2.2 or better for gaming etc.

 

[imported_smilingcrow]

Originally posted by: oldman420
thanks i will be using an nf7-s board so i can get as low a 1.0 all the way to 2.0 vcore.
it seems like i may be able to get this cpu to run at 10-20 watts at 500 mhz
any guesses

Once you know the power consumption and voltage of a CPU, its quiet easy to calculate its power consumption at lower settings. It won?t be 100% accurate but should be within 95% most times.

Power is a function of the square of voltage.
What that means is that if you double the voltage, the power goes up by 2* 2 = 4 times.
This means that getting the lowest voltage possible is essential for low power output.
1V sounds pretty good for an Athlon XP. The Athlon 64s can handle 0.8V easily but I?m not sure if the XPs can handle that or more importantly if any boards support that? Unless you are using clockgen to lower the settings?

Power and Frequency relate in more or less a linear way. Double the frequency at the same voltage and the power doubles.

You can use this formula to make calculations:

Power = Volts * Volts * Frequency

I don?t mean that this formula has a real meaning, but just that it symbolises the relationship between these 3 factors.

For an imaginary XP chip say it had the following values:

Power = 70W
Freq = 2000 MHz
Voltage = 1.7V

If you change the Freq to 1,000 and the voltage to 1.3V the formula for the new power rating is as follows.

Note:
P1 = original power rating
V2 = new voltage rating etc


P2 = P1 * F2 / F1 * (V1 * V1) / (V2 * V2)

P2 = 70 * 2000 / 1000 * (1.3 * 1.3) / (1.7 * 1.7) = 20.5

If you can get to 1V you should be under 10W.

I used to passively cool a Celeron 600 in a system that only had a power supply fan. That was rated at 1.5 but my motherboard went down to 1.3V which I calculated equated to 9V from the stock 12.5.

Try the forums at www.silentpcreview.com
They have some hardcore under-clockers there.
One guy is running an A64 @ 1 GHz @ 0.9V which equates to only 15W.

 

[jswjimmy]

i have my xp 1800 running a 1.1volt at the stock speed of 1530mhz

 

[ectx]

Oh you mean voltage..

 

[Vette73]

500mhz ? at 1Volt you probable can get 1Ghz out of it at 1volt.

 

[jswjimmy]

Originally posted by: Marlin1975
500mhz ? at 1Volt you probable can get 1Ghz out of it at 1volt.

yah with the extra cache it will need more power than my xp1800. so 1 ghz sounds good.