opq

Clocking Down Engineering Samples?

Recommended Posts

Hi, I have a 570 3.8GHz P4 Engineering Sample that lets me change the multiplier from anywhere between 14x and 19x (2.8GHz and 3.8GHz) - Do I save power and lower temperatures by clocking it at the slowest?

Share this post


Link to post
Share on other sites
Hi, I have a 570 3.8GHz P4 Engineering Sample that lets me change the multiplier from anywhere between 14x and 19x (2.8GHz and 3.8GHz) - Do I save power and lower temperatures by clocking it at the slowest?

207448[/snapback]

your major power savings will come from dropping the operating voltage, not by lowering the clock speed (though lowering the clock speed will drop power too). And very likely, you will need to lower the clock speed to get the CPU stable at a lower voltage. i.e. try running it at 3.2ghz at 80% of the original voltage (so if it's a 1.5v default, run it at 1.2v). if it's not stable, keep dropping the clock speed til it is stable.

ELiTe

Share this post


Link to post
Share on other sites
Hi, I have a 570 3.8GHz P4 Engineering Sample that lets me change the multiplier from anywhere between 14x and 19x (2.8GHz and 3.8GHz) - Do I save power and lower temperatures by clocking it at the slowest?

207448[/snapback]

You save power by dropping voltage and/or your CPU speed. You can lower your CPU speed by either lower your multiplier lock or FSB.

Be careful about lowering voltage though, transistor gates require certain power to open/close. Not enough juice supplied = gate may not open/close when you need them too = crash.

Share this post


Link to post
Share on other sites

The only reason Engineering Samples are in such high demand is you can either overclock the chip without also overclocking the chipset FSB, else you can max out the FSB at the highest performance the chipset/memory is capable of.

If you want to save power and temperature, sell the P4 for enough to build an entire cool'n quiet AMD or P-M system. The P-M will not run speedstep with the popular desktop i875 conversion, but then it already uses less power at full load than that P4 does at idle.

Share this post


Link to post
Share on other sites
The only reason Engineering Samples are in such high demand is you can either overclock the chip without also overclocking the chipset FSB, else you can max out the FSB at the highest performance the chipset/memory is capable of.

If you want to save power and temperature, sell the P4 for enough to build an entire cool'n quiet AMD or P-M system.  The P-M will not run speedstep with the popular desktop i875 conversion, but then it already uses less power at full load than that P4 does at idle.

207475[/snapback]

From what I recall, the Pentium-M uses less power at full load than the Althon 64 uses idle.

Edited by Shining Arcanine

Share this post


Link to post
Share on other sites

That's not entirely correct. It depends which Athlon64 you're using. A "Standard" Pentium M uses between 20 and 30w at full load, my Athlon 64 uses about 5-10 idle.

Share this post


Link to post
Share on other sites
That's not entirely correct. It depends which Athlon64 you're using. A "Standard" Pentium M uses between 20 and 30w at full load, my Athlon 64 uses about 5-10 idle.

207479[/snapback]

That was based off the following review:

http://techreport.com/reviews/2005q1/dfi-8...f/index.x?pg=17

I forgot that review was done without Cool N' Quiet enabled.

Edited by Shining Arcanine

Share this post


Link to post
Share on other sites
Hi, I have a 570 3.8GHz P4 Engineering Sample that lets me change the multiplier from anywhere between 14x and 19x (2.8GHz and 3.8GHz) - Do I save power and lower temperatures by clocking it at the slowest?

207448[/snapback]

Many people don't understand that power = heat, they are one in the same thing.

My wife's electric hair dryer is a 1400 Watt unit. This is both a measure of the heat it produces and the power it consumes. That's because the heat you get out is a function of the power (Voltage * Current) consumed by the device. It's called "Dissipation".

So, anything you do to reduce power consumption also reduces heat generation.

You actually save a fair amount of power by reducing clock rate. It can be as much as directly proportioal to the change in clock speed. 50% lower clock would equal 50% lower power consumption.

Think of it this way... you have an incandescent electric light on your desk. It's got a 60W bulb. If the light is on 100% of the time, the average power consumed by the bulb is 60W. If however you flick the switch on and off once per second so that the bulb is on 50% of the time and off 50% of the time, the average power consumption drops to 30W (this is in fact how many lamp dimmers work, they modulate the power going to the bulb and the bulb's output is reduced in proportion to the duty cycle of that modulation).

The reality is that even with no clocking at all, that Pentium is going to draw some power. There are "static" elements in the chip that use power independent of clock rate, and the very nature of VLSI is such that "leakage" occurs and power is consumed even though the circuit is "idle". However, 3.8 to 2.8 is nearly a 25% reduction in clock rate and power dissipation will be reduced to a near-similar degree.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now