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p4: how many watts is it radiating?

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Fluxer

Member
Joined
Mar 2, 2002
Location
New York
Can someone please give me a definite answer or formula to calculate the watts of a given CPU?

I want to know how many watts my P4 Northwood is putting out. It is a 1.8a @ 2.51 using 2.0 Vcore. I suspect it is outputting a lot of watts, but i'm interested in knowing how many.

I downloaded and tried using the program Radiate and it says my CPU is putting out 208 watts :eek: which I really don't think is the case :D
 
It will be putting out at least 150w, using 2v is going to kill your cpu fairly quickly.
 
the NW 2.53ghz has a Thermal design power of 59.3W (according to intels s-spec list)

so i guess that at 2.0v you'd have about 65-70W
 
The formula for calculating power is:

Pn = Po * (Fn / Fo) * (Vn / Vo)^2

where:

Pn = Power generated under new settings
Po = Power generated under old settings
Fn = New frequency of CPU
Fo = Old frequency of CPU
Vn = New voltage of CPU
Vo = Old voltage of CPU

Your P4 1.8A with a default voltate of 1.5 V generates approx 50 W at default settings.

So your new power at 2.51 GHz and 2.0 Vcore is...

Pn = 50 * (2.51 / 1.8) * (2.0 / 1.5)^2 = 124 W
 
hmm .. according to your formula, a 1.6 NW o/c to 2.4ghz gives 70.2W (at 1.5v)

according to intel, the 2.4 NW gives 57.8W

who's right? the formula? intel? not comparable due whatever? :confused:
 
amd_builder said:
Can someone please give me a definite answer or formula to calculate the watts of a given CPU?

I want to know how many watts my P4 Northwood is putting out. It is a 1.8a @ 2.51 using 2.0 Vcore. I suspect it is outputting a lot of watts, but i'm interested in knowing how many.

I downloaded and tried using the program Radiate and it says my CPU is putting out 208 watts :eek: which I really don't think is the case :D
that is alot of juice to be running for that speed. it really takes that much to get to 2.5?
 
> hmm .. according to your formula, a 1.6 NW o/c to 2.4ghz gives 70.2W (at 1.5v)

> according to intel, the 2.4 NW gives 57.8W
> who's right? the formula? intel? not comparable due whatever?

formula is correct, intel is correct.
NW [email protected]: 38.7W/1.6*2.5 *(1^2)= 58.1W.
That pretty much is the same as the 57.8W from the 2.4.
(The formula is quite good, but not perfect, since there is a core-frequency independant part too, some of it because of the i/o transistors clocked with the FSB, some of it because of current leaks in the transistor gates. In absolute numbers, this is probably around as much as the cpu uses in halt mode).

mczak
 
mczak said:

formula is correct, intel is correct.
NW [email protected]: 38.7W/1.6*2.5 *(1^2)= 58.1W.

take a closer look at the s-spec listing at intel.com

there's the OEM 1.6A - which is listed with 38W (SL62S) and
there's the BOXED 1.6 - listed with 46.8W (SL668)

Using the Boxed' (which I think almost EVERYONE has) will mess up the formula.


Btw - I'll be dammed if anyone can explain the differences between the OEM and the Boxed CPU to me. What in God's name did Intel do to the OEM in order to make it run cooler?
 
that is alot of juice to be running for that speed. it really takes that much to get to 2.5?

Yep, it takes a lot of voltage to run 100% stable in Prime 95. Its a rather voltage hungry 1.8a...

I think I can run it at 2.4 using 1.825 Vcore but I like 2.51 better, esepcially since I can run my RDRAM at 4x with that FSB. If I keep it at this speed, I won't be surprised if it dies soon though.

Thanks for the voltage formula. 124 watts is a lot of heat :eek:

Also, i'm using Windows XP Professional which is sensitive to overclocking errors.
 
Last edited:
@Redphex:
you're correct, the intel site says the 1.6A OEM and boxed are different. (I think the 1.6A OEM is what was called "small form factor" (SFF) for low-noise systems, but I can't find any reference to that at the moment).
That said, I strongly believe this is just a difference in the official specification - intel can surely change the law of physics, but unfortunately only on paper ;-)
(Can't check the differences in the datasheet, since according to the datasheets, the 1.6A and 1.8A don't even exist - I'm sure the NW datasheet included those, but it seems they are gone - wtf? http://developer.intel.com/design/Pentium4/datashts/)

mczak
 
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