P4 notebook?

[seishino]

Ok, maybe this question has an obvious answer besides the hideous cost. I was surfing the intel site, and I noticed that the mobile P4 at 1.5 Ghz has a thermal bleed of 26W, and a core voltage of 1.3/1.2 . The standard 1.5 Ghz P4 has a thermal bleed of 62.9W, with a core voltage of 1.75.

The mobile P4 has a similar wattage to the traditional P3, and much higher upper temp tollerances. Am I missing a reason why we're not using these in desktops? Are there any motherboards that support micro-fcpga processors?

I appologize in advance if this is a stupid question. It seems like there should be some blazingly obvious answer that I'm missing. I mean, 40% of the heat? I *must* be missing something.

-C

[powergyoza]

Ok, maybe this question has an obvious answer besides the hideous cost.

I might be wrong, but is the P4-M in a different form factor that won't fit in socket 478?

[Ralf Hutter]

Ok, maybe this question has an obvious answer besides the hideous cost.

I might be wrong, but is the P4-M in a different form factor that won't fit in socket 478?

The P4-Ms are standard 478 pin CPUs. They fit fine and work fine on regular P4 Socket 478 MoBos. On desktop boards they run at a default multiplier of 12. The catch is that all the boards that people have tried them on set the default Vcore to 1.5+ Vcore, and if you read the "undervolting" thread here in General Discussion you'll see that there are very few decent Socket 478 MoBos that will allow you to undervolt.

There are guys that are doing some massive FSB OCs (220+ FSB) using these P4-Ms. There's about three or four threads in the CPU section at Anandtech and a thread at Asusboards about this topic.

For use "Silent PC" guys the issues are this: If you don't OC your CPU (no matter which speed of CPU you have) will default to a multiplier of 12 along with an FSB of 133Mhz which gives you a CPU of 1.596Ghz. The other issue is the Vcore at 1.5+ volts. Your temps won't be much (if any) lower than a desktop P4 and you'll be running at 1.6Ghz.

[seishino]

OK, that makes sense. I can see having problems finding a desktop motherboard that supports such low vcore settings, and if you did you could probably shave a higher-end AMD down to a comparable temperature for half the cost.

Still, I'd like to see someone actually do it before I pass final judgement I have yet to see any benchmarks for underclocked P4.

-C

[LeoV]

Actually, at least one person (Technonut on Anandtech) got lower voltages working by using a motherboard that supports it.

Also, if my calculations are correct, the P4M uses ~15% less power than a desktop P4 when both are at the same MHz and voltage.

When you take the 12X multiplier into account, you can run the P4M at 1.6GHz and still benefit from 533MHz QDR FSB (thus increasing per-cycle CPU performance).

This makes the P4M by far the most attractive "silent" P4 chip, in my opinion.

PS: Nice systems Ralph... they are exactly what I would like mine to become (Using 2.26B @2.5 with pal8942 on P4B533 with 1gb xms3500; 5 and 7-volted L1As; and P3/600EB for server)