Will It Work Or Will It Not?

There’s a story out there that 865PE/875P motherboards will not be compatible with Prescott processors. There’s a followup article here.

While we can’t completely dismiss the story, we have grave doubts about it for the following reasons:

1) The technical terms used in the article that are referred to as new standards aren’t. “VIN” stands for “voltage input” and is measured in voltage. “FMB” merely means Intel motherboard design standards, basically electrical and thermal requirements.

2) All relevant Intel documentation indicates that Northwood/Prescott motherboards are not only possible, but assumes that most if not all will. For instance, the Intel datasheet for the 875P chipset (initially released April 2003, revised May and June 2003, has the following subheading:

“For Use with the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process and the processor code named Prescott (Processor Signature of 0F3xh).”

(Don’t worry, 865 owners. Anything said or linked below about the 875P is found in Intel’s 865PE datasheet, too.)

These datasheet talks a whole lot about Prescott. While Intel recommends that 865/875 mobos be made compatible with Prescott, it does not require it.

It does say that 865/875 boards must support the VRD 10.0 (this is a name change for the VRM standard, see page 24 of the datasheet mentioned above) standard. The VRD 10.0 provides for voltage down to 0.8375.

Prescott is supposed to have a default voltage of 1.225V. Motherboards that are supposed to support both Northwoods and Prescotts will need a little extra circuitry to identify the processor type and provide the correct voltage (and voltage slope), but Intel describes just how that can be done.

Motherboards that support Prescotts are also supposed to support a bit higher amperage than earlier standards. To quote from the VRD 10.0 datasheet (page 13).

System boards supporting Intel ® Pentium ® 4 Processor with Hyper-Threading Technology1
operating at 3.06 GHz or higher and processor code named Prescott must have voltage regulator
designs compliant to applicable FMB electrical and thermal standards. For Intel ® Pentium ® 4
processors, this includes full electrical support of 70 A Icc_max specifications and robust cooling
solutions to support 63 A thermal design current (TDC) indefinitely within the envelope of system
operating conditions. For processor code named Prescott, this includes full electrical support of 78
A Icc_max specifications and robust cooling solutions to support 68 A thermal design current
(VRTDC) indefinitely within the envelope of system operating conditions.

What Probably Happened Here

As you can see, it is quite possible according to Intel to build an 865/875 board that is compatible with Prescott. It is also possible and allowable to build an 865/875 board that is not compatible with Prescott, too.

It should be noted that the source for this “information” are certain unknown mobo makers. I would not be the least bit surprised if these manufacturers have 865/875 mobos that do not meet all the necessary criteria, while others do.

This puts them at a competitive disadvantage with those who do. What to do? Why, tell a story like this one to those perhaps not likely to doublecheck items like datasheets. This would tend to keep people from buying the competitor’s product while they got up to snuff.

What To Do?

If you have already bought an 865/875 motherboard, you ought to ask the manufacturer whether or not it’s compatible with Prescott or not.

If you haven’t yet, you ought to make sure that the motherboard company says in writing that it supports the Prescott standards.


Be the first to comment

Leave a Reply