I have a P4B motherboard and I want to upgrade my CPU from a 1.5Gh to a
2.5Gh. The 1.5 Gh CPU has a core voltage of 1.75 and as soon as you go
above 2.0 Gh all the CPU's use 1.5v. How is this handled? Does the CPU
itself take care of the difference? I know I need a bio upgrade. Does this
solve the voltage difference?

Thanks

the motherboard will set the voltage automatically

"Crhoff" <cr-nospam-(E-Mail Removed)> wrote in message
news:u4qee.3678$(E-Mail Removed)...
>I have a P4B motherboard and I want to upgrade my CPU from a 1.5Gh to a
>2.5Gh. The 1.5 Gh CPU has a core voltage of 1.75 and as soon as you go
>above 2.0 Gh all the CPU's use 1.5v. How is this handled? Does the CPU
>itself take care of the difference? I know I need a bio upgrade. Does this
>solve the voltage difference?
>
> Thanks
>

In article <u4qee.3678$(E-Mail Removed)>, "Crhoff"
<cr-nospam-(E-Mail Removed)> wrote:

> I have a P4B motherboard and I want to upgrade my CPU from a 1.5Gh to a
> 2.5Gh. The 1.5 Gh CPU has a core voltage of 1.75 and as soon as you go
> above 2.0 Gh all the CPU's use 1.5v. How is this handled? Does the CPU
> itself take care of the difference? I know I need a bio upgrade. Does this
> solve the voltage difference?
>
> Thanks

The newer processor's VID pin codings are a subset of the
older slower processor's VID codings. Old processor goes
from 1.1 to 1.85, newer processor 1.1 to 1.6V.

P4 FSB800 processor datasheet (doc 298643)

Processor Pins
VCC_MAX
VID4 VID3 VID2 VID1 VID0
1 1 1 1 1 VRM output off
1 1 1 1 0 1.100
1 1 1 0 1 1.125
1 1 1 0 0 1.150
1 1 0 1 1 1.175
1 1 0 1 0 1.200
1 1 0 0 1 1.225
1 1 0 0 0 1.250
1 0 1 1 1 1.275
1 0 1 1 0 1.300
1 0 1 0 1 1.325
1 0 1 0 0 1.350
1 0 0 1 1 1.375
1 0 0 1 0 1.400
1 0 0 0 1 1.425
1 0 0 0 0 1.450
0 1 1 1 1 1.475
0 1 1 1 0 1.500
0 1 1 0 1 1.525
0 1 1 0 0 1.550
0 1 0 1 1 1.575
0 1 0 1 0 1.600

P4 1.4 to 2.0 GHz processors (doc 249887)

Processor Pins
VID4 VID3 VID2 VID1 VID0 VCC_MAX
1 1 1 1 1 VRM output off
1 1 1 1 0 1.100
1 1 1 0 1 1.125
1 1 1 0 0 1.150
1 1 0 1 1 1.175
1 1 0 1 0 1.200
1 1 0 0 1 1.225
1 1 0 0 0 1.250
1 0 1 1 1 1.275
1 0 1 1 0 1.300
1 0 1 0 1 1.325
1 0 1 0 0 1.350
1 0 0 1 1 1.375
1 0 0 1 0 1.400
1 0 0 0 1 1.425
1 0 0 0 0 1.450
0 1 1 1 1 1.475
0 1 1 1 0 1.500
0 1 1 0 1 1.525
0 1 1 0 0 1.550
0 1 0 1 1 1.575
0 1 0 1 0 1.600
0 1 0 0 1 1.625
0 1 0 0 0 1.650
0 0 1 1 1 1.675
0 0 1 1 0 1.700
0 0 1 0 1 1.725
0 0 1 0 0 1.750
0 0 0 1 1 1.775
0 0 0 1 0 1.800
0 0 0 0 1 1.825
0 0 0 0 0 1.850

******
And for some more trivia...

Prescott is even newer, and it adds one more
VID signal. Voltage range is 0.8375 to 1.6000V
The "OPTIMIZED/COMPAT" and the "BOOTSELECT" pins allow
a flexible motherboard to support older processors
and newer processors. The ADP3181 regulator, for example,
can work with 5 or 6 bit VID codes (pg.22).

http://www.analog.com/UploadedFiles/...1ADP3181_0.pdf

Not all FSB800 motherboards can support all types of
S478 processors. It really depends on whether the
regulator can support all types or not, and more pins
than just the VID are needed to make the necessary
distinctions. With Asus, checking the "cpusupport" page,
and interpreting the descriptions of the processors
according to whether they are Willemette, Northwood,
Prescott, Celeron, CeleronD, is necessary to figure out
just how flexible the Vcore regulator might be. It would
be too simple to explain it in plain english in the
manual (i.e. Vcore VID types, max Vcore current, load
line types, like 04A, 04B, 05A, 05B and so on).

Paul