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From: GT on 19 Apr 2010 09:28
I am considering a 2nd hand purchase. The online manual doesn't make this
clear, so does anyone know if the above motherboard gives full control over
the CPU voltage - down as well as up - I want to experiment with
undervolting a core2duo chip for ultimate silence purposes.


From: Paul on 19 Apr 2010 16:58
GT wrote:
> I am considering a 2nd hand purchase. The online manual doesn't make this
> clear, so does anyone know if the above motherboard gives full control over
> the CPU voltage - down as well as up - I want to experiment with
> undervolting a core2duo chip for ultimate silence purposes.
>
>

It gives the appearance of being programmable.

http://www.ocworkbench.com/2008/asrock/Penryn1600SLI-110dB/g5.htm

CPU Voltage [Manual]
Voltage Value [1.60000V]

http://www.ocworkbench.com/2008/asrock/Penryn1600SLI-110dB/g1a.htm

The VCore regulator is the same as the one on my (previous) motherboard. L6714D.

http://www.ocworkbench.com/2008/asrock/Penryn1600SLI-110dB/IMG_0484%20copy.jpg

I guess it is working. They claim to have keyed in 1.4000 volts
and CPUZ shows a lower setting (1.368), so I guess that means there is a
working VCore offset capability on the board. (Since the VID pin values
are range limited by Intel, if you want a boost, it is applied outside
of the normal VID pin control mechanisms. The ST L6714D has an offset pin,
so you can change the output voltage that way. I had to volt mod my Asrock
board, since there is no VCore BIOS setting on my particular model of
motherboard.)

http://www.ocworkbench.com/2008/asrock/Penryn1600SLI-110dB/asrock%20penryn1600sli-110db%20oc%20to%20495x6%20copy.jpg

Since it is Asrock, I'd be more suspicious of the implementation.
I've owned one Asrock board, and that was enough for me.

According to this, the offset pin is only positive. I think this is
the page I found, to help me do the volt mod. Your board probably
already has some mechanism tied to that pin, and perhaps not
exactly the way the datasheet does it.

http://forums.vr-zone.com/overclockers-hideout/192571-volt-mod-done-right-asrock-775dual-vsta-l6714.html

From a link on that page, this is the VCore regulator datasheet
for the regulator on the Penryn1600sli-110dB.

http://www.st.com/stonline/products/literature/ds/12187.pdf

"12.2 Offset (Optional)

The OFFSET pin allows programming a positive offset (VOS)
for the output voltage by connecting a resistor ROFFSET vs. SGND"

So that leaves the question, as to whether there is some way to
effectively undervolt the thing, without screwing up any of the
other parameters of the design. Maybe Asrock figured out some
way of doing that, but my suspicion is, you'll be turning on
EIST and just relying on the Intel range-limited lower limit
to be used, when the system is idle. In other words, if the
offset pin cannot apply a negative offset, you get to enjoy
the lowest voltage the processor supports, simply by turning
on Intel SpeedStep (EIST).

HTH,
Paul
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