help! how do I set voltage below 1.5V on A7N8X-E Deluxe ?

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I am using a A7N8X-E Deluxe and I am using the mobile Athlon XP 2200+ (35W)
p/n  AXMD2200FJQ4C

I need to underclock this CPU, and although the Asus literature and owner's
manual says I should be able to adjust the voltage (CPU Vcore) down as low
as 1.1 V, it seems it will not allow me to set this processor below 1.5V and
even the stock voltage for this CPU is 1.35V !!

I have it set on "Manual" Vcore adjustment in the BIOS, it will let me take
it up higher than 1.5V, just not lower.

what am I doing wrong?



Re: help! how do I set voltage below 1.5V on A7N8X-E Deluxe ?

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"what am I doing wrong?" - You're using an Asus board :-)

The BIOS that Asus ships, do not allow undervolting. What
damage undervolting would do, is unclear to me, unless they
are concerned about violating the spec'ed ranges of voltages
for core and I/O voltages. On some chips, you can get current
flowing where it isn't supposed to flow, by pushing the rails
too far from one another.

In any case, get a copy of the tuner application (NVSU). I don't
know if this is the most current version - you might check the
download page and see if there is something more recent listed.

When you unzip that file, have a look for nvsysvals.ini .
With a text editor, change the "cpu_min" value from 1.75 to
1.1V, as I think that is the lowest value allowed. After
saving the file (and checking that the extension is still
.ini), install the package. Since there is one "ring0" software
module that will be installed, you'll likely need to reboot.
After that, try moving the slider for Vcore, and then,
using Asus Probe or some other utility, verify the voltage
measured for Vcore.

Perhaps that will allow Vcore to be dropped a bit. This thread
mentions that a setting of 1.425V is as low as it will go.
This limit could depend on the version of BIOS you are
currently using.

I've never used that utility, and cannot comment on its
stability or usefulness. (Assuming it is a real-time utility,
and not just a BIOS CMOS settings hack, if you move a
slider too far, the machine could crash or freeze.)

The other option is to do some hard core mods to the Vcore
circuit. Disconnecting the L6917BD from the VID lines, then
running the VID pins from a DIP switch, would be one way to
set the voltage manually. Once the L6917BD digital control
inputs are disconnected from the rest of the board, the
BIOS doesn't get to say anything about the voltage. There
are simpler analog techniques for tweaking the voltage,
but they can add noise to the circuit, and without good
diagnostic equipment, you cannot tell what you are doing
to the circuit.

I don't know if hacking the BIOS would do the job or not.
There are tools like modbin, that expose more settings in
the BIOS interface, but sometimes even though a setting is
shown in a BIOS screen, there can be other code in the
BIOS to deny the command. On some motherboards, for example,
the Vdimm shows four possible values, when the actual regulator
circuit only has two possible values in hardware.

You might look on, as the forums have people
who hack BIOS, and maybe someone has succeeded in doing
such a mod. You never know...

Good luck,

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