Modified Bios for tweaking CPU & memory speed ?

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While overclocking my new Athlon 64X2 4600+ on a MSI K8N Diamond (MS-7100)
motherboard I'm restricted by the Bios offering only memory frequency values
200, 166, 133 and 100 MHz (besides some values above 200 MHz).

I'm able to run the cpu reliably at 2772 MHz (12x231), but for that I have
to set the memory (2x512 MB) Kingston HyperX PC3200 at 166 MHz frequency.
This means that the memory is effectively running at 184.8 MHz.

If I set the memory at 200 MHz it effectively would overclock to run at 231
MHz, but the memories won't accept that frequency, even if I relax the

With my previous cpu (Athlon 64 300+ Winchester) I was able to run these
memories reliably at 221 MHz, so I know I'm giving away memory performance
with my present settings.

An ideal solution would be to find a possibility in Bios to set the memory
frequency somewhere between 166 and 200 MHz.

Some time ago I came across some modified Phoenix-Award Bios versions
offering various tweaking features not found in the official Bios versions.
I just can't recall where/in which forum(s) such modified bios files can be

Any ideas?


Re: Modified Bios for tweaking CPU & memory speed ?

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How about trying A64tweaker while in Windows ? I think it has
a setting for memory clock.

What I cannot tell you, is if all the settings listed in A64tweaker
really affect the hardware on the fly, while the processor is
running. All I can suggest is giving A64tweaker a try, and use
Sandra or some other Windows memory benchmark program, to test the

There is a three bit register in the processor, which controls
the memory clock. The AMD 26094.pdf document, only officially
defines four of the values. But this article was one of the first
to show what was happening underneath. The Rev.E processors
added a bit called OddDivisorCorrect, but I don't know how
that affects this table, or even whether A64tweaker knows
about that bit setting.

Another tool you can check into, is Clockgen. It has a
setting for memory clock, but I don't know if it is accessing
that three bit register as well or not.

There are plenty of tools to play with :-)


Re: Modified Bios for tweaking CPU & memory speed ?

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nTune also supposedly has this option but the one time I tried it my pc
crashed.  Maybe I just set it too high. :-)

Re: Modified Bios for tweaking CPU & memory speed ?

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Paul, thanks for your reply.

Have been using Clockgen for quite some time for OC, and fiddled a little
with A64-Tweaker some week ago, but only scratched the surface of its
capabilities - until now.

The thread link you provided to was what really opened my
eyes. I read it all (took some time).

It turned out that it is possible with the A64-Tweaker to employ a memory
divider between 166 and 200 MHz, namely 183 MHz, which is what I have been
looking for (in form of a modified Bios flash file). Using this divider
(183) I now have my memory running at 214 MHz instead of earlier 184 MHz,
which is a nice improvement.
In the process I also tried some other little adjustments in the various
memory timings and values that the A64-Tweaker gives acces to, but are not
accessable in Bios. The thread provided very uselful help in this context. I
actually copied and saved the most important info (for me) from the thread
into a text file for further reference.

It is very easy to test the new memory settings adjusted with the
A64-Tweaker, as the altered values are activated on the fly (click SET), and
you can test them immediately with Memtest for Windows and SuperPi or
similar, to check stability and performance. Of course there is the risk of
crashing if you go too far, but then you know the limits.

A good thing with the Tweaker is that you can save your settings to be
enforced at the next system startup, but I got the feature to work only with
version 0.31, which is the latest fully tested version, acc. to the author.
The later versions, like the latest v0.6beta, are experimental and not fully
tested by the author. I made my first experiments with that latest v0.6beta
version, and all went fine except for loading the adjusted values at Windows
startup. It simply crashed and re-booted, and I have to go into safe mode to
stop the loop.

I then downloaded the "official" v0.31 version, and now it loads the new
values at startup with no hickups, and maxed out memory performance. So it's
best to use the stable v0.31.

With that thread at I have been able to achieve my
objective. Thanks for pointing me there.


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