Underclocking an AMD BE CPU.

[Refreshment]

Greetings.
Don't have a lot of experience with CPU clock speed manipulation. Anyway the CPU is an AMD X2 5000+ Birsbane Black Edition processor. I have been undercloacking it with MSI Dual Core Center and recently with AMD Overdrive.

In the case of Dual Core Center by touching only the FSB option reaching 1993 mhz.

And with AMD OverDrive setting the CPU Core Multiplier to 9.5x for a total of 1900 mhz.

For both cases i get 1/2 Celcius below stock speeds.This is as low as i can get withouth the system booting itself up.

So i have the following questions:
What risks do i incur when i downcloack the processor this way? Could i damage it with extended use?

Any other sugestions on how to downclock it even more? Voltage manipulation maybe?

And finally is there a page where i could see what settings users with similar processors use, like a database of processors tweakers or something?

Thanks for your time.

 

[Albuquerque]

What are your goals here? Decreased heat / power usage? General curiosity?

You may be running into problems with bus synchronization after a certain point; turning down the multiplier is probably a more effective way to keep the system stable while reducing CPU speed. Lowering voltage is also a good idea, at least for power and thermal envelope kinds of stuff.

There will be a lower limit where the CPU simply will not be stable at a given clockspeed, but it's probably quite a bit below 2Ghz. The chances of damaging the CPU are essentially zero, you're more likely to corrupt a bunch of data on your drive.

My E8400 (3Ghz / 1333Mhz FSB Intel part with a 1.225VID) would do 1.2Ghz (200 x 6) at 0.6v stably, which was the bottom of the line for all of my motherboard's CPU voltage and speed settings. I'd wager you could get pretty close to the same with a bit more work...

 

[Refreshment]

What are your goals here? Decreased heat / power usage? General curiosity?

Now that you put it that way... is all of them

So from what you are saying Albu, since i've been only punching the multiplier, my next step would be a to start decreasing voltage also? I heard i should do it in 0.025V increments.

So it'll be like a .5x clock and .025V.

Anything to add regarding my other questions? And i cant understand the memory tweaking mechanics is there a good guide around (from an spyware free website) where a dummy like me could get a clue.

I want to underclock the IGP (780G motherboard), whats the deal with this one?

 

[Davros]

ive got a pentium 2 400mhz, why not buy that

 

[entity279]

An why not at least also undervolt?

 

[Blazkowicz]

my CPU is a sempron LE-1100, default 1.25 volt.

I use rmclock to both undervolt and underclock, and it's done dynamically depending on CPU load ; three steps at 4x, 6x and 9.5x (highest) multiplier. It's basically using the features that are here for Cool'n'Quiet.

voltages are 0.85V for the lowest and 1.175V the highest (middle step, it was linearly calculated by the program).
the bus is actually overclocked by 20%, so depending on CPU load it's either underclocked or overclocked, and undervolted in all cases
Undervolt brings big results (squared) : stock or overclocked, 6% voltage bring 13% power reduction, underclocked it's a whopping 54%, add to that CPU frequency which scales linearly.

first thing I would aim for is to find the lowest voltage that works at stock speeds. (undervolt gives instability when it gets too weak, but the CPU isn't in danger I think)

Strangely enough, the lowered voltage I used works nice with a 25% o/c but if I want to push it, I won't really get far with overvoltage. I got like 2.66GHz with 1.4V (2.37GHz on 1.17V), stable but the mobo often resets itself, and those are gains you have to bench for. I'm very fine with that lowly CPU given the low power and cost and adequate perf.

 

[nutball]

If you browse around these forums

http://www.silentpcreview.com/forums/

particularly the CPU sub-forum, you'll find a boat-load of info about underclocking and undervolting.

 

[ShaidarHaran]

You under-clockers are all crazy. You're going the wrong direction.

 

[Refreshment]

ive got a pentium 2 400mhz, why not buy that

Thanks for the sugestion. I have a beast such as this and it even runs withouth cooler. But its kind of hard having to switch the mother board any time i want to play a prettier version of solitary, Windows 95 version is an ugly duckling

@Blazkowicz: Very informative. Curious about that rmclock application, i must check it as soon as i adjust the one im using now, AMD OD. Really amazing the way you set up works. Following your suggestion to "find the lowest voltage that works at stock speeds" right now.

@nutball: Thank you, this is the kind of site i was asking in my original post. Really useful. There's a very insightful thread with people posting their specs and the ranges they achieve when undercloacking. Now looking for a guide that explains the memory stuff.

You under-clockers are all crazy. You're going the wrong direction.

The Existentialists of the CPU world. Who gets them?

 

[Mariner]

CrystalCPUID is very easy to use and I'd recommend it for undervolting/underclocking. Very easy to set up so that full CPU speed is available whenever required - a bit like Cool'n'Quiet on steroids, if you will.

As nutball recommends, you'll find plenty of info about using this software (or RMClock as an alternative) on SPCR.

Why do we underclockers do it? Why, to save energy and/or silence the PC, of course! How crazy is that? Erm, not in the slightest, especially when compared to overclockers and their shenanigans messing around with liquid nitrogen, refrigeration units or delta fan screamers!

 

[ShaidarHaran]

Bah I say! It's balls to the walls or none at all!

 

[Albuquerque]

I undervolt all of my laptops via RMClock - pretty much every Core and Core 2 laptop chip can run at about 0.2v lower than "stock" at it's fully rated speed. I also use it to force lower speed thresholds so that it doesn't "pop up" to high speed if the CPU usage spikes temporarily.

The desktop, on the other hand, is all about going faster, not slower.

 

[homerdog]

I run my E6750 at 3.2GHz (up from stock 2.66) undervolted to 1.26V (from 1.35). I'm simply flabbergasted at how awesome the Core 2s are.

 

[chavvdarrr]

rmclock rules
cpu.rightmark.org is the site

 

[HMBR]

i'm using crystalcpuid for 1.5 years for underclock, I had some problems with rmclock, I'm using a brisbane g1 4000+, not very good for OC, but I have 3 options, one is 1000mhz with 0.8v another is 1.8ghz with 1.05v and the other 2600mhz with 1.28v, I let the software control dynamically the clock, just like cnq... and if I want I select a fixed clock, the lowest clock I tested was 600mhz with 0.8v, works very well...