Wednesday, June 10, 2009

Adventures in Overclocking

So, as you may have seen in previous posts, I've been having problems with my new rig.
First off, when it arrived, the fan had fallen off in transit.
I'm working with a

  • Phenom II X4 955 BE
  • Gigabyte GA-MA790XT-UD4P.
  • 2x2Gig DDR3 1600 RAM.
  • Gelid Silent Spirit Cooler

Then, it appeared that the BIOS hadn't been updated on the board to support the chip they were selling it with, so the thing was running at 800MHz, instead of 3800MHz.
I downclocked it back to x16 multiplier @ 200Mhz Clock and was seeing a very stable 3200MHz.

So, to overclocking.

Notes
I'm using Windows 7, release 7100, 64 bit. Almost every report I've read said that 32 bit windows allows much greater overclocks.
Also, benchmarking takes TIME. You'll need to run a new setup for at least 3 hours to make sure they're stable.
Fortunately (or not), problems tend to appear in minutes.

Useful Links
There are a few things I've learnt about this, and a few great articles out there for the beginner.
Overclocking Basics
http://www.tomshardware.com/reviews/phenom-ii-overclock,2267.html
http://blogs.amd.com/play/2009/04/22/overclocking-101-with-the-amd-phenom-ii-x4-955-black-edition-processor/
http://www.pcstats.com/articleview.cfm?articleid=2393&page=2
http://www.pcstats.com/articleview.cfm?articleid=2393&page=2

Monitoring tools:
CPU-Z, Hardware Monitor, Core Temp, Speedfan, GPU-Z
Core temp creates log files, allowing you to see what happened after a crash, or if you were AFK, but all are pretty essential (and free).

Gadgets:
All CPU memter

Benchmarking tools:
3dMark Vantage (I bought it - it's pretty awesome, but there's a free version too).
Prime95
wPrime


Just overclock me, damnit.
The thing that becomes immediately obvious is that there's no silver bullet for this stuff. No one setting will work for everyone.
That being said, if you want a very simple overclock, whack the multiplier up to x18 if you have a stock cooler.
You'll see very stable performance at 3600MHz, without changing anything else.
To do this, hit enter when your computer boots, and go into MIT -> then just change the multiplier value.

The basics - before you start.
There's a huge amount of reading to do, though. Where do you even begin?
Well, it seems one of the big advantages of the Black Edition Phenoms is that they come 'unlocked'. This means you can ramp up the multiplier in the BIOS to get easy overclocks.
However, before we even do that, you want to optimise your memory. Mine runs at 8x, dual channel. So, 8 * 200 = 1600MHz.
Easy enough. I upped the VDimm (DDR3) voltage to 1.8v, which Corsair recommend for their RAM. I also adjusted the timings manually in the BIOS.
You'll need to find the settings for your RAM, and do the same.

The basics - AMD Overdrive
Many people use AMD Overdrive. I can't get this to run, despite claimed support from AMD for both Windows 7 and the motherboard. Others may see different levels of success. My particular error message was that it couldn't start the service, due to the path not being found. Oh well.
You may have more luck. It's available over at AMD.

Using the BIOS.
Fortunately, all the serious sites didn't really use AMD overdrive, preferring the scary route of the BIOS.
I won't lie. Poking around in your BIOS can be daunting, and if you get something wrong, you can nuke components.
Overclocking (or attempting to) will void your warranty. However, as long as you make small changes each time, you should never run into problems.

So, to access the BIOS, you need to push as your computer's booting, ideally when it's searching for the IDE drives, or when the splash screen tells you to.
Once in there, you want to enter into the MIT section. Most things should be set on auto.

The first thing you want to do is disable AMD Cool'n'Quiet.
Then, you can get going.

My first overclock
The default for the 955 is a multiplire (CPU Clock Ratio) x16, with a clock speed (CPU Frequency) of 200MHz. So, simple maths, 200x16 = 3200.
You'll want to download CPU-Z, which lets you monitor how quickly your processor is actually running.
You may find you need to flash the BIOS on your motherboard, if CPU-Z is reporting 800MHz for your chip.
So, change the CPU Clock Ration to 'x18'. This will take you to 3600.
Then push escape, f10, enter. This will return to the menu, save the bios and reboot.
Next time your computer comes up, it'll be running at 3.6Ghz, which should be stable at stock voltage.

Now, break out your stability test (prime95, for example) and run it for 15 mins. It should kick the bejesus out of your processor. I am running the CPU Meter gadget for Windows vista/7, which shows a very basic bar graph for CPU utilisation. It's sufficient for my needs. You may want to shop around.

If everything is stable after 15 mins on this low overclock, you should be in business.
Now, reboot, enter BIOS, and knock the multiplier up one click, to x18.5. This should give a 3700 operating speed.
Let it boot into windows, and see what happens. Run the stability test.

Wait for it to crash. At least, it crashed on mine. So, the next thing is to go back into the BIOS, and up the VCore voltage.
This is the number you can see on CPU-Z and a number of other tools, which should be around 1.3 at stock (possibly 1.35).
You want to bump this up .05V, and then boot to windows. Re-run the stability tests.

If anything crashes, go back and up the voltage again. I got stable results for x18.5 at 1.425V.

Then, once you have stable results for x18.5, go and change again to x19.
Personally, at this point, I had to up the voltage to 1.52 to get it to boot at all.
This meant that my cooler couldn't cool things quickly enough at all, and we hit 64C in a few seconds.
I stopped the tests and decided it wasn't wise to continue.
If I could have made the chip run at lower voltages, I might have been in with a chance, but it falied miserably at any lower voltage.

The Clock Speed
Next, we revert all the settings back to standard.
What? Why? I hear you scream.
Well, now we've pushed the limits of the multiplier, we want to see how much we can overclock the clock speed.
This means that the multiplier will still be x16, but by moving the 200 value, we can still an increase.

This works in exactly the same way.
First, up the Clock Speed value to, say, 210, Then reboot, and run some tests.
At 210, with a x16 multiplier, you're running at 3360MHz.
Please note, this will also increase the speed of your RAM, HT Link and NB frequency.
http://en.wikipedia.org/wiki/Front_side_bus
If your RAM is now operating over its recommended settings, scale back the multiplier. It's always better to be a bit low than a bit high.

I'm still at the very early stages of this process, but I seem to have a stable build on a clock speed 230 at 1.425V, and I want to push it further.


Current thoughts
There are lots and lots of great guides out there, and many many documents filled with scary acronyms.
This is one of the best
http://www.xtremesystems.org/forums/showpost.php?p=3771025&postcount=240
but it's pretty hardcore.

I'll update tomorrow with my new findings.

1 comment:

Xioros said...

Good to hear you're also starting with overclocking!

I personally love it :D
I run my Intel Core i7 2600K @ 5,2 GHz (instead of the "stock" 3,4)...
That's a massive 50% overclock :D

I also overclocked my memory and my GTX 680's SLI (200 MHz offset)

If you need any help overclocking, check out overclock.net or this website: Overclocked Gaming PC