AMD Radeon HD 6950 to HD 6970 Mod

[paroh]

source
AMD Radeon HD 6950 to HD 6970 Mod | techPowerUp

Introduction

A few weeks ago AMD released the Radeon HD 6970 and Radeon HD 6950. Both cards are based on AMD's new Cayman core which is their first graphics processor to use a VLIW4 shader configuration.

Just like on all other similar products, AMD's two Cayman variants, called Cayman Pro and Cayman XT, are based on the exact same GPU silicon. The model variant a GPU chip becomes is decided after the die is produced, at some point before it is put on the card. Creating new SKUs from the same silicon by locking features has been common practice in the industry since at least the Radeon 9500 in 2002.

This article is to unlock the Radeon HD 6950. The HD 6970 has nothing that can be unlocked.


The picture above shows the disabled HD 6950 shaders in red. When unlocked, these deactivated units become active, resulting in a substantial performance increase.

AMD has two methods of locking the shader count on all of their recent GPUs. The first one relies on fuses inside the GPU, or on the substrate - a mechanism similar to Intel's multiplier locking. It is not reversible as far as we know. The second mechanism is the one we are interested in, AMD can configure the VGA BIOS in a way that it disables extra shaders, in addition to the ones disabled via the on-die fuses. This method is mostly used to create engineering samples or reviewer cards that match the target specifications. Usually production cards come with the shader count configured in the fuses, so that it can not be changed.

Apparently currently shipping Radeon HD 6950 cards from all manufacturers - which actually are all the same card with different sticker - have their shaders locked via the BIOS method, so we can exploit it easily.

Unlocking the shaders


Unlocking the additional shaders is done by flashing the card with a HD 6970 BIOS. You can find a few in our VGA BIOS collection. Any of these BIOSes will work on any reference design HD 6950 card. You could use the ASUS BIOS which comes with higher clocks & Overdrive limits and enables voltage changes via SmartDoctor, or stick with one of the reference BIOSes in case you are afraid the clocks might be too high.

I will describe the method for flashing from within Windows, which is safe enough on these cards because of the dual BIOS feature that enables easy recovery.

1. Grab ATI Winflash from here (32 & 64-bit).
2. Download HD 6970 BIOS. The Sapphire one I linked to will work on all reference design cards from any vendor.
3. Make sure the BIOS switch on the card is set to the 1 position (pictured further down if you don't know where it is).
4. Run ATI Winflash, click Save to save your BIOS, so you have a backup in case something goes wrong.
5. Load the HD 6970 BIOS into Winflash by clicking Load Image, followed by Program.
6. Let the flashing process complete and reboot your system.
7. Check the shader count using GPU-Z, it should show 1536. Make sure you use the linked version of GPU-Z, the official 0.4.9 version does not support HD 6900 Series properly. If you see a shader count of 1600, your GPU-Z version is outdated and you should get the one from the link here.
8. Check stability in Windows desktop applications and games.

If you get an error like ID mismatch or Could not erase ROM, then you'll have to do some extra work in a Windows command prompt (or DOS): Run atiwinflash -unlockrom 0 followed by atiwinflash -f -p 0 bios.bin where bios.bin is the path and filename of the HD 6970 BIOS you downloaded.

Feel free to post in the discussion thread for this article if you need additional assistance with the flashing process.

Testing


We can see that enabling the shaders without any clock increases improves performance. Once the clock speeds are adjusted to match the HD 6970, the card effectively performs just as well as a full blown Radeon HD 6970.

What if something goes wrong?
So you flashed the BIOS and your card doesn't work for one reason or the other?
If your card boots fine but does not work reliably in 3D, you can just boot the card and flash back the original BIOS of your card (that's why you should always save your BIOS before doing any flashing experiments.



In case your card does not boot at all you can use AMD's new backup BIOS feature:

1. Set the BIOS switch (pictured above) in the 2 position to enable the recovery BIOS and restart the computer. This will let you boot the card without problems.
2. Boot into Windows/DOS prompt and get ready to flash the card - do not start the flashing process just yet.
3. Set the BIOS switch in the 1 position with the system running and ready to flash.
4. Flash your saved BIOS to the card.
5. Reboot, done.

The dual BIOS feature is just an added convenience for easier recovery, it is not a requirement for this kind of modding, nor is it evidence that AMD has planned their cards with unlocking in mind.

Test Results
Please report your findings in this thread (or e-mail me) so we can update the statistics. (Last updated Dec 27, 01:30 CET)

Manufacturer Cards
tested Unlocks and
works fine Unlocks but
rendering errors Does not
unlock
AMD 1 1 0 0
HIS 3 3 0 0
ASUS 1 1 0 0
PowerColor 1 1 0 0

[topgear]

if someone is interested they better hurry up coz amd is going to release new HD6950 which won't support this hack !

[vickybat]

A timed mod in my opinion.