Undervolt Powercolor 6850 SCS3

[strangerranger]

Dear Experts!

For the passively cooled 6850 SCS3 it would be most desirable to undervolt. But when I change any voltage via RBE1.28, I get BSOD after reboot.
So far I found no tool to undervolt this card, but TRIXX can overvolt it so it might by possible.

Is this problem caused by this particular card or something you already came across?
I attached the original (unmodified) bios file. Maybe there is something wrong with the way RBE interprets the bios settings?

Cheers,
strangerranger

 

[strangerranger]

Update:

Changing any of the clock settings via RBE results in BSOD when booting windows (i guess that is to be expected due to AMD drivers).
Changing voltage settings via RBE results in BSOD.

I can change the fan settings via RBE without triggering BSOD => modifying the bios and flashing works

Neither RBE nor its hex dump shows selectable voltages / voltage registers. Perhaps if someone has an idea where to look for voltage values in the hex dump I could try to modify those?

Suggestions welcome!

Cheers,
strangerranger

 

[erocker]

Have you tried uninstalling your drivers before you flash? This may take care of the BSOD problem.

 

[strangerranger]

I tried this:
1) uninstalled driver
2) changed voltage in 6850 bios
3) reboot - no BSOD
4) installed driver - reboot - BSOD

From reading the RBE tutorial it did not become absolutely clear to me how this bluescreen comes about. Does the driver compare the bios settings to the values expected from the bios signature?

 

[strangerranger]

Update:

Changing bios settings without a driver being installed does not seem to change the clock/voltage settings. Here is what I did:

1) Uninstalled drivers (system settings - express uninstall)
2) Changed bios settings: clock info 01 (100MHz/150MHz/0.95V) to (200MHz/300MHz/1.1V). This seems to be the idle mode (since I can not test performance mode without drivers).
3) Reboot without drivers
4) GPUZ sensors still read the unchanged values: (100MHz/150MHz/0.95V)
5) Acquired bios: the new values (200MHz/300MHz/1.1V) are still there but do not seem to have any effect.

After this I would suspect that there is an issue between RBE and the 6850 SCS3.
Or did I do something wrong?

Cheers,
strangerranger

 

[strangerranger]

I found a way to change both clocks and vCore: "Ati Tray Tools".
After uninstalling CCC (and deactivating AMD polling), I was able to set the low power state 150MHz/300MHz/0.95V as well as the standard-clocks at reduced vCore: 775/1000/0.95V.
It is stable and considerably reduces the heat load:
-20 Watts in idle
-40 Watts under load

Under these conditions, the 6850 SCS3 might provide the best FPS/Watt on the market while being completely passive.

I still have no idea why changing vCore in the bios produces a bluescreen or why the standard clock in idle mode is 250/1000/0.95V, but at least I have a working solution for my system now.

Cheers,
strangerranger

 

[dejjin]

You are getting BSOD after reboot, I don’t have a proper answer for it. May be it can cause because of AMD drivers. Do one more thing; try uninstalling your drivers before you flash. And see if dell 5110cn is working fine. If the first one doesn’t work then definitely the second one will help you to solve all your issues. Don’t forget to update us with the latest status. I would like to hear how you managed to come out from this trouble.

 

[strangerranger]

Hi dejjin

If I interpret your post correctly, I already did what you suggested:

I tried this:
1) uninstalled driver
2) changed voltage in 6850 bios
3) reboot - no BSOD
4) installed driver - reboot - BSOD

According to powercolors tech support, AMD drivers check if the clock settings are correct,
but not if the voltage is set to the standard values. So I don´t see the reason for the BSOD.