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System will only boot with one 6950, not two, after windows/catalyst reinstall

Last response: in Graphics & Displays
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February 20, 2014 4:02:13 PM

I recently upgraded my hard drive, reinstalling windows at the same time. Previously, I had a pair of 6950s in crossfire that worked great.

- Installed Win7 x64 onto new HD - everything fine (two cards installed)

- Installed Catalyst - Windows refuses to load

- Removed second 6950 and crossfire bridge - system works fine again (with Catalyst this time)

- Attempted to reinstall second 6950 - windows refuses to load again

I know both cards are good since they were working this afternoon before I reinstalled everything. Help?
February 21, 2014 1:51:24 PM

What are you running for a power supply in the system?

You might also dive into the setting for ULPS in the registry and disable this feature, in case it's malfunctioning. To get at the setting for both cards, you may find that booting with the CrossFire bridge off works, then install the drivers, disable ULPS, and power down. Reinstall the bridge, and boot.
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February 21, 2014 1:55:47 PM

It's a 750w Silverstone unite (ST75F-P), so I think I should be good.

What's ULPS?

bigpinkdragon286 said:
What are you running for a power supply in the system?

You might also dive into the setting for ULPS in the registry and disable this feature, in case it's malfunctioning.


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February 21, 2014 4:28:50 PM

If you perform a Google search about ULPS you will find plenty of information about it. It stands for Ultra Low Power State, and essentially, it means in CrossFire configurations, AMD attempts to turn off any graphics card that is not the primary, until needed, but it can cause problems if you try and change a setting manually or when utilities try to access a powered down card. It's not a bad idea, but it's also not without it's problems, and disabling it may help you in your particular case.

ULPS is enabled, every time you reinstall AMD drivers, so if you need it off, remember you have to disable it after each driver install.
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February 21, 2014 10:21:40 PM

OK, just tried disabling ULPS via regedit after some Googling. Unfortunately, the problem persisted - when I reinstalled the second 6950, the system wouldn't load windows.
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