Mac Pro 3.1 display shuts down

[Greyradish]

My Mac Pro display shuts down on me and goes into a kind of sleep mode but will not wake up, the monitor says there is no connection. This happens during playing video games or browsing the internet on both the mac and pc side. I thought it was the video card (gt 8800) so I bought a new card through apple (ati 4870), after installing the new card yesterday the problem came up again.

Model Name: Mac Pro
Model Identifier: MacPro3,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 2.8 GHz
Number Of Processors: 1
Total Number Of Cores: 4
L2 Cache: 12 MB
Memory: 8 GB
Bus Speed: 1.6 GHz

[MACUSER360]

same thing happens to me. I have a octo 2.8 with the 2600 video card happens more when i have 2 displays hooked up. but still happens with one too. the monitor says there is no connection. have to reboot to get it back. anyone have any ideas i thought video card but you switched yours out.

[nk747]

Signed up just to share the same problem, same mac pro (3,1) with a ATI Radeon HD 2600 XT graphics card, and often when i reboot no screen (need to reboot 5 times for screen to appear) , but shutdown keyboard shortcut works... so i am assuming it is the graphics card....????

Much welcomed would be a recomendation for a decent graphics card for my machine.
Model Identifier: MacPro3,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 2.8 GHz
Number Of Processors: 2
Total Number Of Cores: 8

thanks in advance

[Roman23]

I had this same machine.. except a 3.2 ghz with the radeon 4870 and I have never experienced any problems at all with my mac pro sleeping. Then again, I also have an Apple 24 inch cinema display.. Check to see if your 3rd party monitor supports or can handle wake from sleep which I am sure it can..

Other than that, check your usb 2.0 card to see if that is the culprit or maybe external drives hooked up might also be causing the problem.

[Roman23]

Model Name: Mac Pro
Model Identifier: MacPro3,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 3.2 GHz
Number Of Processors: 2
Total Number Of Cores: 8
L2 Cache: 12 MB
Memory: 48 GB - Yes, 8GB FBDIMMS are out at 800 mhz, and so are 16GB.
Bus Speed: 1.6 GHz
Graphics: Radeon 4870
USB 2.0 card by unknown - got on ebay from applemacanix.