When I first got the 2007 Mac Pro, in 2009, I was running it in Mac OS 10.4.4.11 Tiger and Photoshop CS4 (11.0.0) would disable Open GL Rendering when it detected the stock nVidia GeForce 7300 GT card, which was on Adobe's list of unsupported graphics GPUs. So, I purchased a refurbished Apple Radeon X1900 XT. This card allowed Photoshop CS4 and Bridge CS4 to enable Open GL Rendering. Over the last year, the Radeon X1900 XT graphics card has been creating stripes on my screen when it is running hot and sometimes the dual displays would just shut off while I was working. Also, the computer was doing hardware freezes about once a day. This morning the Mac Pro shut down it's dual displays, while I was working, and I had to do another cold shut off in order to restart. I then manually shut the computer down and did a manual boot-up so that Snow Leopard would employ disk maintenance.
I shut the computer off and pulled the Radeon X1900 XT card and re-inserted the OEM Apple nVidia GeForce 7300 GT card. Now I'm running Mac OS 10.6.8 Snow Leopard with Photoshop CS4 (11.0.2) instead of Photoshop CS4 (11.0.0).
Now, the updated Photoshop CS4 under the newer OS, is enabling Open GL Rendering instead of disabling it. This graphics card's hardware limitation is now fixed so, I see no reason to buy the ATI Radeon HD 5770 Graphics Upgrade Kit for my Mac Pro:
Some who have purchased the Apple ATI Radeon HD 5770 say they still got the striping on their display when the Radeon HD 5770 card was running hot, just like with the Radeon X1900 XT.
So far, the OEM Apple nVidia GeForce 7300 GT is working fine and I'm not getting any striping on my displays with no display shut-offs or hardware freezes.
I'm glad to have Adobe's Open GL Rendering enabled with an OEM graphics GPU that runs cool and requires no imbedded cooling fan. Apples OEM nVidia GeForce 7300 GT, for the Mac Pro, is now actually on Adobe's updated list of supported GPUs for Open GL Rendering under Photoshop CS4, so why is it supported now? Is that just one of the benefits of the Photoshop CS4 11.0.2 update? It turns out that the card is supported by Adobe's Open GL Rendering in some limited ways as long as my Mac Pro is running an OS that is later than Mac OS 10.4.4.11 Tiger, like Leopard or Snow Leopard.
Maybe, some day, I will still need to upgrade to the ATI Radeon HD 5770 Graphics Upgrade Kit for my Mac Pro, especially if I upgrade to Photoshop CS5, because the old Radeon X1900 XT and the old nVidia GeForce 7300 GT is not supported in Photoshop CS5's OpenGL Rendering engine but the Radeon HD 5770 is.
The main net benefit of going back to the stock OEM Apple nVidia GeForce 7300 GTis that my Mac Pro is now "rock solid" and stable, running for weeks and months without freezing up or crashing.