I just updated my iMac to Lion 10.7.4 and now my GPU available RAM is not being reported correctly.
The machine is a mid 2011 unit with AMD Radeon HD 6970M graphics card with 2048 MB (2GB) RAM onboard, the default RAM was 1GB.
After the upgrade I noticed on iStat menus that the GPU Memory Usage was being reported as 100%, on a freshly booted machine with 2GB of video RAM that obviously was not likely.
After some investigation I ran the Apple 'OpenGL Driver Monitor' utility from the developer tools. It reported the 'Current Free Video Memory' Max memory was minus 2,075,377,152 bytes (screenshot 1). Uh huh. The current memory reported was similar, a negative number.
I then ran a graphics program that utilises the GPU and the current memory immediately changed to positive 1,846,786,048 bytes as shown in screenshot 1.
More damning is what is seen if the utility is run in tabular mode, the free memory number is wildly wrong and shows an amount so... well let's just say I wouldn't say no to that much GPU video RAM. The wild number change is the point at which I ran the graphics program.
Seems pretty obvious to me that the 10.7.4 update has introduced a bug in this area. Anyone else finding this? If you don't have 'OpenGL Driver Monitor' app you can get it from free Apple Developer Tools (big install though) or you could download free trial of iStat Menus from Bjango. If GPU memory usage shows 100% (after reboot and not running any applications) on your Mac running 10.7.4 then you have same problem.
The wrong number reporting is one annoying thing, bigger concern is whether some applications will query the OS and get a wrong free memory reading and not run because of it.