AMD Radeon HD 6770M (512MB) displays/uses incorrect VRAM amount of 229MB under Windows 7

Hello all,

I am new to this community and will try to keep my post brief as possible, however this is a seemingly complicated issue.

I have had my mid-2011 model iMac since July 2012 and as a crossover from years of Windows-based PC use have always had a Boot Camp partition handy for gaming (mainly single-player and online RPG games that require a fair amount of VRAM). I have been dual-booting for months now and have had no issues.

Now, my iMac has 8GB of DDR3 RAM inside of it, however, upon installing Windows 7 I accidentally installed the 32-bit version of the OS as well as whatever drivers are included by default in Apple's Boot Camp support software for Windows 7. This worked fine for my purposes for quite some time, however by installing the 32-bit version, especially with RAM-hungry Windows, I was effectively limited to using under 4GB of RAM in contrast to the 8GB my system has and is avaliable to me while running OS X.

Today I decided I was fed up with not having access to the RAM I paid for and I desired a performance boost as I ventured to the more graphically intense areas of World of Warcraft. I removed the Windows partition using the Boot Camp Manager in OS X and then reinstalled the 64-bit incarnation of Windows 7.

As I said previously, I essentially use Boot Camp only for gaming, so you can imagine how dismayed I was when I started up WoW expecting significantly improved performance only to experience worse graphical performance than ever before (despite the game detecting more memory and reccommending higher settings!! xD). The game provided about 45fps consistantly in the area I'm in on the 32-bit version with (presumably) 32-bit drivers and had now dipped to about 25-30fps under the 64-bit environment. This does not look very great running at 1920x1080 resolution on the iMac's screen. =(

Upon looking into the cause of the nonsensical drop in performance, a quick Direct X Diagnostic test revealed to me that the system is only detecting/using a mere 229MB of the avaliable 512MB of my graphics card. Upon furher research, I also realized that the driver included by default for the 6770M in Apple's Boot Camp support software is woefully outdated.

Assuming an outdated driver to be the culprit, I immidiately began searching for the newest driver from AMD, and, after going up against countless roadblocks to updating my driver, (messages from Catalyst Installer saying I "do not have a proper video adapter", etc.) I located and installed what I believe to be the most updated version of the driver (9.002). However, even with the latest driver update installed, the system still detects only 229MB of avaliable video memory and in-game performance is still inferior compared to what I experienced on the 32-bit version of Windows. 😟

I also feel it is worth noting that back when I was running the 32-bit version, a DirectX Diagnostic would tell me I had over 1000MB video RAM (something like 1240MB, but I cannot be sure). The system definitely performed like it had 512MB, however. Seeing as performace was unaffected, I ignored this error. This may be irrelevant but I don't know, so I'm including this bit of information just in case.

I am completely lost at this point and am looking to you for help.

Thanks in advance for any help I may receive and let me know if there is any further information I can provide! 🙂

EDIT: I would just like to clarify that my QUESTION is: How do I improve my graphical performance without reverting to the less memory-efficient 32-bit version of Windows 7? Thank you.

Message was edited by: broke_gamer56