This is for 10.5.6.

I recently bought a 7600GS 512MB AGP card, and I was informed that all 7x00 series cards that had more than 256MB VRAM had issues in OS X that required flashing the ROM BIOS on the card.

Thanks to another member on InsanelyMac, the card is now working at FULL 512MB, with QE/CI+Rotation WITHOUT FLASHING THE BIOS! No more risking a bricked GFX card.

Here's how you can do it:

First, download these kexts and extract them to a safe location.

Make sure that you have UInstaller by ~pcwiz installed.

Next, make sure to go into your extensions folder ( /System/Library/Extensions ) and delete all Intel and ATI video drivers.

Using UInstaller, check the option to install kexts from HD, and then press browse and select all the kexts you downloaded from the link above, and then press install.

Next, delete Extensions.mkext in /System/Library and reboot, and at darwin, type -f.

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Mac OS X Leopard 10.5.8 (9L30) | Chameleon 2.0 RC3 | Intel Pentium 4 3Ghz 800Mhz FSB HyperThread 1MB L2 cache SSE3 1MB L2 cache works, cosmetic display of 512KB L2 cache | Asus P4V8X-MX VIA Chipset, VIA-VT8237 Southbridge | AC97 VIA8237 | Dual 1GB 333Mhz DDR SDRAM | nVidia PNY GeForce 7600GS 512MB 8x AGP DVI/TV-Out/VGA [NVinject 0.2.1; QE/CI/QuartzGL/Rotation] | Darwin Kernel Version 9.7.0: Sun Jun 14 20:48:28 IST 2009; Voodoo 2.0 Intel alpha3 :xnu-1228.12.14/BUILD/obj/RELEASE_I386 i386