iATKOS | United Kingdom

Hi everyone, Im looking for a GPU to put in my mid 2011 21.5 inch iMac something preferably with the upmost of 4 gb of vram, does anyone know the absolute fastest gpu this iMac will support with 4gb of vram? the original gpu 6770m 512mb is insanely slow for me for my heavy needs, id prefer something that would be a direct ish fit im fine with modify the bracket to like be loose on one side, im using a ssd anyways so the issues with some opus needing to break off a bracket is fine with me, I just want the fastest gpu that works with its psu, cooling isn't an issue as ill be removing the optical drive so the fan goes directly to the heatsinks exhaust, and ill be making the temps lower with Macs fan control by changing fan speeds, im coming from the original GPU so once I install it on my already oclp sequoia, will it boot like show any image like I can log in to my os, I know that the original boot loader won't show cause of vbios, im just confirming that this gpu will be very fast for the iMac the fastest, and that ill be able to boot and rewrite oclp root patches for Nvidia Kepler or amd, I need metal, Thanks to the OCLP community!