There already is a thread about Imac 2011 overclocking but it focusses more on the high end HD6970m. This thread is purely for HD6750 and HD6770 users. I´m a base 21" 2011 imac owner and this is my first mac. I used to be a pc builder/overclocker and gamer and i just want to know how much i can tweak my imac for gaming. The base frequencies of the HD6750m are 600/800Mhz and i got mine up to 800/1000Mhz respectively using the Sapphire TriXX tool. All on stock voltage with max temp lower then 80C and without increasing any fanspeeds. This represents a 33% overclock for the shaders and a 25% increase of memory frequency and should be noticable in gaming. It is also higher than the HD6770 stock speeds which i still don´t know the exact memory speed of? Is it 800 or 900Mhz not 1600 found on the net. Can anyone post the exact clockspeed? Preferably a Sapphire Trixx read out? I could not increase the shader speed anymore with the Sapphire TriXX tool but i have a feeling that there was more possible. Somewhere between 850 and 900 with a slight increase in core voltage. You can only increase the voltage by the TriXX tool with 0.05 volt which is around 5% and should be totaly safe. Would be interresting if you could increase the shader speed for the HD6770 above 800 because of its higher base clockspeed of 725Mhz???? Can anyone verify this????? Increasing the memory speed to 1050 caused for lockups (i hoped they would have gone all the way up to 1100 as the HD6970 does). I haven´t tried anything in between 1000 and 1050 because i don´t think it would make much of a difference. The memory chips used are hynix H5GQ1H24AFR T2L chips (i know this from the ifixit teardown) rated at 1.25Ghz @ 1.5v and 800Mhz @ 1.35v. It would be very interesting what voltage Apple is using, because this would probably hugely effect the overclocking possibilities and might explain why i could not reach 1050 Mhz.