hi i've prepared two mp 3.1 for a client, 2.8GHZ 32Go ram ssd, +sapphire radeon 280 model power connector 2x 6pin, mac efi rom made by netkas script, cinema display with dvi, but i find out some power cable issue: when i plug in one 666Y cable - mini 6pin to 2x 6 pin, the mac will not start, it give only one click on the psu position when you push the power button, and then nothing happened, it seems that the psu doesn't support the power of this card, but when i plug in another one 668Y cable - mini 6pin to 6pin and 6+2pin (of course we don't use the extra 2pin), it starts normally, since the cable came from the same factory, and nothing changed from other components, i guess there is lower power on the model 6+2pin than 6pin on Y cable, and the power consumption is lower, so it will start the video card with. this is no happenning on cmp 4.1 nor 5.1, anyone has the similar experience? hope this will help when met the same situation.