Can my iMac Early 2009 (20") supports 1333Mhz or 1600Mhz RAM?

What will be the consequences if I install a 1333MHz or 1600Mhz ?

Using the 1333 MHz modules will likely work without issues, but the 1600 MHz can be a bit squirrelly. The issue is not so much the modules rated speed it's the RAS & CAS of the discreet memory cells.

Think of it this way... You have a three-legged race and one of the teams has one person with a dead leg that is bound to the other person. So they are able to get to the finish-line doubly quick. So the race is over before anyone else gets across and everyone walks away so no one see's who came in second.

This is similar to what happens here as the amount of time the memory is read is so long the setting of the cell gets lost so the value returned is not correct.

Bottomline here is stick with the correct RAM and its cheaper besides!

sorry only 1066 works no 1333 and 1600 i have the same problem today