Why does this work

[Mattster503]

So i have a IMac early 2009 2.66 Ghz

and the ram is locked at 1066 ddr3 ram but i stuck 2x2gb sticks in the imac 1333MHz and it worked and booted and not noticing any issues i had another imac like this not too long ago and when i tried it... it just beeped.....  but this time when i put the ram in it booted i was so suprised 

heres a screenshotAs you see its working

 

[corrado33]

The motherboard determines max RAM speed.

 

It's likely that your Mac was offered with 1333 MHz ram in a higher config. Or simply that the motherboard supports that ram and your other one didn't. 

[Mattster503]

Just now, corrado33 said:

The motherboard determines max RAM speed.

 

It's likely that your Mac was offered with 1333 MHz ram in a higher config. Or simply that the motherboard supports that ram and your other one didn't. 

its the same imac as before though 

 

[corrado33]

Just now, Mattster503 said:

its the same imac as before though 

 

Likely an updated motherboard? Lots of revisions for computer motherboards. Or the first time you installed it wrong.