Answer to "1333Mhz RAMs working on late 2009 unibody MacBook?"Hi, I have some interesting info. My MacBook late 2009 has bootrom MB61.00C8.B00 and I was UNABLE TO address more than 6 Gb (strangely enough 1 x 2 Gb 1066 + 1 x 4 Gb 1333). I work in a components store, so was able to try all kinds of modules (with differences in latency and clock speed). In other words, 8 Gb with my Mac turned out to be an impossibility. Then I had some issues with the Mac and I brought it to an Apple store for repair. They replaced the logic board. I still have bootrom MB61.00C8.B00, but now I CAN address 2 x 4 Gb (1066 as well as 1333 modules, while 1066 is seen by the system as 1066 and 1333 as - you guessed right - 1333 Mhz). Don't ask me why or how. Cheers, KNOKKi P.S. I used the same modules which formerly did not work, so differences in modules can be ruled out as a cause.