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The Mac I am using is an old , white plastic, Core 2 Duo version. The 'about this mac' section in OS/X says it's an 'Macbook 7,1' whatever that means and the Firmware (Namely EFI) is up to date.

I updated the Ram on the aforementioned Mac. It has 2 Slots which were occupied by 2 Samsung 1GB 1Rx8 PC3-8500S-07-10-ZZZ DDR3 So-Dimms.

For the Update I used 2 Samsung 2GB 2Rx8 PC3-10600S-09-10-F2 DDR3 So-Dimms.

After inserting the new Dimms the Laptop only emmitted a single beep, followed by a few seconds of silence and a beep again instead of starting up. Using both of the 1GB Dimms or 1 1GB Dimm and one 2GB Dimm, the laptop will start up just fine without issues. Actually the only combination which does not work is either a single 2GB Dimm or 2 2GB dimms together.

Now I've come across a few posts which said that the RAM-Controller tries to use the faster RAM with the higher Speed saved in their SPD which leads to the error, because the board, the cpu or whatever part of the mac doesn't support that.

I also have the suspicion that the 2Rx8, instead of 1Rx8, on the label of the 2GB Ram could spell some compatibility issues.

I've read that this means double ranked Ram instead of single ranked ram. The new Modules have 8 Packages on either side, while the old ones only had 4, which is supposed to be an indicator for 'double rankedness', apart from the suspicious label as well.

While 1x1GB and 1x 2GB works, it is definitely not the desired result of my upgrade.

Therefore my question:

First of all, what do you think produces this error? The higher speed, or the supposed double rankedness of the new ram, or some other, yet unmentioned compatibility issue?

In the case of double rank vs single rank there shouldn't be anything I can do. However if the higher speed is the issue then I'd consider trying to flash the SPD of the RAM Modules, if in fact there is no way of forcing the mac to use a lower speed.

Therefore, do you know if there is a way to force the MAC to use the faster 1333 MHz Ram with only 1066 Mhz clock speed apart from flashing the ram?

Thanks for the help in advance.

PS: The 3GB when I mix the modules are shown in the OS without problem and are supposedly uses by the System.

Also, I don't think it actually matters, but I am using bootcamp with Windows 7 x64.

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