Last Updated: September 27, 2021
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programmatically downclock speed of SO-DIMM DDR (Macbook, EFI)

I had to temporarily move to the old model of a Macbook [http://www.everymac.com/systems/apple/macbook_pro/specs/macbook-pro-core-2-duo-2.4-aluminum-13-mid-2010-unibody-specs.html], so I decided to add some RAM (2 modules - 4Gb DDR3 1333Mhz).

Know what? Macbook EFI doesn’t automatically downclock speed from 1333 Mhz to 1066 Mhz for SODIMM DDR3. So, you can do it by yourself as I just do.
damn marketing, what could be easier than the automatic lowering of the frequency by EFI.

Macbook Pro 13 Mid'2010 will not boot with the 1333Mhz memory (if you insert two modules by 4GB each with 1333Mhz). You can use old (1066Mhz) and new (1333Mhz) memory and it'll work because old memory is working on 1066Mhz and EFI automatically downclock the new one to this speed. damn marketing.

I could just go and replace the memory, but it is too easy.
Hard way:
- buy (buy! don't turn on torrent) Thaiphoon Burner http://www.softnology.biz/;
- install Windows (9x/NT/XP/2003/x64/Vista/7) via Boot Camp or find computer with preinstalled;
- insert your SODIMM 4GB with 1333Mhz, reboot to Windows and start Thaiphoon Burner.

Just completed 99% of work. Next steps:
- select your SODIMM via "Read" button of Thaiphoon Burner;
- create backup of SPD;
- then press "Editor" and change “Min SDRAM Cycle Time" from 12 to 15 and Clock Freq changes from 666.67 (1333 Mhz) to 533.33 (1066Mhz);
- write your change to SPD on the SODIMM;
-+ delete Boot Camp partition from your Macbook (optional).

And now I have one module with 1066Mhz freq, so EFI just downclock another module to 1066Mhz automatically. Just works.

A small victory over big... Dash it, just buy a unit with 1066Mhz frequency.