Underclock/downclock/flash RAM (DDR) to ensure MacBook compatibilty (using free softwares)

Read FULL description for requirements and disclaimer.

DISCLAIMER: Flashing EEPROM of your RAM modules is not standard procedure and could possibly damage your ram. Do this at your own risk!!!
!! DO NOT ATTEMPT ANY MODIFICATIONS BEFORE YOU MADE A BACKUP OF CURRENT/ORIGINAL SPD EEPROM (use RWEverything to make a backup). !!

Using DDR3-1333 (or above) sticks on Apple equipped with Intel Core 2 Duo (Penryn) and Nvidia MCP79/MCP89 will not work. You'll get bip/flashing led light once power button is pressed and computer will not boot. You can bypass this by downclocking frequency of your ddr modules. So you can actually use your originally PC3-10600 (or above) sticks on your Macbook, which is hardware-limited to PC3-8500 because of the Nvidia chip. As long as you meet the requirements, you won't have to buy PC3-8500 only memory sticks/ram/modules since they are pricier than faster sticks (probably because of this Macbook "incompatibility").

This method was tested on a Macbook 7,1 (unibody white mid-2010 A1342, C2D P8600/GeForce 320M) and it should work with the Macbook Pro (A1278) aswell. Check the matching serial number of the RAM on both computer/every step as a proof that this method is 100% working. My Macbook runs two identical 4GB Kingstom memory modules, which were initially PC3-10600. I ONLY flashed one of these 2 sticks, the other one installed in the computer is still PC3-10600 but it is automatically underclocked during boot up to match specs of the slowest module. What could be worth checking is dual channel mode. I don't know if it is enabled, I'll check and if results are negative, I'll flash the second stick and check again.

You can ask any questions you have.

Required :
-Thaiphoon Burner (optional) : (free version should be enough as it is only used to check if memory is write-protected)
-CPU-Z (optional) : https://www.cpuid.com/softwares/cpu-z...
-RWEverything : http://rweverything.com/download/
-A Windows laptop (it is advised to NOT use VMWARE virtual machine on a Macbook to run these programs to flash your memory modules) with a SMBus that allows writing to EEPROM (I used an HP Elitebook 8560W, Sandy Bridge platform). From my understanding, Skylake and above WON'T ALLOW writing to EEPROM of memory modules.
-Obviously the memory module you want to use on the Macbook. I advise you to only install the memory stick you want to flash to avoid any confusion/mistakes. The memory module that was used in this video is the following : KINGSTON KTH-X3B/4G. It initially ran at 1333MHz (PC3-10600, CPU-Z reads PC3-10700 because it is an OEM module from HP). These sticks are 1.5V modules. 1.35V are suspected to cause issues (correct me if I'm wrong).

Before making any changes within SPD data array, make sure the SPD EEPROM chip is not write-protected. Please be aware that all of DDR3 SDRAM SO-DIMM modules manufactured by Samsung, Hynix, Elixir/Nanya Technology, Silicon Power, Crucial Technology (SO-DIMM), Patriot (SO-DIMM) and Micron Technology are shipped with enabled Permanent Software Write Protection (PSWP) feature that does not enable the SPD EEPROM chip to be reprogrammed. It is recommended to buy Kingston and Corsair DRAM modules since they should come with unprotected SPD EEPROMs. You should still check if the memory you plan to purchase and flash is unprotected before you buy it.

This method has been tested on DDR3. I guess it should work on all DDR revisions (as long as the program used recognizes the memory you plan to flash and that you fully met the requirements). You can use this method even if you don't plan on using your flashed modules on an Apple product, as the procedure is done under a Windows ecosystem.