Identifying a defective RAM IC on laptops with soldered memory

Warning: some information in this article is uncertain and based onto third-party reverse engineering efforts. Official documentation from the memory controller manufacturer is required, however Intel does not make it public. This only shows the idea to narrow down the fault. Additionally, other factors such as a PCB or CPU fault could be the cause and not the RAM ICs themselves (e.g. common failure on MacBook Air 13" 2011 with board number 820-3023). Introduction We will take the MacBook Pro Late 2013 15" IG with board number 820-3662 as a case study, in its 16 GiB RAM configuration which means fully populated with the 32 RAM ICs. This specific logic board was not passing ASD EFI memory tests. Each RAM IC has a data bus with of 8 bits, so 8 ICs are needed for the full 64-bit width data bus found in modern PCs. On top of that, there are two memory channels and 2 ranks per channel for a total of 4×8=32 ICs. This also means that 1 data bit on the memory data bus has 4 associated ICs. ... Read full article.