How to fix bootloop after upgrading RAM to 16GB on MacBook Pro A1278 Mid 2010?

JFM_011 wrote:

I have a secondary laptop (MacBook Pro Mid 2010) it has 250GB HDD and 4GB RAM (now upgraded to the max aka 16GB) and since i upgraded it would boot to 10.6.3 and nothing else, not even 10.6.8 works as i have tested it, i did the combo update from 10.6.3 to 10.6.8 and it’s just stuck during boot now, so i am clean installing 10.6.3 onto an SD card as it was before (HDD is dying but i am not talking about that) 10.6.3 recognises all 16GB well. This MacBook has no battery as it has swelled and i disposed of it, here are the macOS/OS X/Mac OS X versions i have tested (it also sometimes just bootloops)

[Re-Titled by Moderator]

Original Title: I upgraded my RAM in my MacBook Pro A1278 Mid 2010 to 16GB and now it hangs on boot after trying to install past 10.6.3, how to fix?

First, if you are installing the full macOS onto an SD Card, I'm not sure how well that will work out since I'm not sure that will be fast enough. At the very least remove the internal HD since some drive failures can affect booting to external media.

Second, if the issue did not exist before the memory upgrade, then the memory upgrade is very likely the culprit. Macs are very picky about the memory they use, so it is best to only use memory from OWC since Crucial no longer provides Mac Compatible memory. Another possibility is you have a bad memory slot which is somewhat common on these older laptops....usually it will be the memory slot nearest the Bottom Case which develops cracked solder joints.