Screen goes dark with "electrical" artifacts on the left side.

[mauricev]

I ran memtest on a MacBook Pro three times. I never got to see any memory errors because when I got to look at the computer, the screen was mostly black, with the exception of some electrical noise being displayed continually at the far left of the screen, particularly near the bottom. Not sure if was the result of bad memory being triggered or a problem with the CPU/motheboard.

[David (PassMark)]

Doesn't sound good.

There is a debug log file automatically written to the USB drive. So maybe there is something in that file.

[mauricev]

Somehow, I was using the pre-UEFI version. I am now using the current version and it passed two passes and certainly no black screen with noise. It sounds like the cause was a bug in the old version of MemTestx86 and this particular edition of Mac.