I recently upgraded my computer’s motherboard and processor, and spent the next few days trying to work out which glitches were hardware related and which were coincidental. One problem I had was that the GRUB bootloader menu would not appear when the computer started. It was clearly there. It would boot to the default operating system after 10 seconds. If I hit an arrow key it would stop and wait for me to choose an OS. It just didn’t show up. All I got was a black screen with a cursor in the upper left corner.
On top of that, when Linux started booting, the screen was messed up as if the character set had been run through a meat grinder. You could tell what the letters were, but there was a ton of extra garbage. Then, when init set the character set, the gibberish cleared up and the screen looked normal again.
I had been dealing with other problems that looked like video card or driver issues, but I eventually realized that the problem had nothing to do with the hardware upgrade.