[jks]

PETSCII? On the Commodore 64 you could press the Commodore key and Shift together to change character sets between lowercase and the graphical characters.

But the Unix login thing might have been because of teletypes? https://www.columbia.edu/cu/computinghistory/teletype/ claims that ASR 33 used 8-bit ASCII but was uppercase only - not sure if the "8-bit" claim can be true.

On some Unix (and Linux) systems, you can still enter a kind of retro mode with "stty olcuc iuclc" (output lowercase to uppercase, input uppercase to lowercase) and turning on Caps Lock.