Not just "really back in the day", but even as late as "only a few years ago" (meaning 15-20 years), every time I started my PC, it would slowly "count through" the installed RAM, apparently doing some sort of check/verification.
This caused painfully slow boot times for seemingly no good reason.
But it was possible (perhaps only after year 1998 or something?) to turn this off in the BIOS settings, and then the computer started much faster.
It seems like a pointless and frustrating default, causing everyone except for "super-nerds" (those who ever looked into the BIOS settings) to believe that PCs were extremely sluggish and cumbersome to boot up.
Why did they do this "test"? If there were some error with the RAM (which never once happened to me on any PC I ever used), would it just refuse to boot? Wouldn't I notice this anyway while using it? I don't understand the basic purpose of doing this "diagnostics test" on every single boot, especially since it was apparently only performed on the RAM and no other part of the system.