I was just thinking 4.77MHz because a lot of the games on the IBM PC/XT time weren't controlled by anything besides CPU speed so they ran at light speed once MHz started to increase. I thought turning turbo off tried to re-emulate that speed to make those programs work correctly again. I might just be confusing that with an old DOS utility that use to do the same thing.
"Forces act when not restrained" - Puckdropper