[monocasa]

In the 1960s, os compat was your problem as the end user too. There wasn't the strict divide between OS code and user code in the same way. The 360/91 that Tomasulo's algorithm originally shipped on didn't even have an MMU to separate your code from the kernel.

Additionally, compiler tech wasn't anywhere near where it was today, and high perf code was written in ASM. Therefore existing code would have to be rewritten to use more registers, but the 360/91 ran existing code just fine (which was very important for the 360/91's main customers).