As I recall the "co-processor" slot on those boards was another CPU slot, with an extra pin; and when filled it took over and disabled the original CPU.

Edit: later 486SX may not have had FPU: https://retrocomputing.stackexchange.com/questions/12109/wer...

https://en.wikipedia.org/wiki/Product_binning#Semiconductor_...

http://www.os2museum.com/wp/lies-damn-lies-and-wikipedia/

My guess is that if there’s any truth to it that was early on before the process was fine-tuned. It’s hard to believe Intel would have tolerated a process producing that many errors since they could use the same die space to make more smaller chips.

intel used to sell cheap core solos back in the core duo days, which were just duos where one of the cores was faulty so they disabled it.

Same with the F model (no iGPU) chips today. People have done teardowns and found that more often than not its there on the die, just disabled because its faulty.

But you should have tried breeding on a 33 MHz 386SX. I think I had to let it run overnight.

My next computer was a Pentium 133. The difference in fish breeding was mind blowing.