Can't Remeber - Man Gains Ability to do so many tasks at once that his head explodes

[Lawnmower Man]

THis was a story my grandfather talked about before he died and I want ot try to find out what it was. Some guy is developing the ability to do an increasing number of simultaneous task, but when he tries to add on just one more, his head explodes. I'm not sure, but I think that the straw that broke the camels back was a mundane one, namely makeing a piece of toast.