Comment by cratermoon

> it takes 10 more units of work to distribute it across multiple computers.

That's just serialized work in a different form: in order for a computer to do a unit of work, it must be sent a unit of work. That's strictly serial -- a computer can't process a unit of work it doesn't have. So no matter how many units of work it takes to distribute the load, that's still 10 serial operations.

Amdahl wasn't only seeing things as separate chunks, with the parallelized work over one part of the code, and the serial work in a different part. The operations can be interleaved.