>Anybody remember the 386sx? A firmware upgrade would have been kind of cool.

The main problem I saw with the 386SX was that it was made to be pin-compatible with the 286 -- which usually meant that systems built with it are likely to be "held back" by the motherboard and associated hardware (i.e. basically you couldn't expand beyond 286 capabilities in terms of memory and associated operation modes.). Of course it's not too different from 8088 (in that it was basically a 16-bit 8086 sitting on an 8-bit bus)...

And then there was the 80486SX... where it was essentially a 80486 with built-in numeric co-processor disabled. You could upgrade to get the numeric coprocessor by installing a 487 -- which was not just the coprocessor but a complete 486. However, you didn't end up with two 486s -- as the installation of the 487SX would disable the 486...