Before you get all "wrapped around the axle" with those SiLabs parts, give the Maxim/Dallas DS89C4x0 series a look. They're 5-volt one-clockers in the old standard DIP and PLCC pinout, so I use 'em as drop in replacements for the old Intel parts. They're LOTS faster and don't have all the expensive analog stuff that some parts use to justify their cost, not that that's a reason to ignore them.

These parts allow you to run much faster while maintaining compatibility with the external hardware (by using cycle-stretching, if needed). I use 'em for test fixtures, and other things where I need some performance.

These work fine for "keeping things running" or adding enhancements quite painlessly. They have 16 or 64 KB FLASH for code space and aon on-board 4KB XRAM, which can be mapped into either code or data space.

As with any 805x variant, there are some things you need to know about, so read the doc's!

RE