GeoWorks was pretty cool on the 386 but GEOS on the Commodore 64 was just unreal -- it was slow and required some tedious disk swapping but even the idea of selectable, proportional fonts at different font sizes among its many other features was amazing on a 1MHz CPU, 64k RAM system.
I picked up my first C64 at a garage sale in the late 90s, and one of the disks it came with was GEOS. It really surprised me when it loaded and I realized what I was looking at.
The Game Boy has a Z80-like processor, though. Generally, Z80 instructions take more clock cycles to execute than 6502 instructions, so the clock speeds are not directly comparable.
