The IBM WorkPad z50 is a NEC VR4121 based PDA. It comes with WinCE in ROM.
- 131Mhz NEC VR4121 SoC
- NEC VR4171A Companion chip
- 16MB RAM (Expandable to 48MB)
- 4MB Video RAM
- 20MB ROM
- ITE IT8181F Video controller (datasheet part 1 and part 2)
- Rockwell RP336LD Modem
Linux-VR is rumored to work on the z50.
There is a netbsd (http://netbsd.org/Ports/hpcmips/) port available.
Useful info and datasheets on various parts used in this machine can be found at http://www.eecg.toronto.edu/~lemieux/z50/