<Allison wrote: <> I'd start with a 32bit PDP-8 (just add 20 more bits on the right side). <and in another posting: <> Me I'd do a stretch-8 for fun. though yours sounds interesting too. < <A Stretch-8 would require too much time spent on hacking -8 software for m <taste. Why not just build the equivalent of one of the DEC 18-bit family <members (PDP-4, -7, -9, or -15), since the PDP-5 and -8 are basically a 12- <version of the PDP-4. Then your project is at least compatible with <something, and can run some existing software (operating system, macro <assembler, Fortran). Several reasons. Don't know the 18 bit machines at all. I would want a machine that would fit in nx4 or nx8 format parts. I'd want a really simple instruction set as that simplifies the hardware ruling out the 10, 11 and vax. So streatching an 8 is it. Now a stretch-8 would have software as the bits added would only impact the address field. Makeing the top 5 bits and the bottom 7 behave as the normal 8 would make code port fairly reasonable. I've always found the 8 limiting in only one way, address space. Basically the Nova is a similar idea stopping at 16 bits. Allison