68K ISA project

From: "Ethan Dicks" <ethan.dicks at gmail.com> Sent: Tuesday, July 13, 2010 3:56 PM To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Subject: Re: 68K ISA project Cool !! Never heard of DTACK Grounded before, but I quickly read the first issue. Seems fun to read the others ... Probably known in this group, I am a fan of Motorola, not Intel. I learned assembler as first language on an M6800, build my own 6800, 6802, 6809 and finally designed and built a 68000 (which I upgraded later to 68010). In the end I am using a VME board with a 68020 at 30 MHz and RAM at 0 (!) "wait states" in my StarShip. Anyway ... More than 2 years ago, I started rewriting the 6809-based pdp8/e code to 68000. I "envisioned" a pdp8/e on a 68000 board with 8 fields RAM, two serial lines and simulated RX01 (using 3.5" floppy disk drives). I have actually translated the 6809 code to 68000 (making optimal use of all registers of course), but never tested it. I am sure it has bugs :-) I never returned to it due to the FPGA rush and the thought that the 68k code would be slower than a real pdp8/e. I am sure I have a 12 MHz 68k chip, and for some reason I also think to have a 16 MHz version, but I doubt Motorola ever made a 68k at 16 MHz ... Motoral chips have quite some margin in overclocking (I read somewhere). Would there be interest to run a (slow) pdp8/e on a 68k? I coded ASCII "art" for the lights display on a VT220 using ESC sequences. - Henk, PA8PDP