I want to distance myself from the majority of this nonsense. Building a simple computer with a processor, a ROM, a full compliment of RAM, and a serial console interface is a 10-minute design and a 90-minute fabrication task. If it's designed to fit already existing firmware/software, it's even more or less practical to fit it into that firmware or software's understanding of what the hardware is that fits with it. That means that an operating system might be straighforward to accomplish in a day or two if there's software in the form of a decent monitor or OS to support it. HOWEVER, since there's little hardware support commonly applicable to both of the subject processors, let alone for a number of others, It's silly to consider anything but the simplest of hardware for a real-world implementation. I'm sure most people in any way familiar with the things we had to do back in the '70's will agree, that, from a hardware standpoint, building a single-board system with 64K SRAM, Whatever size of EPROM you like, overlapping it and disabled when copied into RAM, and a serial port is a no-brainer, requiring , as I previously said, about 90 minutes to wire-wrap. It might take longer if you have to find the parts. If you use a WD FDD/HDD card, it will take another 15 minutes to wire up the cable interface. If, however, you use just a WD1770 or 72 you have a floppy drive as well. For the Z-80,that means you have CP/M. I don't know what's comparable for 6502 development. If you simply stop after the serial console interface, say,a 16C450 off an obsolete but otherwise healthy PC serial board, you've got enough to run a decent debug monitor. I have a couple for the 6502, though I was wanting to incorporate the assembly/disassembly functions as well. That hasn't happened yet, and until I'm properly motivated, probably won't. Now I can't imagine why a graphics display, or anything so inane as that could creep into the consciousness of an otherwise perfectly sane person wishing to deal with one of life's fundamental mysteries, i.e. "which is really faster, the XXXX or the YYYY?" Dick -----Original Message----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Saturday, April 17, 1999 7:40 PM Subject: Re: z80 timing... 6502 timing