Although this does not have to do directly with 6502 projects, I'm including my HP-41cx hand-held computer, and further down, the HP-71, because of all the inspiration these have given me for my 6502 projects. Both have expandable operating systems, file chains in non-volatile RAM, expansion ports, the interface loop (HP-IL), and tons of other features that serve as outstanding models of engineering. The LCD here says, "INPUT: -7.2dBV"

This is the top end of the HP-41cx, showing the four ports. I had a friend scan the picture and I'm a little disappointed that the scan took away so much detail in the dark area. I have the ZENROM module in one port (for synthetic and assembly-language programming), the Advantage module in another (with a long list of math functions), and in a third port, the interface loop as well as the Extended I/O module which I had built into it so I wouldn't run out of ports. One port is still empty. I wish I had gotten a large RAM for it when they were available. The 41cx is like a 41cv with built-in time module, extended functions, some extended memory, text editor, and some other things not available on the 41cv.

I have the IEEE-488 interface converter for HP-IL, which I used with this computer to control a rack of equipment in the late 80's at a little company where I worked. This controlled the production testing of the first $2,000,000 of a particular product we made. Then it was replaced with an HP-9000-series computer with a 68000 processor.

What attracted me so strongly about these little computers was the extreme portability and their capabilities in data acquisition and control. I kept thinking I would like to make a computer resembling these, using a 65c02. Why? Weren't these HPs adequate? Actually, they are extremely sophisticated, even in their I/O; but when microsecond control of lots of individual I/O bits is important, something else is needed.

This is the HP-71-- far more powerful than the HP-41. It has by far the best BASIC I've ever seen (occupying about 200KB, mostly in ROM) but a rather poor implementation of Forth. This is where I originally learned Forth. I've never used the assembler for it, but I do have, and use, a lot of very efficient BASIC extensions written in assembly by the users' groups. This computer has four ports in the front, plus the HP-IL port in the back on the left, and the card reader port at the top right where I instead have an extra 96KB of RAM. Card-reader-port RAM modules were available with up to 160KB, but I got all I could afford at the time. There have been a few times it would have been nice to have more. I do have another 64KB of extra RAM in one of the front ports.

So what would be the chances of being able to build a portable co