The 6502 was the very first microprocessor I ever programmed. Way back in 1978 I was working on an Apple II programming embedded applications on a “SuperKIM” 6502-based development board. All in assembly language, of course. Back then I wrote a fairly-well received assembler for the Apple II call “LISA: Lazer’s Interactive Symbolic Assembler.” I wrote lots of articles about the 6502 in various magazines of that era. Even wrote a book on the subject (see https:\/\/www.randallhyde.com\/AssemblyLanguage\/A2%20Hyde%206502%20Asm%20Lang.pdf)\u0010. Needless to say, I had invested a lot in the good old 6502.<\/p>\n\n\n\n
Then the Mac and PC came along. I stuck with the 65xx family up until the day the Apple \/\/ GS was finally put out to pasture by Apple (every now and then I dig my \/\/ GS out of storage and start it up; then immediately put it back when I’m reminded how slow it is). I haven’t written a line of 65xx code in over 30 years (as I write this). But there’s still a soft spot in my heart for that little old device.<\/p>\n\n\n\n
Every now and then I wonder “gee, how would I design a 65xx device today for an embedded system?” I’m not talking about building the latest and greatest 64-bit CPU, mind you, just something that would sit somewhere between an Atmel AVR and and ARM running on an Arduino-class SBC. <\/p>\n\n\n\n
Finally, I got bored enough with work that I decided to take the day off and work through the encoding for a 65xx-class machine. First, I thought I’d call it the 65020 (seemed like a cool play on the 6800->68000 and 68020 CPUs of years gone by). Naturally, somebody beat me to that name with their own little mind experiment. So I went with the more boring name of “65000.”<\/p>\n\n\n\n
Well, without further ado, here’s a link to the page I created for this mental toy:<\/p>\n\n\n\n