The KIM-1 User Manual, page one: "The KIM-1 is a Microcomputer Module." Then 100 pages of how to use it.

@hrh-6502.bsky.social these are the 6502 dyes I was talking about. Tiny things… would be nice to put one in a resin block for displaying.

Self-modifying code on the 6502 wasn't a hack. It was standard practice. The program rewrote itself at runtime to avoid slow indirect addressing.

New blog post - I've had this great idea to improve tape loading on the Minstrels, using a rather unexpected chip. blog.tynemouthsoftware.co.uk/2026/06/impr... Includes the neatest thing I have ever assembled on a breadboard. The new Minstrel 4th is now available to pre-order, shipping next week.

I apprenticed once with an arcade game repairman. His #1 trick was to slow down the CPU clock (various late 1970s processors). That and dusting all boards with a soft brush. And using a pencil eraser to clean edge connectors. And never completing a job in less than 2 hrs. #GOFAI

The 6502 in the Apple II ran at 1 MHz. No pipeline stalls, no cache misses, no branch prediction failures.

Commodore were a little too busy in-fighting in 1983 (Jack left in early 1984) to start a legal case that they might not have won. Also, it might have caused discovery that Motorola could have used against MOS after the 6501 lawsuit.

Commodore owned MOS Technology. They built the PET, VIC-20, and C64 using their own CPUs.

Had a nice chat with him at his store/lab when we were both a lot younger. AI was a noble endeavor back then, not a tragic psychosis. And the 6502 was a wonderland. #GOFAI #ComputationalThinking #Chess

The NES ran a modified 6502 - the Ricoh 2A03. Same instruction set, minus decimal mode.

Peter Jennings. Microchess. KIM-1. 1976. Playable chess in 1K of RAM.

A KIM-3B is a 8K bytes memory expansion made by MOS Technology (already part of Commodore then) for the KIM-4 motherboard. I recently acquired a good looking KIM-3B myself. Nothing new, all is already known about it. Now with photos made by myself!

New version of the KIM-1 Simulator coming: complete VT100 support in the console!

It is done! And is much more accurate now, thank you. elite.bbcelite.com/deep_dives/e...

Visual6502.org decapped an actual 6502 chip and photographed every transistor. You can watch each gate toggle, cycle by cycle, at the transistor level. No other processor has been this thoroughly exposed. visual6502.org

Squee!!! That is EXACTLY the model I first learned on! I wrote a 6502 assembler/disassembler for it in BASIC (just a bunch of read/data statements and peek/poke statements). I had so much fun programming that. I made a Battlestar Galactica video game for it (just character graphics but was fun!!).

PET 2001 emulator update: • Load hex-dumps (.hex, .hd, .dump) representing a prg format (with leading start address) in place of any binary files. • Improved support for local files (extensions .sav, .s, .local). Loading such a file triggers a user dialog to pick a local file. masswerk.at/pet

A 6502 based computer that uses a Raspberry Pico as a crazy powerful graphics card, and another as a ROM, file system, and monitor. It’s the Picocomputer.GitHub.io and it’s also less picky about resistor values than you might expect. It DOES get picky about USB storage > 8Gb though.

Various goings on on the island are, of course, inspired by Children of the Stones and The Prisoner, I'll leave you to spot those to avoid spoilers, sweetie. And the computers are back! The Kim-1 had at its heart the 6502 processor, hence grandad's book, door code and 'what a year 2056 will be...'

It was in the 80s, and I'd used Z80 for ages before getting access to a 6502. It just felt a bit different and odd from what I can remember.

6502 is like playing lego but with only one shape of brick. Z80 is like playing chess but with only knights.

Whatever else they do, they certainly keep emulator authors on their toes.

The magical art of storing data as sound. And back again.

The illegal opcodes on the NMOS 6502 were unintended side effects of incomplete instruction decoding. Some did useful things. Some did destructive things. Some did both. Programmers documented them all and used them anyway.

HomeComp HC-77B Emulator is live. A front-panel MOS 6502 single-board computer with emulator builds, ROM, docs, cassette support, launch extensions, adverts, wiki. GitHub/wiki: github.com/tmcd35/HomeC... First release: September 1977 Launch Next phase: Late 1977 — NIM Cassette #Mos6502 #EmuDev

The 6502 had 13 addressing modes. Each one a different way to point at memory. Immediate, zero page, absolute, indexed, indirect, pre-indexed indirect, post-indexed indirect. Learning them was like learning 13 ways to open the same door.

WDC's 65C816 extended the 6502 to 16-bit with a 24-bit address bus. It powered the Apple IIGS and the Super Nintendo. The 6502's DNA went from hobbyist boards to the most beloved game console of the '90s.

The 65C02 added the missing PHX/PLX and PHY/PLY, as well as several other useful OP Codes. I have been writing code specifically for the W65C02 recently, and I forget I can't use those when I go back to the stock 6502. TXA and PHA is still faster that pushing 16 bit register pairs though.....

Another project I've enjoyed seeing come together, next: the LT6502, @PaulaMaddox's homebrew MOS 6502-based BASIC-running laptop in a 3D-printed housing. https://www.hackster.io/news/paula-maddox-s-lt6502-is-the-compact-mos-6502-powered-netbook-from-your-80s-dreams-83838407732d #technology […]

HuC6280 Assembly programming for the PC Engine! (TurboGrafx-16) www.chibiakumas.com/6502/pcengin... #PCEngine #TurboGrafx #TurboDuo #NEC #HudsonSoft #homebrew #gamedev

This free app is fun for 6502 tinkering.

And it saved binary as two ASCII hex characters because that's how paper tape worked. Because of Jack's "spend nothing, anywhere, ever" mindset, Commodore kept the same tape format all the way to the 64

The KIM-1's cassette interface stored data as audio tones. You pressed PLAY and hoped. Tape speed, volume, and alignment all mattered. Saving your work was an act of faith. Loading it back was a miracle.

Steve Wozniak hand-assembled every byte of the Apple I monitor ROM. No assembler, no compiler. Just a legal pad, a pencil, and a reference card. The entire bootstrap was written by a human thinking in hex.

The 6502 overflow flag explained www.righto.com/2012/12/the-...

The 6502's decimal mode let it do BCD arithmetic natively. Most programmers never used it. The 65C02 fixed decimal mode's flag behavior. Most programmers still never used it. Some features exist to be documented, not deployed.

MS just open sourced 6502 Basic if you want an alternative

Also, you set sprite positions by telling the display chip (TIA) "now", a few pixels before the cathode ray was over that particular spot. No X/Y, all time-based, because there were no positional registers, just out-of-order linear feedback shift registers (LFSR) for counting pixels.

Since you're talking 6502 interrupts....... Something I've never really got around to understanding - why do 2600 programmers start with SEI? 6507 didn’t have interrupts. Did it achieve anything? Was it just cargo cult / comfort startup?

BRK on the 6502 was the software interrupt instruction. It was also what happened when your program hit uninitialised memory full of $00 bytes. Every 6502 crash was technically an interrupt request. Polite to the end.

New blog post - The first post in a series looking at improving tape loading future revisions of the Minstrel 2, 3 and 4th. blog.tynemouthsoftware.co.uk/2026/05/impr... See the end of the post for discounts on Tindie and Patreon that have both landed at the same time.

The 6502 powered the Atari 2600, which had 128 bytes of RAM. Not kilobytes. Bytes. The programmer had to update the display line by line, in real time, while the TV beam scanned. It was less programming, more juggling.

SYM-1 by Synertek was another KIM-1 competitor. Compatible enough to run KIM software, different enough to justify its own manual. The 6502 trainer market of the late '70s was surprisingly crowded.

I am told it is a bank holiday weekend. So why not have 10% off everything in my Tindie store - www.tindie.com/stores/tynem... DIY computer Kits and upgrades for ZX80, ZX81, Jupiter Ace, Commodore PET. Test tools, USB keyboard adapters, RC2014. Shipping worldwide, US orders with tariffs paid.

Hey is my computer gay enough? #kim-1 #commodore #mos6502

This is pretty trippy. Opcodes that the 6502 accidentally support: http://www.ffd2.com/fridge/docs/6502-NMOS.extra.opcodes They’re unintended consequences of combinations of pins. Some of them are useful. Only goes to show the strength of emergence through combinatorics.

The AIM-65 was Rockwell's answer to the KIM-1 - a 6502 trainer with a full keyboard and a 20-character alphanumeric display. It also had a built-in thermal printer. In 1978, that was luxury.

I'm still using assembly myself, I never got into C. For an idea of how far you can get with the venerable 6502, I've just finished writing a mini TLS library to go with the IP stack of the A2osX project. Granted it's 65c02 and requires 128Kb of RAM, but modern cryptography on a 40yo computer is 🔥

Charles I. Peddle (November 25, 1937 – December 15, 2019) was an American electrical engineer best known as the main designer of the MOS Technology 6502 microprocessor.

The 6502 wan't even meant for use in a general-purpose personal computer! It was optimised to be a smart peripheral controller. It just happened to have enough grunt to do the job anyway.