New blog post - A VIC20 S-Video conversion: blog.tynemouthsoftware.co.uk/2026/04/vic2... A simple (and reversible) mod with pretty decent results on CRT and LCD monitors and even USB capture. (at least with this VIC20, and with the monitors I tried)

There are exactly 13 addressing modes on the 6502. Sounds like a lot until you realize "absolute indexed indirect" means the CPU does three memory reads before it even knows where your data is. And it still finishes in 6 cycles.

If you’re in the Seattle area in May..

The Apple 1 was released in April 1976. It did, of course, have a 6502. Apple sold computers based on the 6502 for the next 12+ years. Which is kinda crazy.

The KIM-1 Programmer’s Guide to the MOS 6502 https://setsideb.com/the-kim-1-programmers-guide-to-the-mos-6502/ #6502# assembly# KIM-1# MachineCode

The KIM-1 Programmer’s Guide to the MOS 6502 The KIM-1, 50 years old as of 2026, was the first 6502-based home computer, designed by the legendary Chuck Peddle and sold by MOS Technologies themselves. (Well, we're not sure if the Apple I or the KIM-1 was first. Or maybe it was the JOLT? As I've […]

The Apple II's disk controller used only 8 chips. Woz replaced the usual 50+ with clever software on the 6502. The hardware engineers said it couldn't be done. The 6502 said hold my clock crystal.

The 6502's decimal mode flag persists after interrupts on the NMOS version. So if an IRQ fires while you're in BCD mode, your interrupt handler does BCD math by accident. The 65C02 fixed this by clearing D on interrupt. Only took a decade.

#ComputationalThinking is the key skill of the 1975-2035 epoch; quite literally existential. My contributions are mainly in the #CitizenScience, #Forth, and #GOFAI realms. But for clear, deep insight into human-machine early psychology, read www.salon.com/2006/09/14/b... by @davidbrin.bsky.social

The KIM-1 manual was written so clearly that teenagers in 1976 taught themselves machine language from it. No YouTube. No Stack Overflow. Just a spiral-bound manual and stubbornness. MOS Technology didn't just sell hardware - they sold literacy.

Bill Mensch at #VCFEast whova.com/web/GHMfP@@J...

The 6502 reads memory on every single clock cycle — there's no idle bus. Even when it doesn't need data, it fetches anyway and throws it away. The bus never sleeps. Engineers call it “transparent.” I call it overachieving.

Second Revision of 6502 Laptop Discussion | hackernews | Author: uticus

DeiMOS – A Superoptimizer for the MOS 6502 https://aransentin.github.io/deimos/

Ever wonder how 6 tiny LEDs could tell you everything? 🔴 MICRO 6502 Journal #49 (Jun '82) dives deep into the KIM-1's display hardware — the hex digits that made debugging feel like magic. Read it free on Archive.org! https://archive.org/details/micro-6502-journal-49

wow. wow. i can't believe my friends are slandering the MOS Technology 6502 in MY DMs. what has the world come to

Virtual KIM got updated. Improved 6502 lessons and a new ROM that might look familiar to Apple ][ users. apps.apple.com/us/app/virtu...

Update for “Opcodes” app is out! I fixed some missing 68000 instructions, improved the view on the iPad, and now you can paste in a string of hex digits to disassemble them in the scratchpad. apps.apple.com/us/app/opcod...

Commodore's Peter Jennings wrote Microchess for the KIM-1 in 1976. A complete chess program in 924 bytes. Not kilobytes. Bytes. Today a web page cookie is bigger than an entire chess engine.

The biggest story in the world right now is that the president of the United States is a demented old man who takes pleasure in torturing and killing people and is committing crimes with impunity. And yet most legacy media outlets are too cowardly to tell it like it is.

New blog post - Roller Bearing IC Leg Straighteners: blog.tynemouthsoftware.co.uk/2026/04/roll... I have been after one of these for ages and accidentally bought a second one whilst looking for parts to improve the first.

Ever wish you could step through your code one instruction at a time? In 1982, MICRO Journal showed how to mod your KIM-1 for single-step debugging. Hardware hacking at its finest! 🔧 archive.org/details/micro-6502-journal-44

The KIM-1's cassette interface stored data as audio tones at 22 bytes per second. Loading a 1K program took 45 seconds of patience and faith. You pressed play and hoped. It was basically prayer with a tape deck.

White KIM-1 cleanup This one is a Rev D with a ‘white’ PCB. The KIM-1 is working. The keyboard handmade@. With the DIY keypad method based upon the work of Eduardo Casino and Pete (peo2000)I replaced the keyboard Wires removed clean with alcohol and a brush this KIM-1 may join my collection

More on my website: retro.hansotten.nl/6502-sbc/kim...

In the #lounge waiting for the plane to #revision2026 #demoparty #6502 #commodore64

New video: "Relatively Indirect". The intro painting is "The Love Letter" by Johannes Vermeer (1669) In today's episode, I implement 2 of the 12 addressing modes that the 6502 CPU provides. Along the way I make the silliest programming mistake possible. www.youtube.com/watch?v=qc3S...

If you’re a 6502 fan, this free iOS app includes a bunch of 6502 data, an assembler and more. Just saying. apps.apple.com/us/app/opcod...

🔧 Early KIM-1 boards had a different crystal oscillator than later production units. MICRO 6502 Journal #40 (Sep 1981) shows you exactly how to upgrade it! https://archive.org/details/micro-6502-journal-40

Reminder! VCF PNW in Seattle is coming up. I'll be one of the exhibitors, so if you're in the area, please come and say hi and stay for the retro goodness.

On this day in 1980, Microsoft announced their very first hardware product: the Z-80 SoftCard for the Apple II.

Bill Mensch's 65C02 fixed the indirect jump bug, added new addressing modes, and used CMOS so it drew almost no power when halted. The WDC 65C02 is still in production today. Fifty years and counting. Try getting support for a five-year-old JavaScript framework.

The April 1976 issue of BYTE magazine saw the first mention (and advertisement) for the KIM-1 single board computer from MOS, aka the best known 6502 dev system. The 6502 CPU made so many things possible - including Apple Computer.. Happy 50th Birthday, KIM-1!

Looks good, 16K and BASIC 4, so _should_ be OK with an SD2PET. Interestingly remarked 6502. I guess they didn't know Commodore did the dates the other way around, so that would be 18th week of 1937. or maybe it slipped through a wormhole from 2037?

My own article gave me an idea on how to optimize the 6502 16-bit multiplication with 28% speed-up, and the calling code speed is enhanced as well. Available in the CVBasic repository github.com/nanochess/CV...

Indeed! The 6502 is extremely efficient clock for clock, but beyond that BBC Basic is super fast for an interpreted basic. The 2Mhz Beeb is just slightly faster than a 4.77Mhz IBM PC 5150 running also BBC Basic. I should run this on my Electron to see how terribly slow that is. 😂

The 2nd part of the series 'How to Write Machine Code Game' was published 41 years ago in the March 1985 issue of The Micro User. In this article I explained Exclusive OR ( EOR ) and how to use it to plot, and erase, software sprites on a BBC Micro. It used 6502 machine code for performance reasons.

Apple turns 50 today. Here is the entire Operating System for their first product: the Apple I. It's 256 bytes of 6502 code now called the WozMon (Wozniak Monitor). It lets you enter code for your own apps and run them. It provides APIs for console output, keyboard input, and ending an app.

In celebration of Apple's 50th anniversary, I'm offering 10% off my shirts with the MOS 6502 - the chip that powered the Apple I (and II and so many others of that time). No joke. And just today: April 1st, 2026. Code: APPLE50YEARS greyandslate.com?coupon=APPLE... #retrocomputing #mos #apple

6o6 v1.1: Faster 6502-on-6502 virtualization for a C64/Apple II Apple-1 emulator http://oldvcr.blogspot.com/2026/03/6o6-v11-faster-6502-on-6502.html

What if... we had Prince of Arabia on the Acorn Electron. This is what it could look like. Only problem: there are A LOT of graphics in this game 🧐 Shout out to the team that made PoA on the Arduboy github.com/Press-Play-O...

🎵 Making music with a KIM-1! In Apr 1981, MICRO journal showed how to generate square wave PL tones from a single-board computer. Who needs a synth when you've got a 6502? 🎶 https://archive.org/details/micro-6502-journal-35

Best of MICRO here: retro.hansotten.nl/6502-sbc/kim... and the whole archive here: micro.applearchives.com

While we do have a real Altair 8800 that we demo, we’re working on our next workshop which will be to build a Altair 8800 replica and learn how to use it. We’ll announce the date for this at VCFPNW next month! icm.museum #kit #retrocomputing #vintagecomputing

Floppy disks on a KIM-1? In Nov 1980, MICRO Journal showed how to hook up a Percom drive to your single-board computer. Storage upgrade! 💾🔥 archive.org/details/micro-6502-journal-30

Are there any other paper-based magazines related to 6502 computers still being published? Https://juiced.gs

It's a "reverse borrow" flag. I think of the SEC as putting a borrow bit on the shelf in case it's needed. If it's still there when you're done, there wasn't a borrow.

Used to catch me out. Z80’s ADC and SBC work as you’d expect. The in-house 6502 assemblers at Software Creations had pseudo instructions for ADD and SUB that did CLC : ADC and SEC : SBC.

The carry flag on the 6502 works backwards from what you'd expect. SBC requires you to SET carry before subtracting. Every beginner forgets this exactly once. Then never again. Pain is an excellent teacher.