KIM-1 @kim-6502.bsky.social

The KIM-1 and classic 6502 related topics. Zero page FTW!

New update to Virtual KIM includes programming lessons in 6502 with a built-in assembler to try your code as you go. Somehow this is still free.

apps.apple.com/us/app/virtualkim-6502-emulator/id1548356829
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New blog post - A VIC20 S-Video conversion:
blog.tynemouthsoftware.co.uk/2026/04/vic20-s-video-conversion.html
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)
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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.
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If you’re in the Seattle area in May..
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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.
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The KIM-1 Programmer’s Guide to the MOS 6502 setsideb.com/the-kim-1-programmers-guide-to-the-mos-6502/ #6502 #assembly #KIM-1 #MachineCode
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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 […]
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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.
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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.
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Manuals..
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Reposted by KIM-1
scidata.ca's profile picture
Michael Will 🍁 @scidata.ca
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#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/basic_2/
by @davidbrin.bsky.social
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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.
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Bill Mensch at #VCFEast

whova.com/web/GHMfP href="/profile/@JlCnOF3xlEWLmBBm1POMpM3REEcBH@BfF1SA=/">@@JlCnOF3xlEWLmBBm1POMpM3REEcBH@BfF1SA=/
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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.
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Reposted by KIM-1
news.karthihegde.dev's profile picture
Cartero @news.karthihegde.dev
5d
Second Revision of 6502 Laptop
news.ycombinator.com/item?id=47626242 | hackernews | Author: uticus
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DeiMOS – A Superoptimizer for the MOS 6502

aransentin.github.io/deimos/
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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! archive.org/details/micro-6502-journal-49
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wow. wow. i can't believe my friends are slandering the MOS Technology 6502 in MY DMs. what has the world come to
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Virtual KIM got updated. Improved 6502 lessons and a new ROM that might look familiar to Apple ][ users.

apps.apple.com/us/app/virtualkim-6502-emulator/id1548356829
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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/opcodes/id6760205834
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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.
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Reposted by KIM-1
atrupar.com's profile picture
Aaron Rupar @atrupar.com
6d
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.
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New blog post - Roller Bearing IC Leg Straighteners:
blog.tynemouthsoftware.co.uk/2026/04/roller-bearing-ic-leg-straighteners.html
I have been after one of these for ages and accidentally bought a second one whilst looking for parts to improve the first.
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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
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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.
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Reposted by KIM-1
hansotten.bsky.social's profile picture
@hansotten.bsky.social
9d
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
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Reposted by KIM-1
hansotten.bsky.social's profile picture
@hansotten.bsky.social
9d
More on my website:
retro.hansotten.nl/6502-sbc/kim-1-manuals-and-software/kim-1-revisions-what-changed/
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In the #lounge waiting for the plane to #revision2026 #demoparty #6502 #commodore64
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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=qc3SVQQ54T0
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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/opcodes/id6760205834
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