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6502 posts - new projects and interesting old projects from the archives
6502 posts - new projects and interesting old projects from the archives

mos6502's posts

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This week, building a portable computer - see the tiny LCD display there? Batteries included too, with a one hour battery life if you're lucky. Like many retro projects, this one has solid state storage based on SD Cards. The mainboard is from Acorn's BBC Master Compact, which is a more-integrated and cost-reduced version of the Master, with an external PSU and disk drive unit not needed for these portable purposes, and with all the goodness of the Master - with the exception of support for a coprocessor. So, no 274MHz 6502-in-a-Pi addon for this machine. (That's a reference to PiTubeDirect, if you haven't been following along!)
Be sure to click through for the great photos of Stephen Barriball, the designer, builder and owner, enjoying portable 6502 computing on the beach! "Had to fight my way onto the beach through the hordes of Spectrum and Commodore 64 users..."

From the thread Portable BBC Micro at

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This week, some IDEs where you can develop your 6502 code and see the results running within the comfort of your browser. The most recent, and still a work in progress, is +Matt Godbolt's BeebIDE, which offers a BeebASM flavour of assembly language, embedded in something like a BBC Basic. It's worth a visit just for the demo, but watch out for the loud beeps at startup, which is of course faithful to the Acorn experience.
Second up, in no particular order, is Steven Hugg's 8bitworkshop, where you'll be programming for the Atari VCS aka 2600, with a number of demo programs to help you learn the machine.
Finally, in our featured set of photogenic IDEs, is +Peter Noyes's Dodo Playground, featuring a tutorial and emulation of his homebrew 6502 gaming platform.
But finally finally, we'll have to mention Nick Morgan's easy6502 tutorial - not so photogenic, but a useful tutorial to get started if you don't already know 6502, and also useful for testing small fragments of code.
All of these, and more, are catalogued at
3 Photos - View album

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This week, a very neat embedded emulation of the KIM-1 from Mats Engstrom, using a surface mount AVR chip and not much else. You can see the back side of the board at the forum:
but unfortunately this project seems to be very quiet - so perhaps for a micro portable 6502 fix you should look up Oscar's KIM-Uno project...
... or perhaps chat to +Alun Jones about his ESP8266 wifi module with 6502-emulating firmware on board.

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This week, two really small programs for the 6502. First is the larger one, at 1k bytes, it's Óscar Toledo's port of his intelligent chess to the Atari 2600, aka the VCS. (If 1k seems a bit large, he's made a 596 byte version without the graphical interface, which you can run on the visual6502 - it will take about 15 mins for a move but what can you expect when you simulate 3500 transistors in JavaScript?) Check his GitHub repo and YouTube video too. Unfortunately he hadn't the space to use the Venetian blinds trick to display the pieces, so it is a bit of a flicker-fest.
"Of the 1024 bytes, the AI engine uses 429 bytes (initialization+engine+tables), the repetitive nature of the TIA display occupies the remaining bytes. Still remains 30 bytes free for improvements."
Our second tiny game is also for the 2600. You may know the machine offers only 128 bytes of RAM, and usually 2k or more in ROM for code. That RAM has to serve for all the scratch space and the stack. Well, Thomas Jentzsch has written a version of Pong which loads the whole game into the 128 bytes of RAM, so you can remove the cartridge and keep playing:
Originally the title screen and options menu made this a 2k cart, but Thomas shrunk it down to 1k for the Hackaday challenge.

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This week, a reboot of PLASMA, a virtual machine for c-like programming on 6502. Originally for Apple II by David Schmenk, ported to BBC Micro by Steve F. The Apple has a fairly large flat memory space - PLASMA can even self-host its own compiler and text editor as well as the VM. On the Beeb, Steve can run a small model in 32k, a larger model in a machine with a 64k copro, or a very large model in a machine with lots of sideways RAM.
The VM (bytecode interpreter) needs only about 6k.
See also David's presentation at KansasFest in 2015: He's presenting direct from the PLASMA editor and command line!

Steve's work is in his GitHub fork:
"Proto Language AsSeMbler for Apple"
where you'll also find some example programs - the Rogue game, a sieve benchmark, a Hanoi demo, and more.

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This week, a portable 6502 computer, in the form of a KIM-1 in a briefcase, with tape storage built in. This photo from VCF SW 3.0 in Arlington - more in the album of course, including a Commodore SX-64, a more conventional idea of the same thing - a luggable self-contained machine, mains powered. On the same lines, Acorn's 65816-powered Communicator has been seen in a briefcase format - it's even on view at TNMoC in the UK - and there's one at the CCH also in the UK:
And we should mention the Apple IIc, very much a recognisable portable form factor, although again powered by mains. Like the Acorn, you'll need a friend to carry the monitor for you, as there's no display on board.
There's a homebrew Acorn Atom portable - just one - but you can make one too:
These days LCD and OLED displays are affordable, and batteries are much better than they used to be.

Finally, let's mention the Commodore LCD "presented at the January 1985 Consumer Electronics Show, but never released"
and available as an in-browser emulation at

via a thread on classiccmp mailing list

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This week, the story of a TIM, by Joseph Watson - from 1975, about as early as you can get, and the earliest 6502-based kit computer design. MOS Technology made the 6502 CPU, of course, but also some very useful peripheral chips - the RRIOT even included ROM, and so there were a few variants which came with different programs. You can read more about the RRIOT nearby, at
and more about various early monitor programs in our previous post at

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How was your #retro2016? Here are some 6502 highlights from our year of weekly posting... perhaps the most visually memorable is the Limpfish 1000 breadboard system which runs EhBasic. Other builds this year: +Jac Goudsmit's L-Star which is now a kit on Tindie, and +Peter Noyes' Dodo gaming system which now has a web-based IDE.
We also saw the release of PiTubeDirect, a cheap Raspberry-Pi based peripheral which boosts the BBC Micro to an amazing 274MHz. The related Matchbox Copro got a speed boost too, and both got mapped memory so they can run huge programs - we even saw a Turing Machine implemented in Conway's Game of Life, running on a Pi-fitted Beeb.

We saw a couple of interesting peripherals fitted to 6502 too - the ESP8266 WiFi module and the CH375B USB Mass Storage Controller.

Most spectacular perhaps was +Eric Schlaepfer's one-off MOnSter 6502 built with thousands of discrete transistors. Perhaps inspired by it, Andrew Holmes fitted a transistor-level model of the 6502 into an FPGA.

Over on the forums, we saw these discussions among many others:
"Bil Herd: Tales From Inside Commodore" video
Visual 6502 and Undocumented Opcodes
Were there any early 6502 machines with a front panel?
Embedded emulation on PIC, AVR/Arduino, ARM etc
New game for easy 6502 simulator
OT: DIPSY - tiny FPGA allows for 6502 in 8 pin DIP?
Simple 3-Chip design Proof-of-Concept

Here's to an interesting and productive 2017 - whether you're building, deconstructing, debugging or collecting, make sure it's a 6502!

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This week, the 6502 in astronomy, to mark a happy Solstice to all our readers. At the Lick Observatory you'll find a 6502 controlling the 120-inch Shane reflector, with the help of a PET and a PDP-8 - at least, you would find this back in 1980. We rather hope it's still in service. Read all about it in the Infoworld article at
or for more technical info search for "lick observatory tv autoguider" - remarkably, the 16k PET is running several BASIC programs which among other tasks keep the system clock tuned to within a tenth of a microsecond!
Also related to pointing things at stars, we notice an AIM-65 being used at Sandia National Laboratory to point solar panels at the Sun - see
to read all about a system called TACS - the Tracking and Control System.
We'll be skipping next week's post, as usual for this time of year - have a good time without us - and will be back for an annual roundup.

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This week, a couple of 6502-related competitions. First up, the Hackaday 1k challenge. How much can be squeezed into 1k on a 6502? It's open over the end of the year so you have a few weeks to get your act together.
We notice that the VTL02 interpreter is under 1k, we're told a Life can even fit inside 512 bytes, Bruce Clarks's pi program is under 300 bytes, and his single-page monitor is just a single page. But Lisp and Forth and even TinyBasic are much bigger, as far as we can tell. And Peter Jennings' famous chess was just a little over 1k, which is annoying considering the Z80 has an under-1k chess program...

The second competition we've noticed is the almost-annual Shoot-Em-Up-Construction-Kit competition, now extended to the end of Jan. It would be too punnish to call this software a game-changer, but surely it lowered the barrier to making a slick game on the C64 - and on other platforms too.

If you like SEUCK, perhaps you'll like SEUCK Redux by Martin Piper, "a new game engine that runs SEUCK data files. The aim was to reduce the amount of flickering and glitching caused by having too many sprites onscreen, and to free up screen time to run music alongside the game" as seen at
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