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This week, the front panel of a Burroughs 220, as seen emulated on an Apple II. Micheal J Mahon is rightly famous for his two Apple Crate parallel computers utilising his NadaNet technology and made from Apple II motherboards, but here we see a major software project, an emulation of the valve-based B220 which has great nostalgia value for him:
"The Burroughs 220 was the last commercial vacuum tube computer... one of the first computers that I programmed. In 1963 it had already been superseded as Caltech's primary computer system, by an IBM 7090. When the campus computing load moved from the B220, it became a "research computer" for which students and faculty could sign up (on a blackboard) for blocks of time. Since this seemed the ideal environment for learning a machine and experimenting, I was immediately drawn to it. Though I didn’t realize it, it was essentially a room-sized personal computer!
When I “met” the Caltech B220, it didn’t have a symbolic assembler. It did have an Algol 58 variant compiler, known as BALGOL..."

The machine was word-addressed, with 11 decimal digits in each word, and in this case 5000 words total. Just about room for that in 30 thousand bytes of RAM, leaving room for the emulator and the user interface. (Yes, it's all thousands - no 1024 multipliers here.)

The emulator manages to run at about half real speed on a 1MHz Apple II - that is, at about 100kHz effective clock speed, and of course faster Apples are available.

Several PDFs and a program listing or two here:

Hat tip to +David Galloway for the post idea!
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This week, DOS65 - not just an OS but a whole ecosystem, especially for your Octopus 65 as seen in Elektuur magazine. DOS65 comes with Basic, Comal, Pascal, Forth and even a tiny C compiler, as well as a macro assembler, some comms applications, and a logic analyser. All explained and preserved on Hans Otten's site. Nice to see that this was a team effort from an active community.
(Not to be confused with DOS/65 which we covered previously:
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This week, a look at CP/M on 6502 machines... yes, really. But always with a Z80 nearby. Featured here is the Basis 108 from the early 80s, a solid Apple II workalike from Germany. "To achieve compatibility with CP/M, Basis had an extended graphic card supporting 80-column mode. CP/M Mode was selected by switch in front of the computer. Basis 108 had cassette interface, serial and parallel port onboard. Keyboard was external, connected with 7-bit parallel ASCII port." (+Hans Franke tells us the 108 was not merely a clone, but the first.)
Because CP/M was a widely used portable standard OS in business at that time, it was quite a popular idea to make it available as standard or as an add-on to a 6502 machine. We posted about this before[1], and in the comments +Zoran Davidovac told us "you did miss c128DCR( cost reduced ) actually it had on same board 8502-2MHz, 65c02-2MHz(floppy) and Z80-4MHz total 3 CPUs with dual chips for Video out :)"
(Have a look at for this one)

From 1987 we note a CP/M addon for Acorn's atom:

Also in the land of Acorn, from about 1984, the high-spec ABC series of Business Communicator machines included the 110, a dual-CPU CP/M capable model. See
(Inside, it's a B+ with a Z80 co-pro)

For a modern project to add to your Acorn machine, the matchbox FPGA offers a 112MHz equivalent Z80 and the Raspberry PiTubeDirect offers 120MHz:

(Hat tip to +Andrew Stadler for bringing the Basis 108 to our attention)

[1] Our previous post:

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This week, artificial life for your 6502 - Apple II originally, then other machines. Not just Conway's Life, but also Wireworld, and several other cell-based automata - and not only is the whole thing table-driven, allowing for a great variety of rulesets, but it's embedded in a Logo allowing for programmatic exploration. This is a terribly rare piece of software, which came with a book - or perhaps it was a book which came with software. If you have a copy, let us know! We can't find it anywhere.
Wireworld is especially interesting as it was invented to allow the easy construction of logic and computers within the world. It was invented in 1984, published with the Phantom Fish Tank in 1987, and became very well known after an article in Computer Recreations in Scientific American in 1990.

You can read all about it here:

And you can see a computer constructed in Wireworld and computing prime numbers here:
Run that computer in your browser here:

Remarkably, this same Brian Silverman was one of the team making the Visual 6502 simulator, many years later.
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This week, a raycasting fantasy role playing game in development for the Apple II and the C64. The game is open source, and there are development logs and some short videos too as well as demos. Here's their site:
and here's the repo:
where we see the state of play described as:
We have some cool routines written, but are still in our infancy:
- Fast tile drawing using text page 1 ($400-$7ff) as scratchpad
- Crazy awesome Hi-res 3D raycaster engine
- Module-based memory management which can utilize extra ram whenever possible
- PLASMA interpreter
We need a lot more, and ideas are greatly appreciated for the following:
- 2D tile drawing engine
- Mockingboard playback routines
- Ensoniq DOC playback routines
- Image depack routines, with support for animation frames and transparent overlays.
(but it wouldn't be too surprising if that documentation was a little out of date)

Via +Quinn Dunki at

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This week, shellcode on the 6502 - machine code programs which use only printable characters. +Chris Baird outlines the problem here, and shows us his solution at
It turns out there are very few opcodes available, and synthesising more means writing to memory - but only using printable-range addresses. Quite the technical challenge. "Note that memory can only be modified with ROL, ROR, and LSR!"
Mike B on the 6502 forum points out a different approach used on the Apple II, where there's a handy machine code monitor ready to interpret printable commands. So Ivan Drucker's Slammer! software can read such commands from your REM statements, to bridge the gap between Basic and machine code. There's an explanation and video at
but it seems Slammer itself isn't printable only, so Chris does seem to have done something new in 6502 land - well done Chris!
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This week, a 6502 retro-challenge project, to re-make Computer Space - the first arcade video game, from 1971. Yes, 1971 - with a wonderful futuristic cabinet but using dedicated TTL logic chips and not a microprocessor in sight. It was created by Nolan Bushnell and Ted Dabney, who subsequently founded Atari, a staple of our 6502 posts. But here we see +Norbert Landsteiner's project to remake the game on a Commodore PET - source code included, and an in-browser emulator in green or white - but also with a series of technical articles about how it was done. It's no mean feat, getting the 1MHz 6502 to update the screen within the vertical blanking interval - which is necessary to avoid unslightly snow, because the PET's memory is slow and the video generation simple.
Here's Norbert's index to his articles: We'd say this project is a resounding success, even if technically it over-ran the one-month window. Better to have a finished project that's a bit late!
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This week, generative music and video: a C64 demo in one page, by Linus Akesson. Video within, together with a detailed technical description. "In the absence of an actual 256-byte compo, it was submitted to the Oldskool 4K Intro compo at Revision 2017, where it ended up on 1st place."
"The melody is generated by a linear-feedback shift register (LFSR). Thus, in one sense, the melody is randomly generated. But I spent a considerable amount of time tweaking the random process until I found something that was musically satisfactory."

via the discussion at
where we hear
"I love that the line number in the embedded basic program is also code."
and find more links to generated music.
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This week, let's talk about C64 disks and copy protection. We found a whole site about it, so pop over there and have a feast - we'll wait for you:
Back with us? Our featured link this week is one of a pair of guest posts on Michael Steil's site. The 15 Second Copy story, by Mike Pall, is about copying over a parallel cable - the 1541 disk drive being a 6502 computer system in its own right and having a VIA inside with a spare port. More about this here:
The other story on pagetable is the story of FCopy, by Thomas Tempelmann, which uses only the original serial cable, and copies in a few minutes - 5 times faster than the default, not as fast as the parallel version, but needing no hardware mods. Getting the necessary information and understanding in those days, especially if you're one of the first to think of something, is totally different from the picture today.
Be sure to read the comments on the articles - good extra information in there. Such as Thomas speaking of the 1541's software being written as a pair of tasks, as a remnant of the prototypes which had a pair of CPUs even in the floppy drive: the tasks for the second processor were moved in to the interrupt routine.
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This week, a bit of 6502 homebrew - we notice that Atari fans are still pushing the envelope with games for your 2600. There's an impressive Donkey Kong at
which was five years in the making, and there's more at the homebrew store:
But featured here is the crossover Princess Rescue - Wired did a writeup at
For more instant gratification, you can read about Flapple Bird (for the Apple, of cores) and play online - follow the links at There's a raft of software for the Oric at
but perhaps most intriguing is the Elite like game 1337 - have a look around the Web for more on that.
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