Review: Single Board 65C02 and 65C816 Computers

The 6502 is a classic piece of computing history. Versions of this CPU were found in everything from the Apple ][, to the Nintendo Entertainment System, and the Commodore 64. The history of the 6502 doesn’t end with video games; for the last forty years, this CPU has found its way into industrial equipment, medical devices, and everything else that doesn’t need to be redesigned every two years. Combine the longevity of the 6502 with the fact an entire generation of developers first cut their teeth on 6502 assembly, and you have the makings of a classic microprocessor that will, I’m sure, still be relevant in another forty years.

The cathedral of The 6502 is Western Design Center. For more than 35 years, WDC has been the home of 6502-related designs. Recently, WDC has been interested in the educational aspects of the 6502, with one of the VPs, [David Cramer], lending his time to an after-school club teaching opcodes.

The folks at WDC recently contacted me to see if I would give their hardware a close look, and after providing a few boards, this hardware proved to be both excellent. They’re great for educators adventurous enough to deviate from the Arduino, Processing, and Fritzing zeitgeist, and for anyone who wants to dip their toes into the world of 65xx development.

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Hacklet 38 – 6502 Projects

The 6502 CPU is probably the most famous of all the 8-bit processors out there, whether in the form of bare chips for homebrew computers, or as slightly modified derivative chips found in everything from the C64, the NES, and the BBC Micro. For this edition of the Hacklet, we’re taking a look at all the 6502-based builds on hackaday.io.


6917521396192751941There aren’t many transistors on a 6502, making it perfect for implementing on an FPGA. [Michael A. Morris] has an Arduino FPGA shield, and his soft-6502 project is called Cameleon. There’s a bunch of SPI Flash and FRAM on board, and the 128kB of (parallel) SRAM on the board is more than enough to handle any computational task you can throw at it.

Since the Cameleon is built on programmable logic, [Michael] thought it would be a good idea to put some of those unused opcodes to use. There are instructions for coprocessor support, and a bunch of instructions specifically designed to make the Forth implementation easier.


4244551421640813832Maybe programmable logic isn’t your thing, and you’d just like a simple computer like the Ohio Scientific or the Apple I. The L-Star is for you. That’s [Jac Goudsmit]’s build featuring a 6502, a Parallax Propeller, and little else.

The Parallax Propeller is a powerful (multi-core!) chip that’s easily capable of handling video out, keyboard in, and serving up the ROM and RAM of a computer. [Jac]’s build does it all beautifully, and if you’re looking for the easiest way to run code on a 6502, this is how you do it.


6502s were found in just about everything, and while poking around at the local e-waste recycler, he stumbled upon something rather interesting. The case badges screamed, “BS medical device”, but after poking around a bit, he figured out this was an MTU-130 system, a machine that was apparently the top of the line in its day.

There’s some weird stuff going on in this machine – 18-bit addressing and 80kB of RAM. So far [Eric] has managed to dump the ROM, and he’s taking a look at the floppy controller board to see if he can figure out how it’s mapped. It’s one thing to figure out what’s broken on an Apple II or C64; those are well documented machines. It’s another thing entirely to figure out a machine very few people have heard of, and we tip our hat to [Eric] and his efforts.


4000511410347834190Here’s a build that both does and doesn’t have a 6502 in it. [BladeRunner]’s SheMachine is a single board computer that has a 65c816 in it. The ‘816 is an interesting beast that operates as a standard 6502 until a bit is flipped in one of its registers. After that, it has a 24-bit address space for addressing 16 Megabytes of memory, 16-bit registers, but is still completely backwards compatible with the 6502. Yes, it does have weird interleaved address pins, but we can only imagine what the world would be like if this chip came out a few years earlier…

[BladeRunner] is designing the SheMachine with 1MB of SRAM – more than enough, really – and is mapping all the memory through a CPLD. That’s how you should do it, anyway.

Homebrew computer is 16 bits of awesome

We’ve seen our share of homebrew computers over the years. Usually, these bare-bone systems use a small, early 80s-era microprocessor such as the Z80 or 6502. These little 8-bit machines are awesome, but somewhat limited in their capability. [BigDumbDinosaur] sent in a computer he’s been working on for a few years now featuring the infamous 65816 CPU – the same CPU found in the Apple IIgs, the Super Nintendo, and [Jeri Ellsworth]’s C-ONE computer.

The 65816 is a direct descendant of the venerable 6502 CPU found in the Commodore 64, Apple II, and just about every 80s microcomputer of note. [BigDumbDinosaur] chose the 65816 for its backwards-compatibility with the fun to program 6502 and the ability to use high clock rates and tons of address space for a very cool design.

After a ton of careful design and consideration, [BigDumbDinosaur]’s computer included a real-time clock, a watchdog timer, a serial port, 256kB of ROM, and 128kB of RAM.

It’s a really wonderful build, but [BigDumbDinosaur] isn’t done with this project yet. He’s working on version 2 of a 65816 computer that will use programmable ‘glue’ logic, a lot more RAM, have a SCSI interface (for a hard drive), and have preemptive multitasking.

An awesome job, and it’s wonderful to see the wonderful 65816 make its way into another homebrew computer. Now if only we could find a 68000-based homebrew computer…