BreadBin Is An 8-bit TTL CPU On A Breadboard, In A Bread Bin

October 5, 2021 by Robin Kearey 11 Comments

Building a CPU out of logic gates is a great way to learn about the inner workings of microprocessors, and we’ve seen several impressive projects in this area. [c0pperdragon] set himself the task of designing a very capable 8-bit CPU using just 74HC type logic chips on a large plug-in breadboard. To emphasize the “bread” theme, he put the whole thing inside an actual bread bin and named the accompanying software BERND after an anthropomorphic loaf from a German TV channel.

Getting a reliable breadboard big enough for the task at hand required some engineering by itself: cheap breadboards often have trouble making a reliable contact at each and every pin, while the length of the ground path and lack of shielding cause trouble for high-speed circuits. [c0pperdragon] therefore bought high-quality breadboards and soldered the ground wires together to get a proper low-resistance path. A ground plane made of aluminium foil should also help to prevent signal integrity issues.

The total circuit is incredibly compact for a complete CPU, using just 33 chips. This includes 64 KB of flash to store programs as well as a 555 timer to generate a clock signal. I/Os are limited to simple eight-bit input and output buses, but a sixteen-bit address bus gives it plenty of space to add ROM, RAM or fancier interfaces.

The aforementioned BERND program is an emulator that allows the BreadBin to run code written for the 65C816 processor, the 16-bit CPU used in the Super Nintendo and the Apple IIGS. This makes it easy to re-use programs developed for [c0pperdragon]’s earlier OS816 system, which uses an actual 65C816 chip.

This has to be one of the cleanest breadboard CPU designs we’ve seen so far, certainly a lot cleaner than this one. If you’d like to watch a detailed guide to building an 8-bit CPU on a breadboard, we recommend this project.

The MiniITX Retro System

March 16, 2019 by Brian Benchoff 12 Comments

There are hundreds of modern, retrocomputing projects out there that put ancient CPUs and chips in a modern context. The Neon816 from [Lenore] is perhaps one of the most impressive projects like this we’ve seen. It’s a classic system in a modern form factor, with modern video output, mashed together into a MiniITX motherboard.

The powerhouse of this computer is the Western Design Center W65C816 CPU. This is the second generation of the venerable 6502 CPU, the same chip found in everything from the Commodore 64 to the Apple II to the Nintendo Entertainment System. The 65816 is a 6502 at start-up until you flip a bit in a register, at which time the signalling on the address bus becomes much weirder. We’ve seen some single board computers based on the 65816 before and The 8-Bit Guy has a few ideas to build a computer around this CPU, but for the foreseeable future work on that will be trapped in development hell.

Of note, the Neon816 will feature DVI output (I guess technically you can just run the analog signals through the connector), a PS/2 Joystick input, two Atari / Sega joystick ports, MIDI in and out, a PC-style floppy disc connector, and a Commodore serial bus. It’s a hodge-podge of classic retrotainment, all in a single MiniITX motherboard.

The key other feature of the Neon816 is an FPGA, specifically a Lattice XP2 8000 LUT chip that is used for video and audio. This is combined with 1MB of main RAM (looks like a simple SRAM) and 128k of Flash storage for the ROM. There’s also an SD card in there for storage.

Right now, [Lenore] is populating the first prototype board, and we can’t wait to see some video generated with this impressive little system.

Winning The Console Wars – An In-Depth Architectural Study

November 6, 2015 by Brian Benchoff 78 Comments

From time to time, we at Hackaday like to publish a few engineering war stories – the tales of bravery and intrigue in getting a product to market, getting a product cancelled, and why one technology won out over another. Today’s war story is from the most brutal and savage conflicts of our time, the console wars.

The thing most people don’t realize about the console wars is that it was never really about the consoles at all. While the war was divided along the Genesis / Mega Drive and the Super Nintendo fronts, the battles were between games. Mortal Kombat was a bloody battle, but in the end, Sega won that one. The 3D graphics campaign was hard, and the Starfox offensive would be compared to the Desert Fox’s success at the Kasserine Pass. In either case, only Sega’s 32X and the British 7th Armoured Division entering Tunis would bring hostilities to an end.

In any event, these pitched battles are consigned to be interpreted and reinterpreted by historians evermore. I can only offer my war story of the console wars, and that means a deconstruction of the hardware.

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Review: Single Board 65C02 And 65C816 Computers

July 29, 2015 by Brian Benchoff 51 Comments

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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