With the Good Chip Scarcity continue to delaying deliveries of new components, now may well be a great time to look close to your lab and examine all those piles of chips that you assumed “might occur in helpful one day”. Likelihood are you’ll find a fantastic stack of 74xx series logic, after ubiquitous but nowadays primarily out of date many thanks to strong microcontrollers and FPGAs. It would be a shame to permit them go to squander, so why not use them to make a neat 1980s-design personal computer?
With this thought in thoughts, [Anders Nielsen] built the ABN6502: a single-board computer based mostly on the venerable 6502 processor, but with somewhat contemporary interfaces like a VGA monitor output, a PS/2 keyboard connector and even a wireless module to simplify firmware uploads from a Laptop. One structure necessity was to limit the variety of new components desired the normal hacker fascinated in creating the ABN6502 will in all probability have lots of of the chips lying all-around someplace in their workshop.
The element list reads like a usual invoice of resources for a 6502-based mostly laptop, but comes with a whole lot of overall flexibility to let for element subsititution. For the CPU, equally the common NMOS 6502 as very well as the modern CMOS-based 65C02 are supported, along with their 6522 companion chip that supplies I/O ports and timers. A ROM socket can keep both fashionable, quickly flash chips or traditional but slow UV-erasable EPROMs.
Instead of employing DRAM chips with their complicated refresh specifications, [Anders] went for 32 KB of SRAM to put into action the key memory unaffordable in the ’80s but very easily available right now. Typical 74xx collection logic chips glue all the components alongside one another, all over again with quite a few possibilities to increase or remove characteristics as the person prefers. Pin headers deliver out the I/O ports for effortless relationship to external peripherals.
The ABN6502’s computer software library is presently constrained to a bootloader, but a total growth toolchain centered on the CC65 compiler need to make it straightforward to produce all sorts of packages on this system. We’ve now highlighted the intelligent wireless ROM flashing program, as well as a demonstration of the 6502 driving RGB LEDs.