With the Good Chip Scarcity nevertheless delaying deliveries of new components, now could possibly be a fantastic time to appear about your lab and inspect people piles of chips that you assumed “might appear in helpful one day”. Likelihood are you’ll uncover a good stack of 74xx series logic, at the time ubiquitous but today largely out of date thanks to strong microcontrollers and FPGAs. It would be a shame to let them go to squander, so why not use them to make a neat 1980s-design and style computer?
With this strategy in thoughts, [Anders Nielsen] built the ABN6502: a single-board personal computer based mostly on the venerable 6502 processor, but with comparatively present day interfaces like a VGA check output, a PS/2 keyboard connector and even a wireless module to simplify firmware uploads from a Computer system. Just one design requirement was to limit the range of new elements desired the common hacker interested in setting up the ABN6502 will probably have numerous of the chips lying around someplace in their workshop.
The part checklist reads like a typical invoice of supplies for a 6502-based mostly personal computer, but comes with a lot of flexibility to permit for part subsititution. For the CPU, equally the vintage NMOS 6502 as properly 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 hold possibly fashionable, rapid flash chips or conventional but gradual UV-erasable EPROMs.
As an alternative of applying DRAM chips with their sophisticated refresh demands, [Anders] went for 32 KB of SRAM to put into practice the major memory unaffordable in the ’80s but easily offered nowadays. Typical 74xx collection logic chips glue all the components alongside one another, once again with a number of possibilities to include or take away functions as the consumer prefers. Pin headers deliver out the I/O ports for uncomplicated link to exterior peripherals.
The ABN6502’s software package library is presently restricted to a bootloader, but a comprehensive enhancement toolchain dependent on the CC65 compiler really should make it easy to create all types of courses on this system. We’ve by now featured the clever wireless ROM flashing system, as nicely as a demonstration of the 6502 driving RGB LEDs.