With the Terrific Chip Lack continue to delaying deliveries of new parts, now may well be a superior time to glimpse all-around your lab and inspect those piles of chips that you imagined “might occur in useful one day”. Chances are you’ll uncover a very good stack of 74xx series logic, at the time ubiquitous but now mainly out of date thanks to potent microcontrollers and FPGAs. It would be a disgrace to allow them go to waste, so why not use them to make a neat 1980s-type computer?
With this plan in intellect, [Anders Nielsen] developed the ABN6502: a single-board laptop or computer primarily based on the venerable 6502 processor, but with fairly modern-day interfaces like a VGA check output, a PS/2 keyboard connector and even a wi-fi module to simplify firmware uploads from a Laptop. Just one structure requirement was to lower the amount of new components essential the ordinary hacker fascinated in making the ABN6502 will likely have a lot of of the chips lying all around someplace in their workshop.
The part list reads like a typical invoice of materials for a 6502-centered laptop or computer, but comes with a whole lot of overall flexibility to enable for component subsititution. For the CPU, both equally the typical NMOS 6502 as very well as the fashionable CMOS-primarily based 65C02 are supported, alongside with their 6522 companion chip that delivers I/O ports and timers. A ROM socket can hold possibly modern-day, quick flash chips or regular but slow UV-erasable EPROMs.
In its place of working with DRAM chips with their complicated refresh prerequisites, [Anders] went for 32 KB of SRAM to carry out the key memory unaffordable in the ’80s but quickly accessible currently. Typical 74xx series logic chips glue all the parts with each other, all over again with various solutions to include or eliminate capabilities as the person prefers. Pin headers carry out the I/O ports for quick connection to external peripherals.
The ABN6502’s program library is at the moment constrained to a bootloader, but a complete development toolchain based on the CC65 compiler should make it easy to acquire all sorts of applications on this platform. We have by now showcased the intelligent wi-fi ROM flashing system, as well as a demonstration of the 6502 driving RGB LEDs.