The Great Chip shortage still delays the delivery of new ingredients, so now might be a good time to look around your lab and inspect the piles of chips that you thought might one day come in handy. Chances are you’ll get a good stack of 74xx series logic, which was once ubiquitous but mostly obsolete today thanks to the powerful microcontroller and FPGA. It would be a shame to let them go, so why not use them to create a neat computer in the style of 1980s?
With this idea in mind, [Anders Nielsen] The ABN6502 is designed: a single-board computer based on the Honorable 6502 processor, but with a relatively modern interface like a VGA monitor output, a PS / 2 keyboard connector and even a wireless module to facilitate uploading firmware from a PC. The requirement of a design was to reduce the number of new elements required; The average hacker interested in creating ABN6502 will probably have a lot of chips lying somewhere in their workshop.
The component list reads like a typical equipment bill for a 6502-based computer, but comes with a lot of flexibility for part replacement. For the CPU, both the classic NMOS 6502 and the modern CMOS-based 65C02 are supported, along with their 6522 companion chip that provides I / O port and timer. A ROM socket can hold a modern, fast flash chip or traditional but slow UV-removable EPROM.
Instead of using DRAM chips with their complex refresh requirements, [Anders] The main memory went for 32 KB SRAM for implementation; Impossible in the 80’s but easily available today. The standard 74xx series logic chips glue all the components together, again with several options for adding or removing features to the user’s liking. Pin headers pull out I / O ports for easy connection to external peripherals.
ABN6502’s software library is currently limited to a bootloader, but a complete development toolchain based on the CC65 compiler will make it easier to develop all kinds of programs on this platform. We’ve already shown off a display of clever wireless ROM flashing systems, as well as 6502 driving RGB LEDs.