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One of the designers whose work we see constantly in the world of retrocomputing is [Grant Searle], whose work on minimal chip count microcomputers has spawned a host of implementations across several processor families.
Often a retrocomputer is by necessity quite large, as an inevitable consequence of having integrated circuits in the period-correct dual-in-line packages with 0.1″ spaced pins. Back in the day there were few micros whose PCBs were smaller than a Eurocard (100 mm x 160 mm, 4″ x 6.3″), and many boasted PCBs much larger.
[Mark Feldman] though has taken a [Grant Searle] 6502 design and fitted it into a much smaller footprint through ingenious use of two stacked Perf+ prototyping boards. This is a stripboard product that features horizontal traces on one side and vertical on the other, which lends itself to compactness.
On top of [Mark]’s computer are the processor and EPROM, while on the lower board are the RAM, UART, clock, and address decoding logic. It runs at 1.8 MHz, has 16 kB of ROM and 32 kB of RAM, which seems inconsequential in 2017 but would have been a rather impressive spec in the early 1980s.
There are three rows of pins connecting the boards, with the address bus carried up the middle and everything else at the edges. He’s toying with the idea of a third layer containing a keyboard and video display driver, something to look forward to.
The computer isn’t all on the page though, rather than wait for one to arrive he’s built his own EPROM programmer on a breadboard. He doesn’t have an eraser though, so has resorted to the Australian sunshine to (slowly) provide the UV light he needs.
We’ve featured other [Grant Searle] designs before, including a Sony Watchman clock with a Z80 board behind it, and another tiny board, this time with a Z80 rather than a 6502.
Filed under: classic hacks
