Reinhard Grafl’s Single-Breadboard Pc Packs Eighties Know-how Right into a Tiny 5-Chip Footprint


Classic computing fanatic and {hardware} engineer Reinhard “c0pperdragon” Grafl has put collectively a MOS 6502-based laptop with a distinction: the whole factor suits on to a compact breadboard and makes use of solely 4 built-in circuits plus a crystal oscillator.

“Designs for SBCs [Single-Board Computers] primarily based on the [MOS Technology] 6502 are fairly frequent, however usually they use some specialised ICs [Integrated Circuits] to deal with the IO [Input/Output]. I did some designs myself utilizing commonplace 74-logic for the auxiliary performance,” Grafl explains. “Pushing the minimalist method to the intense, I made a decision to discover a approach to match a 65C02-based laptop into 5 ICs together with oscillator, CPU, RAM and ROM.”

Earlier than setting about constructing the surprisingly compact machine, Grafl set himself 4 key specs: it had to have the ability to run a WDC 65C02, a contemporary incarnation of the traditional MOS 6502, at 10MHz; it needed to embody 32kB of RAM; it needed to provide 32kB of ROM storage; and it wanted to make use of software-driven IO, to cut back the element depend. Oh, and it wanted to suit right into a single BB630 breadboard.

“The BB630 board is large enough to suit the obligatory CPU/RAM/flash ICs and one further small IC,” Grafl explains. “This extra IC has to in some way implement all he mandatory logic for each the reminiscence addressing in addition to for the IO. A quad two-input NAND (74HC00) is a fairly versatile possibility right here. Some very slender areas between these ICs can be utilized for a little bit of analog circuitry.”

For these trying to construct their very own Grafl has uploaded KiCad venture information for the SBC, together with a schematic and a proposed PCB design, to GitHub underneath an unspecified open supply license, together with a short demonstration utility. “I do not indent to do rather more programming on this machine,” Grafl admits.


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