Dr. Scott M. Baker Builds Cees Meijer’s Jupiter Ace Clone — and Three New Add-On Modules

Dr. Scott M. Baker has taken a break from Heathkit tasks to place collectively a duplicate Jupiter Ace microcomputer, based mostly on a design by Cees Meijer — then designed three of his personal enlargement modules for good measure.

“It began once I acquired a speech synthesizer for the Timex Sinclair and set off to construct myself a Timex Sinclair clone,” Baker explains. “Alongside the best way I stumbled onto the Jupiter Ace, and being a FORTH-based pc that was a business failure, I simply could not resist the diversion of constructing one among these distinctive computer systems! That is usually how these journeys go — you begin down one path and encounter one thing attention-grabbing alongside the best way.”

Jupiter Cantab launched the Jupiter Ace in 1982, aiming to supply competitors to the Sinclair ZX81 (launched because the Timex Sinclair 1000 within the US) with some massive variations below its plastic hood — not least of which was its use of the FORTH language instead of the BASIC which was widespread to most eight-bit microcomputers of the period. Only some thousand have been offered earlier than the corporate folded a yr after launch, making people who stay collectors’ gadgets — and prime fodder for the cloning course of.

Electronics engineer Cees Meijer has gone by the method of designing a clone of the Jupiter Ace, proper right down to the plastic case — “as a result of,” Meijer explains in his mission’s Hackaday.io web page, “what’s missing in all these rebuilds is the precise housing, which to me is a big a part of the appeal of this machine. And utilizing a 3D printer it can’t be too laborious to copy this.”

As if to show his level, Baker has taken Meijer’s design and replicated it — having the KiCad PCB design information manufactured, sourcing the required elements, and making solely minimal modifications, although not with out some difficulties with the video output which required the elimination of a 555 timer from the circuit and the addition of a delay within the RAM write sign so as to add compatibility with 6166 static RAM (SRAM) elements.

Baker wasn’t pleased to cease the mission there, although, and set about constructing his personal add-on modules for the brand new Jupiter Ace clone. “Making new modules wasn’t troublesome, although there are a number of tips I got here up with for the sting connectors,” he explains. “The sting card connectors have to be ‘open’ on the 2 ends. I made them by taking a larger-than-necessary connector and utilizing a hacksaw blade to rigorously reduce off the ends. For a ‘pass-through’ so you’ll be able to piggyback one module behind one other, I used a small stub board.”

Baker’s new modules are: a RAM board, which provides an additional 48kB of reminiscence to the system; a speech synthesizer module, suitable with Martyn Davies “Huge Mouth” board; and a Raspberry Pi Supervisor, powered by a Raspberry Pi Zero single-board pc. “The Pi Supervisor is a board that I first constructed for the RC2014,” Baker explains.

“I acknowledged how helpful it might be to simply pause the CPU and skim or write reminiscence. You’ll be able to PEEK and POKE your retro pc from the comfort of your desktop pc, to see what’s happening contained in the retro pc. You’ll be able to even push complete packages into reminiscence, or save the present state of reminiscence.”

“On some computer systems,” Baker continues, “such because the Jupiter Ace, I have been capable of push keystrokes immediately into the keyboard buffer and obtain display captures. This lets me do software program growth from my Home windows desktop throughout the room, but nonetheless do it ‘on’ the retro pc. Moderately than laboriously sort a complete program on the Ace’s keyboard, I can simply paste the entire thing into the keyboard buffer.”

Baker’s full write-up is on the market on his web site; supply code, schematics, and board design information for the add-on modules can be found on GitHub below an unspecified license.