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 growth 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 way in which I stumbled onto the Jupiter Ace, and being a FORTH-based laptop that was a business failure, I simply could not resist the diversion of constructing certainly one of these distinctive computer systems! That is usually how these journeys go — you begin down one path and encounter one thing fascinating alongside the way in which.”
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 beneath 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 had been bought earlier than the corporate folded a 12 months after launch, making people who stay collectors’ gadgets — and prime fodder for the cloning course of.
Electronics engineer Cees Meijer has gone by means of 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 undertaking’s Hackaday.io web page, “what’s missing in all these rebuilds is the precise housing, which to me is a large a part of the allure of this machine. And utilizing a 3D printer it can’t be too exhausting 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 parts, and making solely minimal adjustments, 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.
An glitch within the system was traced to unhealthy RAM timings, and solved with the addition of a delay within the write line. (📷: Dr. Scott M. Baker)
Baker wasn’t completely happy to cease the undertaking 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 couple of tips I got here up with for the sting connectors,” he explains. “The sting card connectors should be ‘open’ on the 2 ends. I made them by taking a larger-than-necessary connector and utilizing a hacksaw blade to rigorously minimize off the ends. For a ‘pass-through’ so you may 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, appropriate with Martyn Davies “Massive Mouth” board; and a Raspberry Pi Supervisor, powered by a Raspberry Pi Zero single-board laptop. “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 browse or write reminiscence. You’ll be able to PEEK and POKE your retro laptop from the comfort of your desktop laptop, to see what’s occurring contained in the retro laptop. You’ll be able to even push complete packages into reminiscence, or save the present state of reminiscence.”
Among the many add-ons is a Raspberry Pi Supervisor, which acts as a direct interface between a contemporary system and the Jupiter Ace. (📷: Dr. Scott M. Baker)
“On some computer systems,” Baker continues, “such because the Jupiter Ace, I have been in a position to push keystrokes straight into the keyboard buffer and obtain display screen captures. This lets me do software program improvement from my Home windows desktop throughout the room, but nonetheless do it ‘on’ the retro laptop. Reasonably 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 beneath an unspecified license.
