Dr. Scott M. Baker has taken a break from Heathkit initiatives to place collectively a reproduction Jupiter Ace microcomputer, based mostly on a design by Cees Meijer — then designed three of his personal growth modules for good measure.
“It began after 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 pc that was a industrial failure, I simply could not resist the diversion of constructing one in all these distinctive computer systems! That is typically how these journeys go — you begin down one path and encounter one thing attention-grabbing 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 frequent to most eight-bit microcomputers of the period. Only some thousand had been offered earlier than the corporate folded a yr after launch, making those who stay collectors’ objects — and prime fodder for the cloning course of.
Electronics engineer Cees Meijer has gone via the method of designing a clone of the Jupiter Ace, proper all the way 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 attraction of this machine. And utilizing a 3D printer it can’t be too onerous to duplicate 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.
An glitch within the system was traced to dangerous RAM timings, and solved with the addition of a delay within the write line. (📷: Dr. Scott M. Baker)
Baker wasn’t comfortable 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 just a few methods 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 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, suitable with Martyn Davies “Large 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 only pause the CPU and skim or write reminiscence. You possibly can PEEK and POKE your retro pc from the comfort of your desktop pc, to see what’s happening contained in the retro pc. You possibly can even push entire applications 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 instantly into the keyboard buffer and obtain display screen 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 an entire program on the Ace’s keyboard, I can simply paste the entire thing into the keyboard buffer.”
Baker’s full write-up is offered 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.