Those would be interesting chips to examine, if I ever get through my current projects :-)

I had one of the early Jupiter Aces - the circuit board said something like v1.00 - and it had some added soldered wires on the board, correcting some errors, but it worked well enough. Forth was definitely what attracted me to it - I was frustrated with Basic on my Sinclair XZ81, and Forth seemed like a big step forward. And I think it was.

I was 14 or 15 at the time. The first summer I wrote a whole load of games, mostly in Forth, but sometimes Forth just wasn't fast enough. I got a copy of "Mastering Machine Code on Your ZX81", and learned Z80 machine code. If there was an assembler available, I didn't have it, so this was all hand-assembled. Getting jumps right was a total pain, as was debugging. Generally, it either worked first time, or you started from scratch again. Usually I got there in the end.

I sold those games through a ad in "Your Computer" magazine, and earned back the price of the computer several times. But recording and shipping tapes one at a time got tedious really fast, so I didn't take that any further.

My Ace got modified quite a bit over the next couple of years. An extra 16KB RAM pack was an early addition, taking it to a whopping 19KB. Because Forth was so compact, I never filled that up.

My mother worked for Chubb cash dispensers (ATMs for Americans) at the time, and at some point they scrapped a lot of equipment. She tipped me off, and we went round there one evening and liberated lots of cash dispenser pieces from a skip. Amongst these were several numeric keypads with lovely mechanical keys. I dismantled several keypads to take out all the individual keys and made a proper keyboard to replace the original dead rubber monstrosity.

At school, I was taking O-level Technology, and you had to do a final year project. I'd seen articles in "Your Computer" about competitions where a micro-mouse robot would have to find its way through a maze. That seemed like a cool idea to me, so I decided to make one, despite not really having much idea how. I hadn't done any digital electronics at that time, but my friend Johnny Tombs (who later went on to be a Professor of Electronic Engineering) had decided to make a parallel I/O port for his ZX Spectrum using TTL logic for his Technology project. I'm not sure where Johnny learned about digital electronics, but he knew what he was doing, and designed a nice elegant circuit board and etched it at home. The Ace had the same Z80A CPU as the Spectrum, so I figured his design could be adapted. After a lot of pleading, he gave my his design and spent some time explaining to me how it worked and loaned me his copy of Watford Electronics catalog. A couple of weeks later all the components arrived, and I spent a busy few days soldering up my modified I/O port on veroboard. Compared to Johnny's professional looking version, mine looked like a mess of wires and chips, but it worked!

So then when it wasn't playing games, my Ace rode about on the top of a fairly flaky micromouse, made in the school metalwork shop out of aluminium sheet, some lego motors, and some light sensors to detect maze walls, exploring mazes. It didn't win any prizes but it did get me an A in O-level Technology.

My school was throwing out an old teletype, so I scavenged that. Then I modified the parallel I/O port to output +/- 12V on one pin, and wrote software to bit-bang RS232 at 110 baud. Back before the Internet, just finding the specs for RS232 was not so simple - our local library was a bit limited in that way - but I got there in the end. A lot of guesswork and trial and error. I don't think anyone made a printer for the Ace, so I may have had the only one. Being able to print code listings really helped, even though the teleprinter only printed capital letters.

Somewhere over the years, with my parents moving house multiple times, the Ace disappeared. Many years later, I found one on Ebay, and still have it. But somehow I never fell back in love with it - it just wasn't as good as I remembered my rather non-stock one being at that formative time in my life.

> Also that simplicity is king. Complexity is the enemy.

As someone that has managed engineering teams for large projects, I 100% agree. One of the issues with computers IMO is that it has made bad engineering easier. Back when you had to check everything with a slide-rule, you had a real appreciation for the skill and engineering prowess and experience to make things absolutely dead simple.

One challenge was that while I started working on the Xbox 360 about three years before it would ship, we knew that the custom CPU would not be available until early 2005 (first chips arrived in early February). And there was only supposed to be one hardware spin before final release.

So I had no real hardware to test any of the software I was writing, and no other chips (like the Apple G5 we used as alpha kits) had the custom security hardware or boot sequence like the custom chip would have. But I still needed to provide the first stage boot loader which is stored in ROM inside the CPU weeks before first manufacture.

I ended up writing a simulator of the CPU (instruction level), to make progress on writing the boot code. Obviously my boot code and hypervisor would run perfectly on my simulator since I wrote both!

But IBM had also had a hardware accelerated cycle-accurate simulator that I got to use. I was required to boot the entire Xbox 360 kernel in their simulator before I could release the boot ROM. What takes a few seconds on hardware to boot took over 3 hours in simulation. The POST codes would be displayed every so often to let me know that progress was still being made.

The first CPU arrived on a Friday, by Saturday the electrical engineers flew to Austin to help get the chip on the motherboard and make sure FSB and other busses were all working. I arrived on Monday evening with a laptop containing the source code to the kernel, on Tuesday I compiled and flashed various versions, working through the typical bring-up issues. By Wednesday afternoon the kernel was running Quake, including sound output and controller input.

Three years of preparation to make my contribution to hardware bring-up as short as possible, since I would bottleneck everyone else in the development team until the CPU booted the kernel.

I called the simulator Sbox and it was just a simple console app. I didn't implement the GPU, so no graphics just the hypervisor and kernel and some simple non-graphics apps. I made it so that you could build the Xbox 360 kernel on your windows machine, then just run sbox.exe and it would automatically find the just built kernel image targeting the PPC64 and boot it. Then if you typed control-C it would drop into the kernel debugger as a sub process, and you could poke around at the machine state as if it were the real Xbox hardware, showing all the PPC instructions and registers. It was a lot of fun writing it, and quite useful.

Hey, we're building this tool to enable AI CAD model generation and Git-like source control.

Happy to answer any questions! Waitlist on our website.