[HN Gopher] The Curious Case of Jupiter Ace
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The Curious Case of Jupiter Ace
Author : ibobev
Score : 39 points
Date : 2025-04-10 12:39 UTC (10 hours ago)
(HTM) web link (nemanjatrifunovic.substack.com)
(TXT) w3m dump (nemanjatrifunovic.substack.com)
| rickcarlino wrote:
| The Jupiter Ace was before my time, but I found the user manual
| to be a very well written Forth tutorial:
| https://archive.org/details/Jupiter_Ace_Users_Manual_1982_Ju...
| rwmj wrote:
| Steve Vickers was my university lecturer circa 1995. His course
| was legendarily difficult, in contrast to his lucid tutorials
| in both the Jupiter Ace and ZX81 manuals! The list of his
| papers on Wikipedia should give you a flavour of what the
| course was about:
| https://en.wikipedia.org/wiki/Steve_Vickers_(computer_scient...
| aa-jv wrote:
| Minor correction in the article: The Oric-1 did ship with 16K RAM
| initially, but was widely available not long after in the 48K
| (really, 64K) configuration, and users could easily upgrade their
| 16K Oric-1's to the beefier RAM, and also conversions to Atmos-
| level Orics' were available widely as well.
|
| The Oric-1, however, did far better than the Jupiter Ace on the
| market - which isn't to say it was successful, just that it
| didn't quite flop as hard as the Ace did. The Jupiter Ace
| definitely has its quirky appeal, meanwhile, as a FORTH Machine -
| but it should be noted that the Oric-1/Atmos machines get far,
| far better software written for them, even today .. and some of
| the new stuff is just great.
| mhandley wrote:
| 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.
| jgrahamc wrote:
| It's great to read a recollection by someone from the UK of a
| similar age to me. I remember the Jupiter Ace very well and was
| so interested in Forth that I got the Acornsoft Forth ROM for
| my BBC Micro. I too made money selling software (and writing
| magazine articles---mostly about the Research Machines
| 380Z/480Z).
|
| I think the biggest difference between then and now is the
| sense of discovery. I spent an enormous amount of time just
| discovering everything I could about computers and the machines
| I had access to. Everything from circuit diagrams to compilers.
| I don't think there's the same level of discovery now because
| so much else is available. In some ways, a lot of what we
| _could_ do with a computer was understand the computer itself
| because other stuff (like games or programs to buy and run) was
| relatively difficult to get.
| mhandley wrote:
| I agree completely about that sense of discovery. No-one
| around me knew anything about computers and the information
| available was limited, but somehow figuring things out for
| myself was a key part of the attraction for me. And it served
| me very well as the foundation for a lifetime of research
| too. If you're passing through London and fancy a beer, look
| me up, and we can reminisce!
| Zeetah wrote:
| Awesome story. Which year did you create the micromouse?
|
| Any change you have pictures of it?
| mhandley wrote:
| The micromouse would have been spring 1983 I think. If there
| were any pictures, they'd probably be in my parents huge pile
| of unindexed old 35mm slides!
| astrobe_ wrote:
| Meanwhile, I managed to roast an EEPROM that contained a
| assembler/disassembler for Z80 by pluging it the wrong way in a
| weird expansion board for a CPC 6128. It was an expensive Xmas
| present, I almost passed out when I realized my mistake. I
| don't remember how old I was when it happened, but definitely
| not enough to RTFM cautiously.
|
| So I had to stick with Basic until I finally got my first PC.
| It was the time when one could order floppy disks preloaded
| with "sharewares" you selected from a catalog. The first and
| only I order contained A86/D86 [2] and PygmyForth [1]. I picked
| up a Forth because I saw ads in magazines for Forth systems
| featuring multitasking and other wonderful things.
|
| I spent a lot of time with those two, and eventually started to
| program my own Forth interpreter as any sane person should
| do... I ended up writing a minimal assembler with the help of
| A86's extensive manual in order to be able to boot my system
| from a floppy, modify its source with a block editor, and
| recompile it from scratch, boot sector included. It's sole use
| ever was to prove myself I could do those "difficult" things.
|
| [1] https://pygmy.utoh.org/pygmyforthmanual.html [2]
| http://eji.com/a86/
| PaulHoule wrote:
| The earliest home computers had tiny amounts of memory: my TRS-80
| Color Computer started out with 4K of RAM and BASIC in ROM
| although within a few years I had it filled out with 64K of RAM.
| There weren't a lot of languages that would fit in 4K, but they
| included BASIC, FORTH and assembler (like the actual assembler.)
| [1]
|
| My FORTH experience with that was writing a subroutine-threaded
| FORTH for the 6809 under the OS-9 operating system in about 3000
| lines of assembler. I wrote to the Forth Interest Group and they
| sent me a card which had a list of standard words in FIG FORTH,
| mine complied with that except that I used the Unix-like system
| calls from OS-9 for file I/O instead of the block scheme most
| FORTHs used.
|
| [1] The popular 6502 (Apple ][, Atari 400/800, C-64, ...) was
| particularly weak in support for compiled languages because it
| had few registers and fewer addressing modes but it was easy to
| write a FORTH for too.
| satiated_grue wrote:
| The 6502's lack of registers is one point of view.
|
| Another point of view is that the zero page provides 256
| registers:
|
| https://spectrum.ieee.org/q-a-with-co-creator-of-the-6502-pr...
|
| "[Bill Mensch]:Rod Orgill and I had completed the designs of a
| few microprocessors before the 6501/6502. In other words, Rod
| and I already knew what was successful in an instruction set.
| And lower cost was key. So we looked at what instructions we
| really needed. And we figured out how to have addressable
| registers by using zero page [the first 256 bytes in RAM]. So
| you can have one byte for the op code and one byte for the
| address, and [the code is compact and fast]. There are
| limitations, but compared to other processors, zero page was a
| big deal."
|
| https://news.ycombinator.com/item?id=38627821
|
| http://forum.6502.org/viewtopic.php?f=2&t=7304
| renewedrebecca wrote:
| I see this idea a lot, but I don't really buy it. I've coded
| in 6502 assembly for years, and the zero page is not
| register-like at all.
|
| Best thing you can say about zero page is that it only
| requires one read cycle to fetch a value from. (Or one write
| cycle to store a value to it.)
|
| Why ZP isn't like registers: You can't do register operations
| with it. For example, you can do this with the accumulator:
|
| LDA #03 ; load immediate value of 3. STA $c000 ; store it at
| $c000.
|
| or
|
| LDA $1004 ; load a value from $1004. ADC $4000 ; add the
| value stored at $4000. STA $4001 ; store to $4001.
|
| You can't do this at all with a zero page address. You have
| to go through an actual register first.
| wduquette wrote:
| I suspect that the Ace would have failed quickly in the market,
| at least as an end-user machine, even if it had matched the ZX
| Spectrum for graphics and memory. It was extremely difficult to
| corrupt memory in BASIC unless one got too eager with POKE; but
| every memory set in Forth is basically a POKE.
|
| Might have been a popular hobbyist machine, though.
| pjmlp wrote:
| There were extensions for the Speccy to use Forth instead of
| BASIC, I remember such ads.
|
| Don't remember if it was ROM replacements, or plugged into
| extension port on the back.
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