6 ms·

The parallel port was great for simple bit-bash interfacing and I miss being able to do such hacking on contemporary PCs. I remember fondly a hacking war story

The parallel port was great for simple bit-bash interfacing and I miss being able to do such hacking on contemporary PCs. I remember fondly a hacking war story from the late 80s. I had just purchased a Mephisto 68000 dedicated chess computer for my own recreational enjoyment. The embedded dev lab where I worked won a new contract and the hardware dudes decided a 68000 was the way to go. Not content to wait weeks, maybe months for first hardware, I decided to get some early experience by hacking at my chess computer. Basically I opened it up, reverse engineered the keyboard scanning hardware (which was implemented with standard jellybean CMOS logic), and commandeered a couple of inputs and outputs for my own purposes. I hooked these up to the printer port of my PC. Then I worked out a simple serial bit twiddling scheme to exchange bytes a bit at a time and coded it up in C as a kind of software serial port. On the PC side I ended up with something that looked just like a simple terminal that happened to talk out the printer port. On the Mephisto side, I replaced the 64K byte EPROM with a 128K byte EPROM. I changed the cold boot vector to point at "my" 64K, which first checked to see if the printer port was hooked up. If it was hooked up, then the CPU stayed in "my" area and ran a monitor I had coded up for the occasion. If it wasn't hooked up it vectored back to the original boot code and the chess computer worked as well as it ever did. I layered a loader on top of everything and enjoyed loading simple cross compiled C programs on my new 68K computer, (complete with 16K RAM).

gozur88 10y ago
The best part of this is you were able to do all that without losing your chess computer. I miss those days as well. It's a lot easier to repurpose things made out of through-hole mounted 7400 series logic than all the custom surface mounted stuff you see today. On the flip side, though, back then to make your own boards you had to shell out thousands of dollars for the software and more thousands for a prototype run.
- billforsternz 10y ago
  Indeed. As a software guy I was sufficiently proud of my hardware effort that I neatly organised everything as a flying lead coming out of the Mephisto complete with strain relief and a tidy professional looking connector. Not as good as a mounting the connector flush somehow, but pretty good for me. It's still in my cupboard and it still worked well (as a chess computer) last time I tried it, although after 25+ years I wonder whether the EPROM is due to start shedding bits. Trying it out as a 68K dev board is more problematic - for reasons discussed in the main article - occasionally I consider having a go but these days I usually find life is too short for those sorts of things.
  - fit2rule 10y ago
    Great story! The rejuvenation of your EPROM sounds like a job for a Bus Pirate! https://en.wikipedia.org/wiki/Bus_Pirate https://en.wikipedia.org/wiki/Bus_Pirate
lokedhs 10y ago
That's really neat, and one of those things I wish I was able to do. I would probably just have gone out and bought an Atari ST just to get my hands on an actual computer with an M68k. It does make me wonder what made you go all of this instead of doing that? It obviously wasn't just your need to program on an M68k. I think you are more of a hardware genius than you want to let on. Either that or you are just good at everything.
- billforsternz 10y ago
  I think back in the day it was normal for an average young embedded software dev like myself to know my way around the basics of digital hardware. Nothing unusual about it then, maybe a little different now? Not sure. As for buying an Atari ST, it would have been quite a big purchase for me at the time. I am in New Zealand, I was probably making about $NZ30K from memory, and a computer like that would have been maybe $NZ1.5K (probably at least double whatever it cost in the US). The age of ubiquitous, super cheap consumer electronics hadn't yet arrived, especially in NZ.
  - fit2rule 10y ago
    >Nothing unusual about it then, maybe a little different now? Not sure. Like you, I cut my teeth in the 80's .. never trust a coder with a screwdriver, amiright .. but it seems that a rejuvenation of this ethos is upon us, with the Arduino and Maker crowd producing plenty of young developers who know how to burn their fingers ..
billforsternz 10y ago
There is an amusing sequel to this story actually, and no harm in telling the story after all these years. The 68K product was a proprietary networking card for a private telephone exchange type product made by Philips. After developing the product in NZ a hardware guy and I were sent to the Netherlands for final testing and further integration prior to manufacture. The Dutch engineers were very well trained and competent, but used to hugely elaborate heavy process and the more free-wheeling type of development we were used to was definitely foreign territory. Rumours that the crazy guy from New Zealand had developed the telephone switch software in his chess computer (i.e. now that I've explained the story, false rumours) preceded our arrival. Now I was young and dumb at the time, and I had decided for some reason to jokingly call the simple bit bashing communication protocol I'd invented to talk to my chess computer "V.69" (The V series protocols - eg V.24 = RS-232 in the USA were big at the time). A V.69 port had actually made it into the final schematics for our board. It was just 5 logic level pins (two inputs two outputs plus ground) - and in production it would not have any impact - but it was possible to solder a 5 pin header onto the pins, and hook it up to a PC running the same terminal software previously discussed - If such a PC was connected my embedded code would emit diagnostic information. We had many meetings during our visit, with the typically gruff non-nonsense Dutch engineers and their huge vats of extraordinarily strong coffee. One of them was with "the Standards guy" who wanted to audit compliance to all possible standards - I was able to spectate mainly as it was hardware stuff. But suddenly he was pointing at the V.69 connector, clearly labelled as such. We'd forgotten all about it. Us> "Oh well, arrrgh, yes. It's a diagnostic port - for the lab only - no impact on production - the header is just omitted." Him> "But what is this V.69 standard?". Us (hopefully)> "Well, it's just a 5v serial diagnostics standard". Him> "Okay, yes I've heard of it". So as is often the case, the need to save face saved the day.
- ragix 10y ago
  Hrmm, small world I work for a small company in NZ that used to be part of the post office, telecom and now we're privately owned. We repair Telco equipment. I am sure one of our PABX guys would be familiar with the Philips PABX. I am on the transmission team so it's not really something I would have seen. We still have a fots and rn64 though!

gozur88 10y ago

The best part of this is you were able to do all that without losing your chess computer. I miss those days as well. It's a lot easier to repurpose things made out of through-hole mounted 7400 series logic than all the custom surface mounted stuff you see today. On the flip side, though, back then to make your own boards you had to shell out thousands of dollars for the software and more thousands for a prototype run.

billforsternz 10y ago
Indeed. As a software guy I was sufficiently proud of my hardware effort that I neatly organised everything as a flying lead coming out of the Mephisto complete with strain relief and a tidy professional looking connector. Not as good as a mounting the connector flush somehow, but pretty good for me. It's still in my cupboard and it still worked well (as a chess computer) last time I tried it, although after 25+ years I wonder whether the EPROM is due to start shedding bits. Trying it out as a 68K dev board is more problematic - for reasons discussed in the main article - occasionally I consider having a go but these days I usually find life is too short for those sorts of things.
- fit2rule 10y ago
  Great story! The rejuvenation of your EPROM sounds like a job for a Bus Pirate! https://en.wikipedia.org/wiki/Bus_Pirate https://en.wikipedia.org/wiki/Bus_Pirate

lokedhs 10y ago

That's really neat, and one of those things I wish I was able to do. I would probably just have gone out and bought an Atari ST just to get my hands on an actual computer with an M68k. It does make me wonder what made you go all of this instead of doing that? It obviously wasn't just your need to program on an M68k. I think you are more of a hardware genius than you want to let on. Either that or you are just good at everything.

billforsternz 10y ago
I think back in the day it was normal for an average young embedded software dev like myself to know my way around the basics of digital hardware. Nothing unusual about it then, maybe a little different now? Not sure. As for buying an Atari ST, it would have been quite a big purchase for me at the time. I am in New Zealand, I was probably making about $NZ30K from memory, and a computer like that would have been maybe $NZ1.5K (probably at least double whatever it cost in the US). The age of ubiquitous, super cheap consumer electronics hadn't yet arrived, especially in NZ.
- fit2rule 10y ago
  >Nothing unusual about it then, maybe a little different now? Not sure. Like you, I cut my teeth in the 80's .. never trust a coder with a screwdriver, amiright .. but it seems that a rejuvenation of this ethos is upon us, with the Arduino and Maker crowd producing plenty of young developers who know how to burn their fingers ..

billforsternz 10y ago

There is an amusing sequel to this story actually, and no harm in telling the story after all these years. The 68K product was a proprietary networking card for a private telephone exchange type product made by Philips. After developing the product in NZ a hardware guy and I were sent to the Netherlands for final testing and further integration prior to manufacture. The Dutch engineers were very well trained and competent, but used to hugely elaborate heavy process and the more free-wheeling type of development we were used to was definitely foreign territory. Rumours that the crazy guy from New Zealand had developed the telephone switch software in his chess computer (i.e. now that I've explained the story, false rumours) preceded our arrival. Now I was young and dumb at the time, and I had decided for some reason to jokingly call the simple bit bashing communication protocol I'd invented to talk to my chess computer "V.69" (The V series protocols - eg V.24 = RS-232 in the USA were big at the time). A V.69 port had actually made it into the final schematics for our board. It was just 5 logic level pins (two inputs two outputs plus ground) - and in production it would not have any impact - but it was possible to solder a 5 pin header onto the pins, and hook it up to a PC running the same terminal software previously discussed - If such a PC was connected my embedded code would emit diagnostic information. We had many meetings during our visit, with the typically gruff non-nonsense Dutch engineers and their huge vats of extraordinarily strong coffee. One of them was with "the Standards guy" who wanted to audit compliance to all possible standards - I was able to spectate mainly as it was hardware stuff. But suddenly he was pointing at the V.69 connector, clearly labelled as such. We'd forgotten all about it. Us> "Oh well, arrrgh, yes. It's a diagnostic port - for the lab only - no impact on production - the header is just omitted." Him> "But what is this V.69 standard?". Us (hopefully)> "Well, it's just a 5v serial diagnostics standard". Him> "Okay, yes I've heard of it". So as is often the case, the need to save face saved the day.

ragix 10y ago
Hrmm, small world I work for a small company in NZ that used to be part of the post office, telecom and now we're privately owned. We repair Telco equipment. I am sure one of our PABX guys would be familiar with the Philips PABX. I am on the transmission team so it's not really something I would have seen. We still have a fots and rn64 though!