Oh, I've got a good one, people.
It's 1989 and back in those days, I was dabbling with ARM assembler on my new Acorn A3000 with 2MB RAM. This ARM2 based PC beat the pants off the PCs of the day, it was so fast.
ARM assembler was integrated into the BBC BASIC it came with in ROM, so you could write ARM code without loading any apps, quite the unique feature to all Acorn computers since the BBC Micro, perhaps the Atom before it. You just set up a header, memory block, an entry point and away you went. And I loved it. That assembler was so damned fast, too. Anyway, I wrote some small, fast and efficient ARM routine that I felt quite impressed with. Sorry, I forget what it did now after 36 years, but I do remember that I loved programming that elegant RISC processor.
What an awesome architecture, it was like nothing I'd used before it. The only RISC CPUs that existed before it were in high end SUN SPARC workstations of the day that cost many thousands of pounds and totally out of the reach of mere mortals like me. My A3000 was "just" £749, not a small amount by any means, but affordable for the masses, more or less.
That week, I went to the computer club, clutching the floppy disc I'd saved it on with the intention of impressing the resident genius programmer there. And I mean, this guy was
really clever, perhaps even an actual genius, but he was never big headed about it, being one of the nicest people you could meet, always helping out lesser mortals like me and was very sociable. He didn't fit the nerdy socially awkward stereotype at all. I do remember that he was unusually tall and skinny though, towering over everyone in the room. I'll call him Dave, not his real name.
I proudly ran the BASIC program which assembled and ran the machine code and...
It bombed out with some stupid, fucking, error and no way would it work!
It was borked, good and proper.
I started troubleshooting it. The program wasn't corrupted due to a bad disc and his Acorn Archimedes 310 with 4MB RAM wasn't faulty either. No, something was wrong with my program, but
what???! I spent most of that evening hogging poor Dave's Archimedes trying to find the bug in it that caused this crash, but no dice. He eventually wanted his computer back to do the stuff that he'd brought it over for, something really clever, naturally. Thankfully he was nice about it and didn't humiliate me about this cockup, although I was there already, believe me, and extremely frustrated. Heck, I still feel it now when I think about it. He offered to help troubleshoot it for me, but my pride got in the way, so I'd find it or nothing.
I got nothing.
The code looked just fine and I left that meet really frustrated.
At this point dear reader, do you have an inkling of where the problem was yet?
There's a clue in the preceding description.
Right, so I got home, put the floppy disc in my A3000 and lo and behold it worked again! Fixed!
No, of course not as I hadn't modified that code on the disc at all. For good measure, I even loaded the original off the original floppy disc, but the code was identical.
I kept looking and looking and
looking at that program, the whole code, including the BASIC setup section and then it
finally dawned on me: his PC had 4MB RAM while mine had 2MB. This meant that the memory page size in the TLB on his was double the size of mine, but that still shouldn't have caused a problem. There was nothing wrong with the assembly code. What was borked was the header setup for it in the BASIC part. Somehow, I'd made a tiny syntax error in it which resulted in valid BASIC code so there was no runtime error from the interpreter, but scrambled the memory allocation for the machine code, which somehow still happened to work on a 2MB machine, but not a 4MB one.
It was a real simple typo too, like transposing a couple of characters, which I fixed. Again, I don't remember the details after all this time
I eventually upgraded my A3000 to 4MB, the maximum possible, and yes, the fixed program worked while the original didn't, confirming my diagnosis.
Unfortunately, I never got to demo my program to Dave as he didn't always bring his PC down to the club and I wasn't always there, either. I did describe what the code did though and he did think it was decent. Remember, there was no internet, no websites and no email back then. These only existed in a primitive form still being developed in universities and military labs.
I still have that computer and likely the floppy discs I'd stored that program on. Whether those discs still work is another matter though. The power supply likely needs recapping by now, too. It's not been switched on for years.
I didn't have a HDD at the time as they were an expensive luxury back then, so everything was on floppy discs. Unthinkable now in the days of superfast M.2 SSDs, eh?
This is my Acorn A3000:
en.wikipedia.org
