What's more interesting than how the calculator works is how Sinclair was able to write the code for such a chip, which the article doesn't attempt to guess at. I wonder if he used some kind of boostrap on paper, looking at the algorithms.
Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
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Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#42What's more interesting than how the calculator works is how Sinclair was able to write the code for such a chip, which the article doesn't attempt to guess at. I wonder if he used some kind of boostrap on paper, looking at the algorithms.
I don't know about the Sinclair development specifically, but for the HP-35, they wrote a register-level simulator in software that let them develop the algorithms and single-step through for debugging. My favorite quote from the article: "Correcting a problem was a simple matter of changing a punched card or two."
http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1972-06.pdf
The article goes into a lot of detail on the HP-35 internals, so it's worth a look.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#43What's more interesting than how the calculator works is how Sinclair was able to write the code for such a chip, which the article doesn't attempt to guess at. I wonder if he used some kind of boostrap on paper, looking at the algorithms.
I don't know about the Sinclair development specifically, but for the HP-35, they wrote a register-level simulator in software that let them develop the algorithms and single-step through for debugging. My favorite quote from the article: "Correcting a problem was a simple matter of changing a punched card or two." http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1972-06.pdf The article goes into a lot of detail on the…
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Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#44I am not sure what is more amazing, the original creation or the cleverness of the person who figured out everything they did. I guess the original creation but wow, now that is a dedicated hobbyist. The Visual 6502 group enjoys dissolving old chips in acid, photographing the die, and reverse-engineering them. Wow!
The Visual 6502 group enjoys dissolving old chips in acid, photographing the die, and reverse-engineering them.
Unfortunately (or not, depending on your perspective) it's not just the Visual 6502 group that enjoys that. Any leading chip in the marketplace these days is almost immediately reverse engineered in this way. I haven't been in the chip business for a few years but I recall a company which offered this as a complete service - they'd send you detailed circuit schematics and so forth.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#45Earlier quoted context omitted.
Yes, that and Apple Writer. Full disclosure: I wrote Apple Writer.
Thank you for writing Apple Writer. 1. I wrote most of my high school reports on it. 2. I once wrote a set of WPL programs to automate the generation of multiple-choice tests, and sold it for $50 to my uncle who was a physics teacher. 3. Apple Writer was the second program I disassembled from beginning to end (the first was Locksmith Fast Disk Copy), learning a lot in the process.
> Thank you for writing Apple Writer.
You're welcome!
I know this is a predictable remark, but I miss the good old days. The Apple II was so simple and understandable that I was able to write a program that played two musical notes at once (I called it the "Electric Duet"), in tune, and a fairly tolerable sound, even though the speaker was driven by a TTL output (meaning no analog level control).
If the Apple II had had interrupts, my program would have stopped working. I know this because an Apple II successor supported a mouse, the mouse required an interrupt, and it ruined the performance of my program.
Oh, I almost forgot -- Tom Clancy wrote "The Hunt for Red October" on Apple Writer.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#46Reverse Polish Notation - sounds like the punch line to a really bad math joke
After I got used to RPN (I had a lovely old HP-21) I found it much more intuitive. Stack-based thinking. No parentheses! (And I've used LISP for years, but that's entirely different.) RPN vs Infix/Algebraic used to be a holy-war topic. Like emacs vs vi, or iPhone vs Android. Once you go RPN, you can never go back again.
I know that feel, bro. ENT > =!
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#47Nicely done, especially compared to the fits that HP went through trying to figure out how they could prove or disprove that all 11 digits of their calculation were correct.
I wouldn't call them "fits", really. 40 years ago these calculators were looked upon with a bit of skepticism. Engineers that were used to seeing the log tables with their own eyes and hand-manipulating slide rules were being asked to trust the results coming out of these calculators. And lives depended on it, really. If you were a civil engineer designing a bridge and you needed to be absolutely sure the numbers you…
A very old school surveying teacher (head of department as it happens) wasn't entirely convinced about calculators in the late eighties. I showed him how to get an extra decimal place of seconds of arc by subtracting the whole number of degrees.
The real sticking point was getting a real arctan2 function (returning the angle in the range [0,360]). He really liked some BBC Basic programs I hacked up. Fun times.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#48I am not sure what is more amazing, the original creation or the cleverness of the person who figured out everything they did. I guess the original creation but wow, now that is a dedicated hobbyist. The Visual 6502 group enjoys dissolving old chips in acid, photographing the die, and reverse-engineering them. Wow!
The Visual 6502 group enjoys dissolving old chips in acid, photographing the die, and reverse-engineering them. Unfortunately (or not, depending on your perspective) it's not just the Visual 6502 group that enjoys that. Any leading chip in the marketplace these days is almost immediately reverse engineered in this way. I haven't been in the chip business for a few years but I recall a company which offered this as a…
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#49Earlier quoted context omitted.
Thank you for writing Apple Writer. 1. I wrote most of my high school reports on it. 2. I once wrote a set of WPL programs to automate the generation of multiple-choice tests, and sold it for $50 to my uncle who was a physics teacher. 3. Apple Writer was the second program I disassembled from beginning to end (the first was Locksmith Fast Disk Copy), learning a lot in the process.
> Thank you for writing Apple Writer. You're welcome! I know this is a predictable remark, but I miss the good old days. The Apple II was so simple and understandable that I was able to write a program that played two musical notes at once (I called it the "Electric Duet"), in tune, and a fairly tolerable sound, even though the speaker was driven by a TTL output (meaning no analog level control). If the Apple II had…
And thank you for writing Electric Duet!
That program inspired me to (cough) take it apart and understand how something so cool could come out of the Apple II's speaker. That exercise taught me 6502 opcodes and I've been working in embedded systems ever since.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#50Unfortunately, as calculator prices collapsed, so did Sinclair Radionics' profits, and the company was broken up in 1979 after heavy losses. He fought Moore's law, and the law won. But this whole thing reminds me of Woz's work in the first Apples. Why wasn't his genius work similarly wiped out? Soon after the Apple, there were dozens - hundreds - of new personal computer manufacturers. I think it's software. The valu…
One unnamed reason for Sinclair Radionics' falling apart was their digital watch, Black Watch, which was the ultimate example of Sinclair's infamous cost cutting and lack of quality control. http://www.nvg.ntnu.no/sinclair/other/blackwatch.htm
Surely also ridiculous diversions such as the C5 electric car.
"Micromen" is a fantastic drama of the period...