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
#2Nicely 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.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#3Nicely 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 were using were accurate to 7 places and totally correct, would you suddenly put all your faith in this small brown box with no way to examine the inner workings?
HP went through a lot to build that trust and it was rightly earned. HP's reputation for building solid accurate calculators kept that business going for decades to come.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#4The bit that is probably most striking to modern eyes is the data representation. With 320 instructions there's simply no room for the "obvious" code to translate to and from a display representation. So everything was stored in BCD and operated on one (decimal!) digit at a time using a 4-bit ALU.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#5The bit that is probably most striking to modern eyes is the data representation. With 320 instructions there's simply no room for the "obvious" code to translate to and from a display representation. So everything was stored in BCD and operated on one (decimal!) digit at a time using a 4-bit ALU.
I was under the impression that BCD was commonly used in calculators. I know that my HP 48 used BCD and was able to address 4 bit nibbles.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#6I 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!
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#7This is great.
Scientific calculators usually provide constants such as e and π but there was no space in the ROM for these constants. The Sinclair Scientific used the brilliant solution of printing the constants on the calculator's case
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#8I 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!
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Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#9This is great. Scientific calculators usually provide constants such as e and π but there was no space in the ROM for these constants. The Sinclair Scientific used the brilliant solution of printing the constants on the calculator's case
That's gotta be the hackiest hack ever - write it on the outside. Genius.
Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
#10Reverse Polish Notation - sounds like the punch line to a really bad math joke