4 ms·
I particularly liked the description of the HP clock module referenced in the article: >The design of the clock module was rather unusual. To preserve the time
by EvanAnderson 6y ago
I particularly liked the description of the HP clock module referenced in the article:
>The design of the clock module was rather unusual. To preserve the time when the computer was powered-down, the clock module was built around a digital watch chip with a backup battery.17 Inconveniently, the digital watch chip wasn't designed for computer control: it generated 7-segment signals to drive an LED, and it was set through three buttons. To read the time, the Nanoprocessor had to convert the 7-segment display outputs back into digits. And to set the time, the Nanoprocessor had to simulate the right sequence of button presses to advance through the digits.'
That's quite the convoluted bit of interfacing, but no doubt using the off-the-shelf digital watch chip made it a "win". It's pleasingly Rube Goldberg.
- jhallenworld 6y agoI saw some projects in the 70s where they add a math co-processor to a standard 8-bit CPU by interfacing to an off the shelf calculator chip, with all the same issues. I'm sure it would be slower, but maybe the physical size might be the same as the ROM chips (1702s?) that would be required for the floating point code.
- duskwuff 6y agoBack in the 90s, Intel ran a print advertisement for the Intel 387 portraying their competitors' math coprocessors as pocket calculators: https://i.pinimg.com/originals/fd/1d/01/fd1d012149d9e7d67371747a91f69b21.jpg https://i.pinimg.com/originals/fd/1d/01/fd1d012149d9e7d67371... I guess there was something to that? :)
- kens 6y agoThat's an interesting ad, but a bit ironic given Intel's later Pentium floating point division bug. On the topic of using calculator chips as coprocessors, National Semiconductor introduced the MM57109 Number Cruncher Unit (that is the real name) in 1977. It was essentially a repackaged 12-digit scientific calculator chip, operating on binary-coded decimal values with values entered in Reverse Polish Notation. This chip was absurdly slow; a tangent, for instance, could take over a second. http://www.projects.scorchingbay.nz/dokuwiki/_media/electronic/datasheet/national/an-186_mm57109_interface_to_microprocessor.pdf http://www.projects.scorchingbay.nz/dokuwiki/_media/electron...
- SomeoneFromCA 6y agoMakes me think about https://en.wikipedia.org/wiki/Casio_F-91W https://en.wikipedia.org/wiki/Casio_F-91W, "the gitmo watch".
- myself248 6y agoOne of these arrived on my doorstep today. I was realizing that I don't have a decent portable way to tell the time for long periods. Cellphones die in a few days, my AA-powered wall clock is hardly pocket-sized, and I haven't worn a watch in years. Seemed prudent to acquire. I hit up the Casio outlet on eBay, searched "digital alarm" and sorted by price. Bam, F91W. Buy it now, done and done. Then I started reading about its storied history! What a wild ride. If it's good enough for.... literally everyone from Presidents to terrorists... it's good enough for me.
- djmips 6y agoVery much so, it reminded me of when you see some 'clever' code working around some legacy APIs.
- hinkley 6y agoI just broke someone's brain by relating this fact to them. Layers of abstraction, even in the hardware.
- m463 6y agoI remember reading a part in iWoz about a circuit he built with an IC, that he created by ignoring the interface and knowing the internal circuit diagram.