I've been playing around a bit with the HP-75C. I received a replacement battery pack, which takes AAA NiMH batteries. I'm disappointed that it doesn't seem to power the computer. I haven't investigated the matter further, I've been using the wall wart instead. Previously, the wall wart wouldn't power the computer with the original NiCad pack in place. It does work on the wall wart with the AAAs installed, so I'm not sure what's going on. I haven't put a meter on it yet. It hasn't stopped me from playing around with it.
Yesterday I did a little comparison between the HP-75, HP-71 and a TI-74 BASICALC calculator. The TI is roughly contemporaneous with the two HPs, appearing in 1984. I wrote a little BASIC program to sum the digits from 1 to 100, displaying each intermediate result. The HP-75 chugged along at a pace where I could view each result and register what the number was before the next one appeared. The HP-71 was positively glacial, which surprised me. The TI blew through the program so fast I had to add a PAUSE statement at the end to see the total!
That prompted a digression down a processor history rabbit-hole. Apparently it's been well known since the beginning that the HP-75 was faster in many respects than the HP-71. It has a genuine 8-bit cpu designed as a general purpose digital computer. The processor in the HP-71 is the Saturn, a 4-bit calculator chip, which went on to serve in various HP calculators up through the HP-50 (2006), and lives on today in emulated form, vastly faster, in the HP Prime on an ARM Cortex processor. The TI uses a TI cpu, the TMS70C46. I don't know if it went on to any other products. TI used the Motorola 68000 in its later TI-92 calculator, and a Z-80 in the TI-89.
I thought I was pretty much over my calculator obsession, but the HP-75 seems to have re-ignited it. I've since bought some more old crap I'm unlikely to ever need.
So that was the topic of this morning's walking reflection. I haven't really needed a calculator since the Naval Academy. At least, nothing more than a standard 4-function handheld, and seldom not even that, since I do most of those things in my head unless it's a long chain. At Annapolis, I had a TI-56(?), something below the 59, no card reader. It was programmable with a modest number of steps. I recall I only programmed it a few times, mostly for working homework problems quickly where I could check the answers against those in the back of the book. Mostly it replaced log and trig tables.
Some mids had HP calculators with their bizarre "reverse Polish notation." Most of us had TIs though. I think they were more affordable and I know they were available in the Midshipman Store. I don't remember if HPs were carried. The HPs looked as different as they operated, green and tan versus TI's black. The HPs seemed to have better keys though, and that huge ENTER key.
After I was commissioned, I went on to some Navy schools, one for Combat Information Center Officer, and there we were introduced to the HP-67/97 and the Navy's "tactical program library." We got to play around with them a bit and they seemed exotic to me, a little exciting. I don't think we had one aboard GLOVER when I was CICO.
When I went to ASW school, we played around with the HPs again, and a Sharp handheld computer that was intended to replace the HPs. It had a little micro-cassette drive and thermal printer. We used them for "target motion analysis." You'd enter a series of passive bearings from a sonar contact into a program, alter course and enter some more. The handheld would output the data that defined an ellipse, where the target was likely to be. You could then have your helo fly out to search that area. Pretty cool stuff. We did have the Sharp handheld onboard, but we never seemed to use it, not having a towed array.
TMA later became hot again with the introduction of the Harpoon and later Tomahawk over-the-horizon anti-ship missiles. How do you target a weapon beyond active sensor range? By plotting electromagnetic emission intercepts. HF comms, mainly.
We did have an HP 9830 "calculator" aboard GLOVER for deployment. Ships that didn't have Naval Tactical Data System computers could receive a teletype broadcast of link track data that was human-readable, and plot the information on a plexiglass "vertical plot" using grease pencils. It was definitely non-real time, and when there were a lot of tracks the poor Operations Specialist who had to do the plotting was quickly task saturated. The HP 9830 received the teletype signal from radio central and ran a program called ECLIPS, which I think stood for "electronic calculator link processing system," which could parse the Link 14 messages and display them on a miniature vertical plot on a small CRT without getting task saturated. I can't say it was ever terribly useful, but I thought it was cool.
It seems I developed a certain fascination with HP products along the way, although I couldn't afford any back then.
I finally bought an HP-41CV in 1983 or 84 when I was on shore duty and badly managing my money. I still have it, it's in the drawer next to me. I learned enough RPN to use it, and played with a few programs; but it hasn't been of much real use in all the time I've owned it. Still think it's pretty cool though, and it still works too.
Scratching old itches. I guess that's what I'm doing these days. Gets expensive.
Originally posted at Nice Marmot 08:06 Saturday, 12 August 2023