kens

7 ms·

61.
by kens 4mo ago
Univac had similar single-tube modules (but without the handle), as well as multiple-tube modules. See this video: https://www.youtube.com/watch?v=NVbjXHR6WAY The BRLESC computer used printed-circuit boards that had compone
62.
by kens 4mo ago
I don't have the information for the 604, but the 605 used about 36 different types of tube modules. IBM couldn't resist making different types of modules; the 650 had sixteen types of cathode followers alone.
63.
by kens 4mo ago
I powered up the module independently, powering a light bulb, so it's a non-computing configuration. (I'm not sure if that's what you're asking.)
64.
by kens 4mo ago
Nice summary! For anyone interested in these systems, the book "IBM's Early Computers" provides a detailed history.
65.
by kens 4mo ago
One way they get away with using relatively few tubes is that most of the Boolean logic is done with semiconductor (germanium) diodes, using tubes to amplify the results.
66.
by kens 4mo ago
Author here for your vacuum tube questions...
67.
by kens 4mo ago
I've been looking at the 8087 NaN circuitry lately. Having 2^53 (or whatever) values for NaN was supposedly a feature: "the large number of NAN values that are available, provide the sophisticated programmer with a tool that can b
68.
by kens 4mo ago
Thanks for the nice comment!
69.
by kens 4mo ago
That's basically the RISC approach, using simple one-clock instructions instead of complex microcoded instructions. In the case of the 8087, it made sense to use microcode because the 8087 is running in parallel with the regular 8086 p
70.
by kens 4mo ago
Usually, it's not worth the effort of converting microcode into discrete logic to get performance. Among other things, it's a mess to try to fix a bug. A few exceptions: The different models of the IBM System/360 mainframe ar
71.
by kens 4mo ago
Author here if anyone has questions about the 8087's microcode...
72.
by kens 5mo ago
I don't know what the clock speed was, but it performed about 525,000 addition instructions per second. (1.9µs addition time)
73.
by kens 5mo ago
I don't want to be rude, but I am not following your argument here. a) The computer that I'm examining is from 1980, not 1970, so I don't know why you're changing the time period. b) I have the circuit boards in front of
74.
by kens 5mo ago
Why do you doubt that these are multi-layer boards? IBM was making four-layer boards exactly like these in 1964 for the System/360 (signals on the top and bottom layers, power and ground in the middle layers).
75.
by kens 5mo ago
Much of the software was in a language called HAL/S (High-order Assembly Language/Shuttle), using an IBM 360/370 for compilation. Other software was written in Fortran. See https://www.cs.toronto.edu/XPL/
76.
by kens 5mo ago
You can see how the traces go between the holes if you zoom in on this photo: https://static.righto.com/images/cimsa/board-back.jpg
77.
by kens 5mo ago
You're right; I should have said x86-style.
78.
by kens 5mo ago
The Mitra 125 had memory segmentation. It seems similar to the 8086, with descriptors that specified base address and length for a segment. Accessing memory outside a segment caused a trap.
79.
by kens 5mo ago
The grid is 0.1" holes because that's the spacing of most components; it's a bit like perfboard. If you're asking why they used a grid instead of a normal-style PCB, I'm not sure. It probably makes manufacturing the
80.
by kens 5mo ago
Author here if anyone has questions...
81.
by kens 5mo ago
I'm calling urban legend on the story of an IBM 360 catching fire from an illegal opcode.
82.
by kens 5mo ago
That claim is from NASA: https://www3.nasa.gov/centers/kennedy/pdf/566250main_SHUTTLE...
83.
by kens 5mo ago
Yes. The statement in Chip War , like many others, is close to correct but still wrong. When a book gets many things wrong in an area that I know, it makes me worry about its accuracy in areas that I don't know. (See Gell-Mann Amnesia
84.
by kens 5mo ago
Chip War is an interesting book, but it has a lot of errors, which made it frustrating to read. For instance, it said that vacuum tube computers were hardly usable because they attracted moths, so they required constant debugging and were
85.
by kens 5mo ago
Is the ASML machine actually the world's most complex machine under some metric, or is this a claim that someone made up? I.e., did someone actually compare the ASML machine to the Space Shuttle, LHC, Internet, and so forth and show th
86.
by kens 6mo ago
A compass doesn't work well in polar regions, e.g., if you're flying from the US to the Soviet Union.
87.
by kens 6mo ago
The B-52 star tracker used a gyroscope to determine vertical. The Astro Tracker was stabilized by a bunch of motors and synchros so it matched the gyroscope. Thus, the Astro Tracker was a stable platform even as the aircraft pitched and rol
88.
by kens 6mo ago
If you're looking for more, the book "Between Human and Machine: Feedback, Control, and Computing before Cybernetics" is a detailed history of the development of electromechanical fire control computers and feedback systems.
89.
by kens 6mo ago
Maybe at some point. The main problem is that writing a book would require me to focus on one topic, which doesn't seem likely.
90.
by kens 6mo ago
Yes, haze and clouds were a problem at low altitudes, but most of the time the aircraft was above the clouds. The Aurora Borealis (northern lights) was potentially a problem; the system included an aurora filter.

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