kens

5 ms·

31.
by kens 3mo ago
The short answer is the "14-day" rule, which doesn't allow development of the embryo beyond 14 days. The article gives specifics under the heading "Ethical and legal compliance"
32.
by kens 3mo ago
Oops, I've fixed that now.
33.
by kens 3mo ago
It's unlikely that you'd get a simultaneous tie; you'd expect one computer to go bad before the other. But I think in that case, the astronauts switch to the Backup Flight System, the fifth computer. Mission STS-9 had two com
34.
by kens 3mo ago
There have been a fair number of GPC failures [1], and computers have been voted out. I haven't looked closely enough to see how many were "disagreements" versus hard failures or self-check failures. [1] Search for "GPC&
35.
by kens 3mo ago
Sorry, I don't know anything secret :-)
36.
by kens 3mo ago
I don't know if these boards were flown. They were coated with conformal coating (which I hate for reverse-engineering), which is usually omitted from prototypes. I believe that bodge wires are okay for flight if they are done properly
37.
by kens 3mo ago
Yes, the low density and TTL chips (instead of MOS) helped against radiation. When the Shuttle computers moved to semiconductor RAM, they needed extensive error correction, as well as a process that constantly fixed bit errors, as the memor
38.
by kens 3mo ago
Author here if you have questions...
39.
by kens 4mo ago
What I'm interested in is the best starting word. Using Shannon entropy, the paper finds that it is "tares".
40.
by kens 4mo ago
CAD was a very incremental process. Early chips were drawn by hand and the Rubylith masks were cut by hand with the help of a Coordinatograph. Later, Intel used a Xynetics plotter to cut the Rubylith. By 1974, layouts were digitized with a
41.
by kens 4mo ago
Yes, you can use a "logarithmic shifter". The CDC 6600 supercomputer (1964) used that approach. The tradeoff is that you need more stages with the logarithmic approach (six versus two for 64 bits). If you're using MOS pass tr
42.
by kens 4mo ago
That's a very interesting board! It came out in 1976 (four years before the 8087) and cost $499 assembled, equivalent to $2900 in current dollars, so it was expensive. It was really a decimal processor built from simple TTL parts, and
43.
by kens 4mo ago
I'm here now if anyone has questions. I can't be online all the time :-)
44.
by kens 4mo ago
I score 1%. Is that good or bad? https://www.intheweights.com/p/ken-shirriff
45.
Python dev saved from disaster by intuition and AI(theregister.com)
2 points by kens 4mo ago|0 comments
46.
by kens 4mo ago
On a complete tangent: there's a drawing of an iceberg halfway through the article, the typical vertical shape with 10% above the surface. It turns out that icebergs don't float that way; they rotate until they are mostly horizont
47.
by kens 4mo ago
I don't think you can count PDP-10 things (Internet, BASIC, 8080 emulator) to support the influence of the PDP-11, since they were completely different computers. The PDP-10 was a 36-bit mainframe, while the PDP-11 was a 16-bit minicom
48.
by kens 4mo ago
I'd suggest the Datapoint 2200 as the most influential minicomputer of all time since half of you are using an instruction set based on it and it is largely responsible for the creation of the microprocessor. Now mostly forgotten, the
49.
by kens 4mo ago
Thanks!
50.
by kens 4mo ago
The 8087 has one metal layer, which makes power distribution more challenging. You want to keep power distribution in the metal, so for the most part the pattern is two interdigitated trees for power and ground. There are a few places where
51.
by kens 4mo ago
In more detail, the microcode engine normally executes one micro-instruction per cycle. For addition, the engine is blocked for one extra cycle to give the result time to percolate through the adder. There is some complicated timing within
52.
by kens 4mo ago
I count approximately 2014 transistors (including pull-ups) for the 69-bit adder. Each block of four bits takes approximately 117 transistors.
53.
by kens 4mo ago
Even by the time of the Pentium, they had moved to much more complicated adders like Kogge-Stone. I wrote about it here: https://www.righto.com/2025/01/pentium-carry-lookahead-rever...
54.
by kens 4mo ago
Author here for your 8087 questions. I find adders and ALUs interesting because they are key to the performance of a system and every system implements them differently.
55.
by kens 4mo ago
That was written by Walter Isaacson, who wrote the biography of Steve Jobs.He is a good writer, but that description of a switching power supply is very messed up. You can see the right ideas inside there, struggling to escape.
56.
by kens 4mo ago
Switchers have much smaller transformers because the frequency is much higher, >20 kHz vs 60 Hz. (This is the same reason that avionics use 400 Hz power instead of 60 Hz.)
57.
by kens 4mo ago
Author here. Can you clarify what you consider Holt's innovative power supply accomplishment to be? I spent an excessive amount of time studying Holt's power supply to find out what made it special, but couldn't find anything
58.
by kens 4mo ago
I noticed the same thing. "The fact that billions of consumers already have iPhones" is a hallucination, not a fact. Billions of consumers have Android phones, but that's not the case for iPhones. (Billions of iPhones have be
59.
by kens 4mo ago
Serious question: what is ONG? I assume it's like LNG (liquefied natural gas), but after multiple searches, all I can come up with is Oklahoma Natural Gas, NGO in French, and On God.
60.
by kens 4mo ago
I'd be interested in scanning the drawings if they aren't already scanned. If you want to get rid of the modules, I can set you up with a museum.

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