[HN Gopher] Reverse-engineering a 1960s hybrid flip flop module ...
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Reverse-engineering a 1960s hybrid flip flop module with X-ray CT
scans
Author : zdw
Score : 54 points
Date : 2022-08-05 18:01 UTC (4 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| gumby wrote:
| My dad described using modules like this. Glad to see some
| confirming evidence.
| kens wrote:
| Yes, hybrid modules like this were popular in the 1960s and
| produced by multiple manufacturers. Eventually, of course,
| integrated circuits replaced them for most applications.
| baking wrote:
| Why do you refer to them as "hybrid" modules. Seems like a
| standard transistor logic circuit of the era to me.
| kens wrote:
| That's what they called modules that were built from active
| and passive components. As opposed to a "monolithic"
| integrated circuit.
| NovemberWhiskey wrote:
| Technically, a hybrid integrated circuit is just a bunch of
| individual components that are integrated together into a
| single package vs a monolithic integrated circuit which is
| your typical "everything on a chip of silicon".
| kens wrote:
| Author here for your X-ray questions...
| iasay wrote:
| No questions just appreciation. Your blog and Marc's channel
| are about the most interesting things I've read and watched for
| years (as an ex EE). Pure quality content. Thank you.
| kens wrote:
| Thanks for the nice comment!
| [deleted]
| skywal_l wrote:
| What kind of file format the CT machine produce? DICOM? What's
| the spatial resolution of the model? How big was the file for
| this component? Could you make the file available? Are they
| using webgl to display the volume in 3D?
| kens wrote:
| The system is web-based so I don't know about the underlying
| file format. They've downloaded files to a 3-D printer so
| it's something usable. The spatial resolution depends on the
| size of the object (which determines how close it is to the
| sensor). In one scan we saw the bond wires inside a
| transistor in a unit, so the resolution can be very good. For
| a large, dense metal object the resolution is lower.
|
| This scan is online at: https://app.lumafield.com/project/afa
| 60fd5-308d-41da-a0c6-14... You can manipulate the scan
| yourself after creating an account.
| skywal_l wrote:
| So apparently the volume is loaded in 3 chunks 95MB (285M).
| Looking at the code they are indeed using WebGL (through
| Three.js) for the raytracing. I don't think it's a DICOM
| format, at least not on the frontend side as I don't see
| the usual DICOM fields used in 3D rendering in the code.
| They have multiple versions of React bundled, I don't know
| what's the story about that.
|
| Anyway, thanks for the link, nice piece of technology.
| dreamcompiler wrote:
| > The reverse-engineering solves one mystery about the flip flop
| ... Looking at the reverse-engineered schematic, though, explains
| that a sharp pulse on the J pin will act like the clock, sending
| a pulse through the capacitor, turning off the transistor, and
| causing a high output. I assume this behavior is not intentional,
| and J inputs are expected not to transition as sharply as when I
| touched it with a ground wire.
|
| This paragraph caused chills to run up my spine. The fact that
| they used AC coupling on the clock line seemed clever because it
| saved a couple of transistors, but the fact that they depended on
| J and K always being "slow" was cringeworthy. If J and K were
| somehow not slow, the device would become "not a proper flip
| flop." And yet it went to the Moon, so I guess they knew
| something I don't.
|
| One other thought: When Ken grounded the J line, he was attaching
| it to essentially zero impedance to ground. The clock line will
| never have zero impedance, but it's reasonable to expect it to
| have lower impedance than regular signal lines. The sensitivity
| on J and K might be more a function of signal impedance than
| rise/fall time per se. Of course the two things are not
| unrelated. Potato/potahto.
| kens wrote:
| Good comments. I don't have details on impedance vs fall time
| so I don't know how big the safety margin was. But this
| behavior caused me _so_ much confusion when I was testing the
| module to reverse engineer it.
|
| By the way, this modules wasn't used in flight; it was part of
| a test box that was used on the ground. The Updata Link box
| onboard the spacecraft was built with different technology.
| Just want to avoid confusion :-)
| iasay wrote:
| Fresh out of university as an EE in my first job I was
| surprised to find that the rule was _" if it conforms to the
| tests then it works"_. Sometimes the tests were poorly designed
| or were narrow enough only to test the happy paths. Box ticked,
| ship to customer.
|
| I eventually moved to software at which point I discovered that
| it's even worse here. It's at least 10^6x more difficult to
| kill people though and you usually don't have to get off your
| chair to undo the carnage.
| Aloha wrote:
| Often its "If it _appears_ to pass the test it ships ".
| pixl97 wrote:
| > "if it conforms to the tests then it works".
|
| Um, but what if someone does something outside of the tests.
|
| "Well, then it breaks".
|
| Yes, but this is software, how does it break?
|
| "Hopefully not badly and insecurely"
| [deleted]
| bee_rider wrote:
| Yes in software we don't even have to worry about trying to
| get the magic smoke back into the chip (very difficult).
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(page generated 2022-08-05 23:00 UTC)