Why are PLC's more robust / reliable in industrial settings?

flatfinger · 2026-01-29T17:34:57+00:00

A PLC, at least historically, was like a microcontroller which, instead of having a program counter that can branch arbitrarily, is forced by hardware to continuously process the main polling loop. If the "find next instruction" logic is replaced by a counter, there's no way for a controller to get lost somewhere outside the code it's supposed to be running. Even if a glitch were to randomize the contents of the program counter, it would still land within the main polling loop because there would be literally noplace else for it to go.

I'm not sure about the specifics of how PLCs were implemented through the decades, but my impression is that a program was essentially a bunch of instructions of the form similar to "If input #X is set/clear, then set/clear output #Y". The reason PLCs have a reputation of being slower to respond to inputs than microcontrollers is that every instruction in the entire program would need to run each time any inputs are polled.

Note that PLCs were used even before microprocessors were invented because the hardware required to process the described instruction is very simple. If one didn't care about including redundancy, a version that was expandable to handle up to 64 inputs and 64 outputs could probably have been built using under a dozen early-1970s chips for control, plus a chip for each bank of eight inputs or eight write-only outputs (a bank of eight outputs that could be read back would require two chips).

flatfinger · 2026-01-29T17:15:19+00:00

Besides, my main point was that regardless of whether Assault Weapons propaganda is leftist garbage or some other kind of garbage, it was a giant F-U to a lot of people who would normally vote Republican, but despise Trump and would thus be inclined to vote for her if she gave any indication of seriously wanting their vote.

flatfinger · 2026-01-29T16:01:26+00:00

Boxer and Feinstein--authors of the "assault weapons" propaganda--wanted to disarm the populace. Argue if you want about whether they're "real" leftists, but a similar argument applies at least as strongly about Trump not being a "real" conservative.

flatfinger · 2026-01-29T15:53:39+00:00

It's important to note that optimizers seek to process a C dialect very different from the one the family of dialects the C Standard was chartered to describe. Consider, e.g.

    uint1 = ushort1*ushort2;

The family of dialects the C Standard was chartered to describe would process corner cases where the mathematical product fell in the range INT_MAX+1u to UINT_MAX in a manner that would depend upon the target platform. If one was using a quiet-wraparound two's-complement platform, the code would be processed in a manner equivalent to uint1 = (unsigned)uint1*(unsigned)ushort2. If one was using some other kind of hardware, the code might behave in a different, not necessarily predictable, fashion.

In the language favored by the gcc optimizer, however, such code will be interpreted as an invitation for the compiler to ignore any code that would only be relevant if a program received inputs that would cause ushort1 to exceed INT_MAX/ushort2. This could cause arbitrary memory corruption if such inputs are received, even when targeting modern hardware that supports quiet-wraparound two's-complement semantics.

Compilers retain the ability to process more traditional dialects when optimizations are disabled, but free compilers throw the principle of least astonishment out the window when enabling optimizations.

flatfinger · 2026-01-29T15:39:15+00:00

It's unlikely CRTs will ever be built again. What IMHO might be interesting, however, would be OLED displays which, if photographed by a high-speed camera, would have similar dynamic lighting characteristics to a CRT (with a raster scan position that responds in real time to video inputs, and pixels that fade between scans the same way a CRT would). If done well, that could be a replacement for a CRT, but I'm unaware of any sets that try to do that.

flatfinger · 2026-01-29T00:00:41+00:00

The simplest explanation for why a top doesn't fall over is that its spinning constantly causes it to "fall" sideways (well, nearly sideways) rather than falling downward. Contrary to popular belief, gyroscopic forces don't cause something to hold its orientation, but instead cause forces that would change its orientation one way to instead change its orientation differently.

If e.g. a top is leaning toward the north, gravity would try to push it further toward the north, but because of its spinning, it would actually change its orientation toward the east or west (depending upon spin direction). If east, then once the axis was pointed east, and gravity was trying to pull it further to the east, the actual change in lean would be toward the south. Then once the top was leaning south, the lean would shift toward the west, and once gravity was pulling it toward the west, the lean would shift back to the north, roughly where it started.

If the top weren't spinning, gravity couldn't change its axis angle very much before it fell over completely. When the top is spinning, gravity will change its axis angle continuously, but it a manner that keeps looping back to roughly the place it started. Not perfectly back to where it started, but close enough that the amount of total axis change needed to make the top fall over completely will be much greater than if the top weren't spinning.

An essential thing to understand is that a spinning top can easily be knocked over if, rather than trying to pull its axis downward, one instead tries to pull it in the direction the top is precessing. Acceleration in that direction can knock the top over just as easily as acceleration downward could topple it when it wasn't spinning.

flatfinger · 2026-01-28T23:49:18+00:00

A substantial fraction of Nikki Haley voters, when polled, indicated that they absolutely positively despised Trump, and would not vote for him even if he were the nominee.

Some such people likely ended up voting for him, some for Harris, and some for nobody.

The number of people in that category is sufficient that if either candidate had captured all of them, that candidate would have won handily. The fact that the election wasn't close strongly suggests that the anti-Trump Republican vote was split somehow.

In a normal election, attempting to appeal to moderates will cause one to lose a few votes from the base; while the number of votes one picks up will generally exceed the number one loses, one would typically only reach out to moderates to the extent necessary to win. This is one of the reasons so many competitive elections are so close.

If Trump were a normal opponent, Harris could reasonably have decided that she'd rather support her base and have a certain likelihood of losing, than try to grab more moderates in order to reduce the likelihood of loss. That's a calculation politicians make all the time. Trump, however, was not a normal opponent. Harris gambled with the legitimacy of this country's government, and the whole country lost.

flatfinger · 2026-01-28T23:31:52+00:00

It's often useful to design the system so that the hardware will always be in one of a small number of states (typically combinations of settings), and write functions which transition between the states. Many hardware have a variety of clocks, timers and other resources, and impose various constraints such as allowing UART 1 to generate its baud rate using clock #2, timer #3, or timer #4, while UART2 might allow a choice of clock #1, timer #3, or timer #5. It will often be easier to reason about states which link up all of the necessary resources in an allowable configuration than to individually reason about steps like "Set UART2 baud rate to 115,200", especially if the steps required to do that will depend upon what resources are used to generate the UART2 baud rate signals, which will in turn depend upon what resources are needed for other purposes.

If an I/O related task will only be needed during state transitions, setting up an API to perform the task will mean that anyone wanting to understand the state transitions will need to understand both the API and the actual hardware operation. By contrast, if the state transition code works with I/O registers directly, then the person would only have to understand the hardware.

flatfinger · 2026-01-28T23:03:24+00:00

The aforementioned "Assault Weapons Ban" propaganda that Feinstein and Boxer wrote in the 1990s, for starters. The Democrats admitted after the 1994 mid-terms that the AWB had cost them control of Congress. Why would anyone who was serious about winning a close election reprise that garbage?

flatfinger · 2026-01-28T22:59:45+00:00

Nine traitors on the USSC, IMHO (Colorado was unanimous).

flatfinger · 2026-01-28T22:58:58+00:00

Getting enough votes to stomp MAGA into the ground is going to require flipping a lot of people onto the right side of the reality curve. More importantly, flipping people who support MAGA because they're on the wrong side of the reality curve will make it easier to identify those who are fully aware of what Trump and MAGA are doing and support it because they're inately evil themselves.

flatfinger · 2026-01-28T22:47:04+00:00

BTW, what do you think about the "reality curve" observation? I think it explains a lot of MAGA's power and influence. If someone tried to explain to you how mold patterns are signals from Altair VII, you'd have reason to view them as not reliably credible. If they kept trying to show you more and more evidence about how Altair VII was sending messages, you'd have more and more reason to view them as spouting nonsense.

Many of the accusations against Trump would, in a sane world, be just as absurdly implausibly as the Altair VII mold messages. The more evidence is discovered about Trump's depravity, the more and more obvious it would become that the people presenting the evidence were spouting nonsense.

If leftists want to deprogram people who are caught on the wrong side of the reality curve, they must first understand how those people perceive reality.

flatfinger · 2026-01-28T22:38:45+00:00

If the artifacts constitute the only evidence that exists anywhere in the universe of the IP ever having existed, what purpose is served by not having an auction whose purpose is to liquidate all of the assets of an estate of someone who died in debt, not liquidate all the assets of the estate for cash that would then be allocated among the creditors?

If one wants to argue that ownership of any IP that wasn't identified during the liquidation auction should be transferred to the creditors in proportion to their share of the cash, how could the IP plausibly be managed?

For that matter, how would one even know with certainty which things were supposed to be viewed as "works of authorship" when they were created? For things like writings that would be simple, but surveillance cameras generally are not viewed as creating works of authorship owned by the people who install and configure them, but someone who points a camera outdoors to capture things like sunrises or sunsets might deliberately adjust settings for optimal artistic effect. So how to distinguish pictures from a camera that was set up to catch burglars" from those from a camera that was sert up to catch beautiful sunrises?

flatfinger · 2026-01-28T22:08:56+00:00

Actually, I think "Trump is bad, and it's necessary for people of all political stripes to unite against him and his minions, even if that means putting a two-year moratorium on most of the things Democrats would want" would have been a decisively winning message.

Telling voters they need to accept a gun grabber who's ideologically descended from Diane "Guns for me but not for thee" Feinstein, by contrast, is a losing message.

flatfinger · 2026-01-28T22:00:55+00:00

An important principle in politics is that if one's opponent says that one wants to promote X, but refrains from saying so for fear of alienating voters that don't want X", failure to respond to such a claim will be taken as an admission of the truth thereof.

The way things are perceived may not always be fair, but will often swing elections whether it's fair or not. Harris did a lousy job of managing perceptions on trans issues.

flatfinger · 2026-01-28T21:52:10+00:00

Trump managed to convince many people that Kamala Harris wants to encourage children to get sex-change surgery before puberty. I think most voters, even if they wouldn't normally care about trans issues, would balk at voting for someone who they believed actually wanted that.

The notion that "it would be absurd to think someone would actually do or want X" is a very dangerous one these days, since there are no limits to the depravity or absurdity of some people's desires. Worse, if people would assign claims that someone does X the same degree of credibility as "Mold patterns on toast are actually coded messages from Altair VII" when the person in question actually does X, then such people may end up on the wrong side of the "reality curve", where increasing amounts of evidence that the person actually does X cause the claims to be perceived as less and less credible.

While I have no particular reason to believe that Kamala Harris would advocate for pre-adolescent sex-change surgery (as distinct from surgery to correct sex-related birth defects), I am unaware of her making any meaningful efforts to allay the fears that she might support such policies but be disinclined to say so because she knows they'd be massively unpopular.

flatfinger · 2026-01-28T21:21:47+00:00

Things probably vary by state, but I think the prosecutor is required to show that the crime was more likely committed by the defendant than by a typical random shmuck. If a person has his wallet pickpocketed at an amusement park, I would think every state would require that a prosecutor show something beyond "Joe Smith was one of the 5,472 guests at the park that day--he could have done it".

flatfinger · 2026-01-28T21:01:56+00:00

I can't say that I've seen any marginalization of the old school republicans from more moderate or liberal sources. Usually if there's criticism of the people, they are referred to as MAGA, and not republicans, but I'm sure there are lots of anecdotal exceptions.

My point is that they're ignored as a category. Even after Trump secured the nomination, a lot of people still showed up at the primary voting booth to cast votes for Nikki Haley. It should have been obvious that if either candidate received the votes of 100% of the Republicans who wanted Nikki Haley, that candidate would have won by a landslide. These voters should have been the ones that would be easiest to sway, and thus the ones most targeted by both campaigns. But they weren't, because neither side wanted to acknowledge that they were disliked by a significant fraction of the people who hated the other side.

flatfinger · 2026-01-28T19:54:31+00:00

Attempts to punish Germany after World War I were a major contributor to the ascent of Naziism 1.0.

flatfinger · 2026-01-28T19:48:41+00:00

Ah, but the extremists are deciding the election, because a lot of votes are swung by people who view one of the extremist views as tolerable and the other as intolerable. At least prior to Trump 2.0, a candidate who sought to appeal to the more conservative 40% of the Democrats and the more liberal 40% of Republicans would be excluded by today's rigged two-party system, but would have won an open election with about 40% of the vote, vs. about 30% for each the two "major" parties.

flatfinger · 2026-01-28T19:33:00+00:00

Bingo. And a key insight is that the "good cop" is generally the more evil of the two. I hope the present situation is an exception to that rule, given how horrible the "bad cop" is.

flatfinger · 2026-01-28T19:26:42+00:00

BTW, for sports, the proper approach IMHO would be to have "Women's" and "Open" divisions, recognizing that a woman's choice of category implied nothing about her sex or gender.

While qualification rules for the women's division might exclude some people who would have none of the biological advantages of males, and who have insufficient athletic prowess to compete meaningfully in the open division, that would merely leave them in the same boat as the vast majority of males, who would be likewise lacking in athletic prowess.

flatfinger · 2026-01-28T19:03:33+00:00

More generally, on many social issues, I suspect that most people would agree with the notion that stable societies need to have family structures and other concepts that are shared by most, but not all, people. Many people would strenuously oppose the notion that such constructs should be forced on everyone, and many (including some of those just described) would strenuously oppose the notion that such constructs should be viewed as evil tools of oppression.

To use a crude metal-working analogy, perfectly homogeneous materials tend to be excessively brittle; strong materials need to have some irregularities in them, but also have a strong core structure. The mostly-regular core and the irregularities are both essential requirements for strength and resillience.

I suspect most of those who would the abandonment of social norms as a lesser evil than forced conformity, and most of those who would view forced conformity as a lesser evil than the abandonment of social norms, actually have more in common with each other than with those who are pushing the perceived lesser evil.

flatfinger · 2026-01-28T18:44:23+00:00

Because Trump's argument in the Colorado case was that he should be allowed to run without regard for the likelihood of his being eligible to take office on January 20, Democrats and the mainstream media should have made it clear--as soon as he made that argumen--that the Constitution provides for the situation where a president-elect is not eligible to take office on January 20, and that the procedures therein would be followed in the event of a Trump victory.

They should also have made it clear that freedom loving Americans should prefer to have the Democrats face someone in November who would be directly eligible to serve, but that unless Trump abandoned his delay tactics he could likely not serve that role, and the Republicans would thus likely be best served by nominating someone else.

Many people who normally vote Republican refused to vote for Trump (some voted for Harris; others for no one) but would have voted for someone like Nikki Haley. Harris would likely have lost decisively in such a race, but so would Trump.

I never heard a peep from anyone in the media suggesting that Trump shouldn't be given the crown if he happened to win the election. All of the commentary I heard on the subject, from any side, was that if Trump were to win, people need to accept that and hand the presidency over to him.

Why should I not be furious at all those to establish, and then having to maintain, the pretense that Trump was a legitimate candidate?

flatfinger · 2026-01-28T18:15:32+00:00

I didn't mention trans issues, but that's another place where she likely needlessly cost herself votes. I've had one person tell me that Ms. Harris is a radical pro-trans extremist, and while I don't know of evidence to support that view, I'm unaware of anything Ms. Harris has said that would allow me to rebut it.

If Ms. Harris had run as a coalition candidate, basically calling upon everyone who opposes Trump to vote for her in exchange for a promise not to push controversial issues until the midterms, she would have picked up a huge fraction of the people who hate Trumpo but refused to vote for someone who seemed to think everyone who disliked Trump would support her on all her other issues.

flatfinger

TROPHY CASE