Author Topic: A FAIR DEBATE  (Read 121771 times)

Offline ka9q

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Re: A FAIR DEBATE
« Reply #135 on: August 22, 2012, 10:16:26 AM »
So, a sort of saturable reactor/mag amp setup. That is clever...the descriptions I found weren't very detailed, and left the impression that each word had its own address line with an external multiplexer.
There's actually more than one way to make a read-only transformer memory (as I think it's called) and several distinct designs can be found in the Apollo literature. That confused a bunch of us as to which was actually used in the AGC.

I think all were used in various places; e.g., IBM used a different architecture to contain the software for a peripheral controller.

As you point out, the arrangement of the Apollo core rope memory minimized the number of components, and that's highly desirable in hardware designed for space. But this came at significantly increased manufacturing complexity; consider what was required to change a single bit in the memory to correct a software bug. You'd have to unthread an entire sense wire and rethread another one, making the change in just one of the cores it has to traverse. The IBM scheme had a clever book-like structure with pages that were essentially very thin circuit boards that could be individually replaced to change a given word of memory.


Offline cjameshuff

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Re: A FAIR DEBATE
« Reply #136 on: August 22, 2012, 11:04:50 AM »
As you point out, the arrangement of the Apollo core rope memory minimized the number of components, and that's highly desirable in hardware designed for space. But this came at significantly increased manufacturing complexity; consider what was required to change a single bit in the memory to correct a software bug. You'd have to unthread an entire sense wire and rethread another one, making the change in just one of the cores it has to traverse. The IBM scheme had a clever book-like structure with pages that were essentially very thin circuit boards that could be individually replaced to change a given word of memory.

I'm reminded of a IC ROM technology that was already available at the time...you could get custom ROM ICs, written by physically scratching out individual bits on the die. Only worthwhile for small quantities...a mask ROM would be used for mass production. Much easier to work with than core rope, though, once you had the chips in production.

And rewritable magnetic core memory and similar technologies like plated wire and thin film memory continued to get denser and cheaper, and one-time programmable PROMs and UV-erasable EPROMs became commercially available shortly after the first moon landing...core rope didn't stick around long.

Offline bobdude11

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Re: A FAIR DEBATE
« Reply #137 on: August 22, 2012, 03:43:20 PM »
WOW! I feel like an elementary school kid compared to you folks - I have been interested in computers for a long time, but I never experienced any of the older style (having been brought up on modern 'digital' computers (the TRS-80 Model 1, Level 1 being the first). I am going to really have to watch and read to fully understand everything.

Thank you all SO much for the help - I can't wait to learn something new!!!
Robert Clark -
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I am moving to Theory ... everything works in Theory
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Offline ka9q

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Re: A FAIR DEBATE
« Reply #138 on: August 22, 2012, 10:22:56 PM »
I'm reminded of a IC ROM technology that was already available at the time...you could get custom ROM ICs, written by physically scratching out individual bits on the die.
Are you thinking of fusible link PROM, or is this something else I haven't heard of? I was using fusible link PROMs until the late 1970s when UV erasable PROMs took over.

I do know that in the mid 90s Intel developed the ability to program individual chips with unique values with a laser. They used this to implement the infamous Pentium III serial number that triggered so much opposition that they withdrew the feature. (Not that it matters much; modern computers have plenty of unique system-identifying information, starting with network interface addresses.)
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And rewritable magnetic core memory and similar technologies like plated wire and thin film memory continued to get denser and cheaper
Yes. I'm not as familiar with the IBM-developed Launch Vehicle Digital Computer used in the Saturn Instrument Unit, but I get the impression that the program was stored in read/write core. Is that so? It certainly would have made software updates a lot easier than in the AGC, but at the expense of a lower density. Maybe the Saturn was easier to fly than the CSM or LM.
 

Offline cjameshuff

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Re: A FAIR DEBATE
« Reply #139 on: August 22, 2012, 11:50:56 PM »
Are you thinking of fusible link PROM, or is this something else I haven't heard of? I was using fusible link PROMs until the late 1970s when UV erasable PROMs took over.

No, a Sylvania system where technicians went at the die under a microscope and physically scratched out metal traces exposed for that purpose. (There were only 256 bits to worry about...think of a 32x8 array.)

There's not much on it out there...it was probably pretty much immediately superseded by PROMs.


Yes. I'm not as familiar with the IBM-developed Launch Vehicle Digital Computer used in the Saturn Instrument Unit, but I get the impression that the program was stored in read/write core. Is that so? It certainly would have made software updates a lot easier than in the AGC, but at the expense of a lower density. Maybe the Saturn was easier to fly than the CSM or LM.

Don't know. The AGC is the only system I know of that used core rope memory. The Mariner probes may have as well, but I haven't been able to find specific details. I've found references to a Mars lander that never got off the ground that used it...I think the Viking landers used plated wire memory for all their needs.

Normal core memory was more amenable to increases in density than core rope. It requires a core per bit rather than a core per word, but the cores can be much smaller and packed closer together. I wouldn't be surprised if it exceeded core rope in density before being replaced by things like plated wire memory.

Offline ineluki

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Re: A FAIR DEBATE
« Reply #140 on: August 23, 2012, 08:04:55 AM »
That's how I figure reputable actors end up in disreputable movies, too.  We refer to them around here as "grandmother in a basement" movies--someone's got the person's grandmother at gunpoint in a basement somewhere unless whoever-it-is agrees to make a terrible movie.

Sounds more exciting than the probable truth of "Money, Dear Boy".








Offline gillianren

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Re: A FAIR DEBATE
« Reply #141 on: August 23, 2012, 02:01:13 PM »
Sometimes, "money, dear boy" doesn't seem to go anywhere near far enough.
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Offline Echnaton

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Re: A FAIR DEBATE
« Reply #142 on: August 23, 2012, 05:20:16 PM »
I have attributed it, at least in part, to the fact that you can't always tell how a movie will turn out when you sign the contract.  A good partial script can turn in to an awful completed script or the budding young director can turn out to be a hack when given full control of a major film.  Even seasoned directors turn out duds.  It is part of the result of reaching for artistic goals amid the need keep within a budget and reach a broad enough audience.
The sun shone, having no alternative, on the nothing new. —Samuel Beckett

Offline gillianren

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Re: A FAIR DEBATE
« Reply #143 on: August 24, 2012, 02:02:02 AM »
But why do skilled actors keep appearing in Uwe Boll films?
"This sounds like a job for Bipolar Bear . . . but I just can't seem to get out of bed!"

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Offline Tedward

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Re: A FAIR DEBATE
« Reply #144 on: August 24, 2012, 03:29:00 AM »
Sure I heard Michael Cain on one of them TV chat shows and asked why he appeared in a bad film, he said it paid for his mothers new house with a grin. Not the house with a grin Mr Cain said with a grin.

From memory so it might have been Michael York talking about another film...... nah, pretty sure it was that.

Offline Al Johnston

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Re: A FAIR DEBATE
« Reply #145 on: August 24, 2012, 06:59:07 AM »
There was a great line in an episode of Not the Nine O'Clock News:

"Sir John Geilgud has defended his appearance in the film Caligula, saying there was no mention of sex and violence when he read the original paycheque." ;D
"Cheer up!" they said. "It could be worse!" they said.
So I did.
And it was.

Offline ineluki

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Re: A FAIR DEBATE
« Reply #146 on: August 24, 2012, 08:54:46 AM »
Sure I heard Michael Cain on one of them TV chat shows and asked why he appeared in a bad film, he said it paid for his mothers new house with a grin. Not the house with a grin Mr Cain said with a grin.

Probably Michael Caine about Jaws: The Revenge:
"I have never seen the film, but by all accounts it was terrible. However I have seen the house that it built, and it is terrific."

Offline Tedward

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Re: A FAIR DEBATE
« Reply #147 on: August 24, 2012, 09:50:57 AM »
Bit of thinking, it involved bees. Looks like the Swarm, mind you, never seen that Jaws one, maybe it paid for the garage....

Offline gillianren

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Re: A FAIR DEBATE
« Reply #148 on: August 24, 2012, 02:06:15 PM »
I can't think appearing in Uwe Boll films pays for much.  And you have to work with Uwe Boll, which makes it not worth it no matter how much it pays.
"This sounds like a job for Bipolar Bear . . . but I just can't seem to get out of bed!"

"Conspiracy theories are an irresistible labour-saving device in the face of complexity."  --Henry Louis Gates

Offline Tedward

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Re: A FAIR DEBATE
« Reply #149 on: August 25, 2012, 03:24:18 AM »
Had to google him. I just assumed he was a director of no fame yet. I see what you mean. I suppose you cannot fathom every actor.