Magnetic Core Memory
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- Опубліковано 9 вер 2017
- Dave looks at a magnetic ferrite core memory board from 1970
Where the data is stored in individual minute ferrite toroidal rings.
Extracted from Mailbag #648 because it wasn't easy to find on UA-cam search. - Наука та технологія
Don't write to it until you read it out!!! It's non-volatile so whatever was stored in the 1970's is still there.
its from a missing apollo mission
Aliens ?? 🤪
@@ronaldbrown9638 no, and also all Data On There is Non Existent
Reading it will erase it. You have to re-write what you read to restore what is in it!
@@Derpy1969 what if it was never read? But then again it is old
Omg, Please make a video where you actually get it running and save some data to it! I would love to see that.
Dave, just rustle up some sense amplifiers and hook it up to your TRS-80 Color Computer through the expansion port, which it will then boot from.The Color Computer's clock of just under 1MHz should match nicely with your 1us prediction for the memory core access speed.
Some assembly (code) required :)
No worries!
Zylon FPV arduino and a bunch of flip-flops?
gerge s- I thought the "color computer" was a Commodore, maybe a 6809 chip.
+Rick Noah the TRS-80 Color Computer (Coco) did have a Motorola 6509 processor, like the Commodore 64, but it wasn't from Commodore and instead it came from Tandy Radio Shack.
And apart from using the same processor it wasn't otherwise related to Commodore's somewhat contemporary Commodore 64, except for running, like most home micros at the time, a version of Microsoft ROM Basic. For the Cocos was this Color Basic for the lower end and earlier models and Extended Color Basic for the higher end and later 64kb versions. The Extended Color Basic ones also had Color Basic ROMs as well and I believe you could use either, although it has been a _long_ while since I have used my old 64kb Coco II.
The Coco came out some years earlier than the C64. The C64 was a somewhat more able machine, although I'm sure that people will argue the toss over this as they did at the time. But there is no arguing that the out of the box graphics modes and sound support were slightly superior in the C64, especially the native graphics modes.
Strangely although the Tandy TRS-80 Color Computer line was called "TRS-80" they were actually unrelated to TRS-80 Model I and Model II, which were released even earlier and which were monochrome machines based around the more expensive Zilog Z-80 processor. Instead of having an output to connect to a TV antenna jack like the Coco did they instead had their own custom monitors and had yet another version of Basic. They also I believe came with floppy disc drives as standard and were much more expensive being aimed at business. They were never as popular as the Cocos.
Almost, the Coco used the 6809, which was a different processor from the C64's 6510 (which was in turn a slightly modified 6502, the more well known variant). The two chips were different manufacturers and not at all compatible.
I worked for a memory company in the late 70's. We were putting 64KB on a 15"x15" board. These boards ran close to $4-5,000.
The wires were attached to very thin but long needles. You threaded the needles through the cores much like sewing. It was all done by hand since there were no robots at the time which could do the job. One memory board took several hours to weave.
The memory had three types of cycles. Read, which also wrote the data back. write which still did a read to clear the location. Read modify write which read the data, let the processor do something with it then write the data back.
5000 usd ? Holy crap !
Interesting, but somehow i see a comparison with a qbit...
@@balajiLILG Yes, they actually paid Americans a living wage to do so-called menial work like that. I have samples of VLSI military parts that cost the US taxpayer 4,000 in 1978 dollars. Those were hand wired with solid gold wire from the die to the external connection.
@@mrmeval6982 Why solid gold instead of copper ? Couldn't they just coat them with something like even Dave's board seems to have on it ? And wouldn't solid gold be more fragile than copper wire since it's softer ? I'd love to see some pictures if you have them on a site too.
@@phoenixsmith4001 Gold doesn't oxidise, which could vary signal integrity. Gold was tons cheaper back then. This was bleeeeding edge tech at the time, so no expense spared.
My source at IBM said these were hand woven. He started his career when these were in use.
The company I currently work for (Ball Aerospace) used to make the magnetic core memories for the space shuttle flight computers. There are still techs employed that used to wire those memory cells by hand.
Thank you so much for taking the time to do this video. One of the original patent-holders was my Grandfather and he passed away this last April... Im an electrician by trade and was pouring over the schematic trying to understand and you explaining it out was a wonderful experience. Thank you.
I always wondered if the magnetic charge could be seen though one of those green magnetic visualizer sheets. If so, you could save a bw bitmap in those beads and actually visualize if though the the green foil thingy or do an animation or something.
I have not tried that but doubt you would see any change in the sheet as the magnetic field is circular and contained within the core. Worth a try though.
That brings back memories. I remember working on an old mainframe that still used core memory in the 80's! How many people figured out that the loops easily visible at the 1:38 mark were designed to provide timing delays.
Made a 64 bit core memory from scratch a couple of years ago. One of the coolest things is writing new data in the same operation as reading the old... and erasing it with a magnet.
Brek Martin
Morning, mate. ;)
(or afternoon? lol)
I know this comment is from 6 years ago, but if you have any resources for where I might learn more about making one could you send those my way?
@@bonefishjr6835My channel. Pretty average video recording then, and it wasn’t exactly a “how to”, but it’s there.
Fantastic! I worked on an IBM 360/67 in college. Same deal, 512K of ferrite core memory in huge cabinets. VM to 1 megabyte for your job if you wanted. These computers cost millions and took up an entire room.
Remember when memory cost $7,500,000 per gigabyte? I do :-) ua-cam.com/video/_yp6jtpQ5fc/v-deo.html
I know it was $950.00 to upgrade my 1984 original 128K Macintosh to 512K.
And never forget that Bill Gates said nobody would ever need more than 640K of RAM. At the time, that made sense because we had started out with 16K!
I thought it was IBM that insisted upon the limit, also IBM forced Intel to create the 8088 with an 8 bit bus, since "No one will ever need a 16 bit bus"...
IBM may have been the reason, but it was Gates who said that.
Your reference says he said he thought it would be enough for 10 years.
Take an array of LED's and get them to respond to the bit of info. You could then see visually what it's doing. You can create an ASCII picture on each panel and have it show without printing it out. Then frame it. Another idea was to have magnet paper over top and watch the beads respond to which bit is assigned.
A real work of Electronics art you can actually see and appreciate. Would be a splendid idea to frame, wall mount as the heart and soul that went into these boards can be really felt. This has really made my day seeing it, thanks.
I have a few of these myself, and the plan is indeed to frame them. I have one from the US (Univac, with a Pentagon stamp, so we know where that came from!), one from the ol' USSR, and another one made in Ireland of all places. They are beautiful things. You can see some artsy-fartsy photos I took of my collection here: imgur.com/a/rvkUL
'destructive' memory, which is why it has both a sense wire which would flip the bits, and an inhibit wire which would 'hold' the memory along with the x/y addressing wires.
Hi Dave
That brings back some old ,days. I used to work on core store memory systems.
You are quite right, reading is destructive. What would normally happen is a read would involve a write to see if the core changed state, then you would do another write to set it back to its original state. In order to change the state of the core both the X and Y lines need to be activated. This is where the inhibit line comes in, it is usually in parallel with the X line. Current is passed through the inhibit in the opposite direction in order to cancel out the X line (both X and Y need to be active to set the state of the core). Where it comes into its own is when you have a bank of say 8 or 16 of these in parallel and you need to write a bit then the inhibit would be enabled on all but the bit you wanted to write.
Anyway I hope I was not telling you something you already know but it is a very interesting bit of history.
Thanks for the video.
ur smart
He probably does, but the rest of us don't. Thanks for sharing.
Modern day Dram, which is capacitor based, is also destructive on reads. There's a buffer on each memory chip that writes the data back after it's been destroyed.
Why would you use this magnetic memory if you could just use the memory in those chips?
Technically core memory is write-only ;)
Magnetic Core Memory is facinating stuff to look at. How far we have come.
That is beautiful. Thanks for sharing, Dave!
The Apollo memory was rope memory, not core memory. It was in fact read only. You are correct, most core was did destructively read but the bits would be written back at low levels of logic on the board, not CPU level usually. There was enough local capacitance to assure the write back would complete. So - at a more macro level, this was not destructive in actual practice.
A driver circuit would rewrite the bit after it was read out.
Geoffrey Feldman Apollo used both read-only rope memory and read-write core memory. IIRC, there was about 9 times as much read-only rope memory (~72KB) versus read-write magnetic core memory (~8KB), but like most computers it required some actual read-write memory to store calculations and variable data and to maintain the stack as well as preserve register states during interrupt events and when switching between stored programs.
The Apollo computers did have core memory for RAM, as well as rope memory that functioned as ROM (where the programs were stored).
In about 1977 I had a summer job in Silicon Valley repairing older Data General minicomputers. We had 16k x 16 bit memory boards that were 15" square all core memory. It was great as you could turn the power off on the computer, restart it and your test program would still be in there. By that time however "semiconductor RAM" had completely taken over for new systems. We still shipped out used machines with core memory, however! It actually worked really well and was very reliable.
Now, at 74, I remember my time maintaining an RCA110 computer that had a 4K ferrite memory. This was around 1968. When it failed, I disassembled it and managed to find a broken ferrite ring on a parity bit. This particular systems 'word' was 23bit w/parity. What a challenge, what a memory!.. You are correct in that the data was destroyed when 'read' but the machines of the time always did a 'read/right' cycle to retrieve data, thus maintaining the memory. Now all you need is a spool or ten of some paper-tape programming.
I watched these being made at the Univac factory in late 1969. They were hand threaded by a bunch of ladies with very powerful magnifier lenses. Amazing stuff. Also, you have a sample of 2.5 D memory which is destructive, but a 3 D memory was also made that did not require the additional clock cycle to rewrite the bit.
I have a single Univac core memory plane. Tiny stuff. Quite amusing to compare to a Soviet era slice I have - the Soviet one has less total bits, but it's probably 4.5-5 times larger in physical size. And then to contrast it again, I have a bizarre Soviet core memory module out of a fighter jet of some kind - it's like a block construction, contains just insane numbers of hand-placed copper wires in a large 3-D structure, with massive amounts of square ferrite "cube" bits stacked in layers.. All developed within such a short timespan of each other. Fascinating stuff.
Incidentally my Univac memory slice has the Pentagon marking, a marking only used on machines delivered to the actual Pentagon.
*Edit:* Found the photo album I made of my collection: imgur.com/a/rvkUL
I had the honor of handling one of those old 3d core memory arrays, it was so cool, the ferrite cores were actually loose, they just floated/sat at the intersections of the wires, it rattled when you moved it.
Interesting seeing integrated circuits on the same board. I don't know the state of memory on monolithic silicon back in 1970 but it had to have been far more compact.
More compact maybe, but also much more delicate, much less proven, much more expensive, and for not much gain (it was quite slow compared to modern semiconductor memory, and also, core memory became faster and more compact as time went on). Core memory was produced well into the 80's, and reach pretty serious density levels.
I would love seeing you storing something on it. *Absolutely!*
Awesome to see this for real, I'd only ever seen drawn diagrams of these things. Had no idea what size the cores really were.
If it is from an ancient Siemens Mainframe I can get you in touch with a retired Technician...Ping me if you want contact Details
In the US Navy, I worked on a computer for the Trident C-4 Navigation system that used core memory. The thing I hated most about core memory was making sure the currents were adjusted properly because if they weren't you would get spurious data. You would think it would be a simple procedure but it's not, you had to get everything perfect.
Old memory is amazing. This is twistor memory. Telcos used piggyback twistor memories. Very cool. Thanks Dave, thanks to you first time I've seen the actual thing. I'll try to see if I can find datasheets on those controllers. I work for ST and joined when it was SGS-Thomson/MOSTEK
My dad was working for uncle scam back in the 50s in the bell labs and was working with some others in a group that first developed these ferrite core memory "webs" (as they called them back then). Awesome to see this one intact. Would be much more awesome if you can get it up and running for us to witness. Read some good ideas on how to do that from other comments. Wish my dad was alive to see this.
By studying the most basic ferrite memory core design, several dozens of computer nerds were able to figure out on how to create the 3 dimensional physical geometric pattern for the wires and for the ferrite cores using an over lapping technique using the basic CMOS principle for a proposed thin film transistor technology modified to act as a base for the original basic ferrite core memory which was started in 2011 and they were successful. Mass production on a micro scale was done successfully in the same year and they already have ironed out all of the kinks. What they have now in 2019 is a stockpile of thin film transistor based-ferrite core memory which is far easier to mass produce despite the fact it is more bulky, cumbersome, large size like a paper towel with a storage capacity of 2 terabytes. Being solid state, without having any moving parts to wear out, and it's flat ferrite core wafers can store memory data and information indefinitely without being affected by EMP, EMI, EMF, CME, Solar Flares, all data stored in them are safe from being damaged or destroyed.
I was looking for such a video for a long time. I was interested since Jeri Elssworth mentioned them!.
I have a small bare russian core memory array but didn't succeed in getting the writing/sensing right. I've always wanted to build a "core memory demonstrator" with just a micro, LCD and the memory, being able to put in some data like "hello world" and have that written into the cores. Wave a magnet across the core memory to see the data getting corrupted etc...
Streamtronics
I was thinking some kind of desk trinket along those lines. Something like a name plate or any little trinket with lighting and motion that corrupts the data would be awesome.
How about a clock that uses a magnet to reset the time every minute, and a MCU to refresh it?
Streamtronics You might find my kit interesting www.tindie.com/products/kilpelaj/core-memory-shield-for-arduino
Oh. Wow.
That's a thing that exists?
Huh...
That's a thing that exists. Neat.
Jussi Kilpeläinen
Oh. My. Goodness. That is freaking amazing. Thank you so much for designing such a thing!! I will be purchasing this in the future just to have something neat to play around with!
I will watch a video of you writing and reading from this. I find old tech like this fascinating
Please get some magnetic viewing film to show the magnetic fields.
I tried that, but either they aren't meganetised, or as a I suspect the field is just way too small to register.
That's disappointing :/ Thanks for the reply!
Wouldn't the magnetic flux be confined inside de toroid? It's a closed magnetic circuit, without any air gap.
They're toroids. The majority of the magnetic field stays in the ring.
This is So cool !
Thanks for sharing this man
I used to work on these machines back then - for Sperry Univac. Brings back memories working on systems so big you could have your tea break inside them! It's where I played my first computer game - Star Trek on a console printout.
When I first started working with computers it was on an IBM 360 mod 25, with one 16K module of core memory. The module was a 13 inch cube. This was in the late 1960s.
In about 1980 I was working in the studios of HTV Television in Cardiff, Wales (part of the ITV network). The studio lighting system had core memory systems to remember lighting conditions for different shows. We thought that they were pretty antique even then!
Those 70's electronics are just pur art!
In the late 60's I visited COGAR near Utica, NY. They had housewives weaving these core memory. Even the manager couldn't understand how they could stand it. Said they only worked about a half day, drank coffee and chatted all the time.
Back when I was in college (early '80s) I was given 2 old terminals. Sounded like a hurricane when you powered them up. When I tore them down, they had 2k of that ram in each. The keyboard was comprised of individual hall effect switches. If I hadn't parted them out, they could have flawlessly run continuously to date. Built like tanks to last forever.
I remember in my computer science class in '96 building a small array of core memory like this. Nothing so huge, probably only 64 bits at the most. It was a good project to bring the abstract thought of bits and bytes into reality while doing some communication out of the computer.
Back in 1980, I was a field service engineer. The computer running our machines was a DEC PDP 11-04. The thing I remember most about that computer was how hot it ran. The 8K core memory used a lot of current resulting in a lot of heat. I also remember that replacing a core memory board was VERY expensive. One of the common problems in those computers was the air filter behind the front panel. Most people didn't even know it was there. I'd pull the foam filter out and it was completely clogged with dirt.
I got a look at a ferrite core board when i was in Norwegian army in 1995, it was used in the mobile artilery as a targeting computer. According to the officer that had it on his shelf ( it was no longer in use by that time) it was hand made.
it would be fun to try to use it with a modern electronic build
As a kid in the 60's and 70's I remember looking at a picture of memory like this in the "World Book Encyclopedia". Funny... I had always had the conception that the ferrites were much bigger (due to the image in the encyclopedia). Very cool to see a real setup. Thanks Dave and thanks to the viewer who shared the memory with you. I wonder how long a set bit would persist in this memory. Maybe you could read what is in this piece.
Depending on the specifications, the expected retention period for ferrite core memory was anywhere from 10 to 100 years. Although, I think the chance is pretty high that you just erase everything when trying to read it, unless you do it just right the first time :P
I once saw an even tighter weave of ferrite core memory, I think it was from 1976. It's in the collection of the Institute for mathematical machines and data processing (vulgo "Informatics department") of Erlangen University. Last I saw it, it was on display in the blue tower, so check it out if you ever get to Erlangen in Germany.
I was 9 days old when this was made! Cool piece of tech.
How awesome!! I would love to see you power it up and write data to it!
Finally someone properly reads the word "data".
I love how youtube recommends me the good stuff :)
Soo, the german label says:
Core memory calibration:
400 Words, Date 1970-08-30, Name C413
The columns are labeled "lower limit", "average", "upper limit" for the LEFT and RIGHT bits.
no repairs made, only annotation a check mark ;)
This kind of makes sense with george s's comment "I took Dave's bit bucket challenge and counted 'em. Each of the 4 sections has 100 by 64 wires, or 100 64-bit words, equivalent to 800 bytes per section, 3200 bytes total ." because since there are 4 of them, 4 * 800 byte (400 words) = 3200 bytes.
Wunderbar
The first computer I ever operated was an Elliott 803. That ran on core memory too and the memory core was frickin HUGE.
They had an old magnetic core memory board on display when I visited the CERN computer centre.
There's something incredibly beautiful about that board; it's like looking at skillfully made neolithic stone axe.
wow one thing leads to another all the best from John in Texas
It wasn't elaborate machines that did it; it was all woven by hand.
I worked on old systems that had core memory in the early 80's and I also worked on systems with delay lines. Interesting fact about core memory, if you had an error in your program that caused a tight loop (like an instruction that branches to itself), you could actually burn out the core memory drivers. Also, with the delay lines, they came mounted as a long coil of wire in a case the size of a hardback book and if you hit the case it would corrupt the data.
My school required me to do an internship in a company of my choice. A friend of our family had a computer and tv repair shop and that's where i went. The guy gave me one of these. I was totally fascinated by the thing. I could ofc never expect to get it to work (i was 12 or 13). But just looking at it through a magnifying glass was awe instilling.
Geee... that's almost 30 years ago.
Interesting. I think I was in grade school in 1970 and didn't touch my first PC until I got my hands on a beast of an IBM PC sometime in the mid 1980's. It had two 5-1/4" floppy drives and an 8086 processor WITH a math coprocessor. Soon after we updated it and replaced one of the floppy drives with a monstrous 10Mb hard drive. DOS 2.0 had just arrived on the scene.
Yeah... AND 256k of RAM...
Siemens had a book out around that time with instructions on how to make those thingies by hand and how to troubleshoot the logic (Digitalspeicher mit Ferritkern, G.Keller, G. Pumpe & Rolf Kramer, 1971) . It proved invaluable to me when I build my first computer (1973).
There are nice videos on UA-cam showing how they make core-memories run! One even has original Apollo core-memory.
Looking forward to the video of using it.
In the 70's I repaired NSM juke boxes that used a very similar system to store the selections made, so being destructive on read meant the record only played once ideal
this modul is cut version , in the middle there is a space for more memory of core :D
From America With Love Thank you Brother and God bless you Sir
I believe that it was cheaper to have them manually wound by humans than create machines to make core memory, so chances are it was built by humans.
I worked as a senior toolroom technician at IBM Havant, UK in 1970. Part of my job was to maintain (and fix) the relay driven machines that welded the X and Y wires to the memory backplane. The first step was the cores were loaded into a fixture in the correct orientation by a vibrating machine and held there by vacuum, then they were manually inspected by a bloke with a high powered microscope - any fault at all and the whole thing was junked and later re-loaded with fresh cores.
After that, the loaded fixtures were carefully placed on the welding machine and vacuum applied again, then the operator fed all the X wires through by hand using a wide roller (not as easy as it sounds!), the correct tension was applied and they were welded and cut off all at once when he hit the weld button. The fixture was then rotated 90 degrees and the Y wires were done the same way.
Then they went for more microscope inspection and if OK went to Portugal where women fed the sense wires through by hand. On return to UK they were all manually inspected again before electronic tests.
Those relay driven machines were a bugger to fix, they were that old.
I have an old core memory board from an unknown computer, it is 4.5k bytes and I think is older than the one in this video as it has no IC's at all, all signals were routed around by diodes: I believe a similar one would have cost around US$36,000 in the 50's, dropping to around US$360 in early 70's after methods of mechanical assembly were perfected.
Knitted by Grandmas!
I started in computer programming in late 1974. The first system I worked on was an IBM System/3 Model 10 which had 24K of ferrite core memory. The OS took up 4K, leaving the other 20K for user programs. We were the odd birds since we programmed in COBOL rather than the native RPG II. You could write a pretty large COBOL program in that 20K as the linker broke it up into many overlays. Once I wrote a program so large it would not fit in memory. I finally hammered it in by replacing all of my carefully thought out, user friendly error message text with cryptic 3-digit codes.
Ah yes, also remember having to make the actual programs rarely exceed 16k. You leaned to write very tight code. Not like today, by any means. Finally along came 640k RAM and it was like a whole new world. All that ROOM !! LOL.... but then, no one writes in machine language anymore, either. I could write in Z80 and 6809 and 6502 code all day. (We don't need no stinkin' compilers...LOL) Was nice when "C" was invented.. Yes, alas, I really am old... {sigh}
Ingenious great clip
ICs and core-memory on one board... that's an important historical artefact!
This is something new to see
I'd love to see you get this running and try play around with it.
I have another board of core memory, roughly the same size (a little larger). It is marked as from a DGC Nova from 1972 but may have been used in a Danish computer. It has 16 K words of 16 bit so the cores are really small.
very cool, would love to see it working
That is not core rope. Core rope is a read-only system, famously used on Apollo, made by selectively passing wires though cores to select the data value, and the whole thing coiled up,
Exactly!
That's fascinating!
LOL @ Daves nerdgasm face when he realises what it is!
OMG do it Dave! Just a few bits like a date :)
UNBELIEVABLE.
I worked on a postal automation system that used an ITT computer with 32K X 32bit core memory in 1976 - 8. That computer was new then. I still have some cores somewhere, not from that computer, they made wonderful drive transformers for switch mode PSU's due to the square magnetic loop.
I worked on old 1960's era Navy Jets that were still in use in the early 1980's. They has the same magnetic ferrite core memory in the Nav-computers (80 lbs worth) about 16K memory...
Please note: on modern DRAM, we *still* destroy the data when reading (the tiny cell capacitor gets discharged). We don't notice, because the chip has a line buffer and writes back the data before reading another line.
There's probably still data stored on there - would be interesting to read it out to look for any plain text!
I could be mistaken but I thought the space shuttle used some of this memory as old technology is favoured for space flight. The z80 and 6809 were used in space probes until quite recently. All the bugs are known and the devices are more robust with larger structures.
Another reason they kept using the core memory for the Shuttle is that core memory is almost completely impervious to particle strikes and high radiation environments, where as semiconductors have to be radiation-hardened, which is expensive, and can affect the performance characteristics of the devices.
Dave, you could be the first person in the world to store porn on a magnetic core memory!!!!!! DONT MISS THE OPPORTUNITY!
Should a I store an ASCII dick'n'balls?
How about bitmaps.. each of those blocks seem to have 100*64 bits of data.. With 4 you could make animation :-)
Pretty sure he won't be the first. Pret-ty pret-ty sure.
Some ASCII art or a 100x100x4bits .jpg (seems to compress better at super low settings than GIF) could probably fit, though ascii art would probably look better
Nah, those Seimens guys probably already did it in 1970.
If you want to see some Core Store memory units, visit The National Museum of Computing in Bletchley, UK. You can also see machines running that use it and talk to experts about it!
You could flip certain bits there and have a look with the thermal camera...
You put Linux on what?
I'm going to have to stop playing the *Dave Jones drinking game* ...
It's too easy to get hammered, taking a shot every time Dave says, *Basically* ! 😮 🍺 😎
Reading data using the sense line also erased it if it was in the opposite polarity. The data was written back to one by counter intuitively writing to all but then inhibiting all but one during write.
to energise the ferrite core you could use the chips they use in the 8x8x8 led cube arduino projects. not sure on the reading part though. Fantastic find mate
Nice vid, I love the simplicity of core memory! I did a quick count, looks like (64*96)*4 = 24576 bits, or 3072 bytes, 3kB! Pretty miniscule! I'd love to try weaving some myself and making up something with an arduino to read/write to it.
Wow. Amazing video. Great item. Wow.
this is amazing!! The hard work they done for technology decades ago.
Back in my 1974 Digital Logic Class where we were using a DEC PDP8 in lab, my prof was showing us the core from one and explained that it cost several thousand dollars because it had to be made by hand. As he was handing it to the first student to pass it around, he horrified us all by clumsily dropping it. After a chuckle, he explained that the PDP8 had gone to semiconductor memory and that core was pretty much worthless at this point.
Interesting tidbit on magnetic core memory: Since it retained its values without power, if a program or the OS crashed, they would run a "core dump" routine to read out exactly what the computer was doing at the time of the crash. They could reconstruct what caused the crash. When I was studying computer science in the 80's, we would refer to a test where we had to write a lot of information down as a "core dump."
It is still called that, even long after computers no longer have core memory.
thumbs up for the bruce reference bruce.
Nice video Bruce
I knew a researcher who had a Dec PDP 8 in the antarctic. He said that They would power it down when they left for the winter and power it back up when they got back and the core memory was still at the same values. They didn't have to boot the computer, just toggle the run/pause switch. Awesome stuff even if it is bulky as anything.
There are some really good core memory training videos done by the army. Just search for "Electronics: Magnetic Cores I: Properties 1961 US Army Training Film"
Just as well we did not have to re-load the memory, we had to load it from paper teletype machine tape. took hours to load, had to load the boot louder program first, manually, bit by bit! Set up the instruction on a bank of 32 switches, then toggle the "load" switch, program counter automatically goes to next location, repeat with next instruction. We learnt to program like that, understanding what every bit did!
So you could get two of them and set them up to record on one as you read out the other right? Did they do that at some point? Sorry just found your channel and know very little about the subject
I wonder if there's anything still stored on it. Would be interesting to find out what it is.