IBM paperweight teardown: Reverse-engineering 1970s memory chips | Hacker News Reader

IBM paperweight teardown: Reverse-engineering 1970s memory chips

righto.com

104 pointspicture36 comments

Twenty years ago I bought two core memory planes (1960's, $6K new) for $50 each. Gave one to my dad, kept the other. Astonished these hadn't inflated like art work.

For the same reason technology from the early 1900s has little artistic value... most people don’t appreciate it. Having said that, I have a nice 1960s pay phone on display and a LC Smith typewriter from the 1920s also on display.

My children don’t even know what they are.

Probably because core memory was so ubiquitous in the 1960s and early 1970s, so there's a lot of supply. Almost every computer used core memory and each memory module had a stack of planes. IBM was producing literally billions of ferrite cores per year. (Of course that's not as impressive now when a gigabyte costs a few dollars.)

I wonder how many of these survived though?

I wonder if there could be a somewhere like cuba - sort of a lost kindgom of 50's cars.

There are a fair number of core memory planes floating around, both on eBay and with people I know. They were compact and made nice souvenirs when computers were scrapped, so a lot of people held onto them. As far as "lost kingdom", I've seen a bunch of core planes from Russia recently; they probably kept them in service longer.

Core memory is a beautiful thing. Here's a four kilobit (64x64) plane I bought some years ago:

https://geary.smugmug.com/Computers/History/i-jb2rgF5/A

Click the image to zoom in and see the detail of these (I think hand-woven) cores.

If you can get someone to say it's art then it's art.

I have seen a piece of fibre optic cable cut in half proudly displayed in an art gallery (fairly prominently even). Ultimately the people who appraise this kind of stuff have no idea what it actually does or how it works, if you want to be accepted you have to speak the right shibboleths.

There are some artists that have an extremely good handle on what computers mean for the world, but I'm not aware of many that would fawn over a die shot like we would probably do.

https://assets.moma.org/documents/moma_catalogue_2101_300062...

Unsurprisingly it was funded by Intel.

To be fair, art work typically doesn't inflate much either. Unless you're very successful, it deflates almost instantly as soon as the exhibition is over.

I once had somebody break into my cellar and steal an installation I'd built (a whole ton of handmade motors) for the scrap value.

Author here: anyone else have interesting IBM artifacts to discuss?

Those old IBM line printers... how were they so fast and (relatively) accurate? And why is my home printer so much slower?

For example, the IBM 1403[0] Model 3 could supposedly do 1400 lines per minute(!) Even if I assume 100 lines per page, that's still 14 pages per minute. My home printer is lucky to do five.

[0]: https://en.wikipedia.org/wiki/IBM_1403

$$$$$$$$$

Also the wikipedia link you pasted itself has a section on technology, and specifically how it was so much faster (pushed the paper into the ink rather than the ink into the paper).

I've done a lot with the classic IBM 1403 line printer. The basic idea is that a rotating chain has the characters on it and zips around at 90.3 inches per second. The printer has 132 hammers, one for each column on the page. When the right character lines up with a hammer, the hammer fires, printing the character. This lets the printer output a full line in 80 milliseconds.

The details of the print chain process are much more complex than you'd expect (so feel free to skip this paragraph). The computer has to constantly check to see when a hammer should fire. One important thing is that only one hammer lines up with a character at a time. (It's physically impossible to fire all the hammers at once.) During this time, the computer reads the corresponding character from memory and fires the hammer if it matches. To make this work, the chain/hammer timing has to match the core memory cycle timing. The chain spacing is very slightly different from the hammer spacing, so you end up with a vernier effect where the aligned character position changes much faster than the chain actually moves. I made an animation that might make things clearer: http://righto.com/ibm1401/printchain.html

Another thing that makes the printer fast is it has a hydraulic motor to advance the paper very quickly. Inconveniently, the printer at the Computer History Museum is leaking hydraulic fluid, so we need to mop it up regularly. (That's one advantage of your home printer.)

The print quality of the 1403 line printer was much better than competitors because it used a chain instead of typebars or a drum. In particular, if the timing was a bit off, the chain caused the character to be shifted left or right. Other approaches caused the character to be shifted up or down. A left-right shift is barely noticeable, while an up-down shift makes the text look wavy and awful.

By the way, a laser printer (e.g. Brother) is a good choice for a home printer if you want more speed and don't like the expense of ink.

That animation is very, very informative. Thank you for your blogs and stuff like this!

I love the breadth of knowledge on this site.

Thank you for this in depth explanation.

It's not that hard to find a fast printer if print speed is important to you. I have a Brother MFCJ6535DW inkjet printer that's rated at 35 ppm black and white and 22 ppm color. I haven't measured it precisely, but it's doing at least 20 pages per minute.

I think when it was new it cost around $500, but I got this one as a refurb for $180.

(my wife works in a state regulated industry and prints a lot of paper - 500 - 1500 pages/month, so the printer gets a workout, and consumables are cheap - a 3000 page black ink cartridge costs around $25, about half the price as toner for our old laser printer and has no other consumables to replace like a fuser drum)

Here's a fun IBM line printing video I've discovered thanks to your mention of those:

    The IBM 1401 mainframe runs "Edith"

https://www.youtube.com/watch?v=LtlrITxB5qg

I share your amazement. The thing was - they did everything mechanically. They were like chainsaws with accurate solenoids, in small soundproof booths.

Thanks for your work Ken. I am learning so much from you.

I have a 2" square cube of the original IBM Armonk (now "North Castle") hideous orange carpet. They had to replace all of it after the fire in 1995 and offered anyone who had an office these cubes.

Also an original IBM "Think" pad, though the leather is degrading (I grabbed it circa 1994 as Myers Corners was shutting down, really regret not just grabbing an entire box of them).

@kenshirriff has an IBM "Technology Sample Kit" circa 1986 that looks pretty interesting:

https://twitter.com/kenshirriff/status/1346517181098409985

That's me! kens == @kenshirriff

The technology sample kit was discussed on HN last week: https://news.ycombinator.com/item?id=25893087

Awesome! Love your Twitter feed!

Like how @dang is Dan G., @kens is Ken S. ;)

I have a solar powered IBM calculator, the size of a credit card. Got it from an on-site IBM CE at the insurance company data center I worked at.

All the vintage mainframe stuff is pretty mind blowing.

There is an awesome hidden gem on YouTube: CPU Galaxy. He has a huge collection of vintage CPUs.

IBM 9121 Mainframe CPU https://www.youtube.com/watch?v=s7lVfOi7su4

Dave from EEVBlog also made a video about it https://www.youtube.com/watch?v=xQ3oJlt4GrI

No sadly but i love watching you guys on CuriousMarc!

Dissecting the past brings context and clarity to the present: What a wonderful gift. Your Alto reverse-engineering in particular was masterful wizardry. Thanks for everything you do!

>"The Model 145 is notable as IBM's first computer that used semiconductor main memory. The computer is very large by modern standards, filling the blue cabinets below. One cabinet holds the CPU while another holds 256 kilobytes of memory chips. This computer predates the microprocessor, so the CPU is built gate-by-gate from many boards of integrated circuits. The Model 145 weighed over a ton, cost $5 to 10 million (in current dollars), and was roughly as fast as an IBM PC (1981)."

These old school chips were amazing. I recently watched this old mainframe chip disassmbly:

https://youtu.be/xQ3oJlt4GrI

Surprisingly clear circuitry, and a nice looking paper weight too. IBM and made in France! I guess they made some chips in France.

I hope that you would restore the paperweight. I was so intrigued that I looked for it on ebay with no luck.

What do you mean by restore?

Weren't the chips removed from the paper weight?

No, I looked at the chips under the microscope while they were still inside the paperweight. It wasn't easy but it worked.

Good happy to hear that.

It is very nice looking. You should frame it as an object somehow and add your analysis on the back of the frame. it would be worth a lot eventually in my opinion because your analysis identifies the components.

FYI your link to "Design of Monolithic Circuit Chips" is broken.

Thanks, I've fixed the link: http://doi.org/10.1147/rd.105.0370 (paywalled unfortunately)

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