Ken Shirriff
@righto.com
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Alto. Ex-Google, Sun, Msft. So-called boffin.
MiniZinc solver page: www.minizinc.org
Link to Pips: www.nytimes.com/games/pips
The article on HN that inspired me to investigate constraint solvers: buttondown.com/hillelwayne/...
Link to Pips: www.nytimes.com/games/pips
The article on HN that inspired me to investigate constraint solvers: buttondown.com/hillelwayne/...
Play Pips, our new dominoes game for all skill levels.
Every domino has a spot. Can you find where each belongs?
www.nytimes.com
October 18, 2025 at 4:20 PM
MiniZinc solver page: www.minizinc.org
Link to Pips: www.nytimes.com/games/pips
The article on HN that inspired me to investigate constraint solvers: buttondown.com/hillelwayne/...
Link to Pips: www.nytimes.com/games/pips
The article on HN that inspired me to investigate constraint solvers: buttondown.com/hillelwayne/...
If you're a programmer, I recommend looking at constraint solvers. This different paradigm will broaden your horizons. It's also much easier than I expected. See my blog for details: www.righto.com/2025/10/solv...
Solving the NYTimes Pips puzzle with a constraint solver
The New York Times recently introduced a new daily puzzle called Pips . The idea is to place a set of dominoes on a grid, satisfying variou...
www.righto.com
October 18, 2025 at 4:20 PM
If you're a programmer, I recommend looking at constraint solvers. This different paradigm will broaden your horizons. It's also much easier than I expected. See my blog for details: www.righto.com/2025/10/solv...
MiniZinc gave me a solution to the Pips puzzle in 100 milliseconds. Admittedly, this puzzle is rated "easy", but MiniZinc quickly solves hard puzzles too. Internally, MiniZinc uses complicated algorithms such as backjumping and constraint propagation, but I don't need to worry about that.
October 18, 2025 at 4:20 PM
MiniZinc gave me a solution to the Pips puzzle in 100 milliseconds. Admittedly, this puzzle is rated "easy", but MiniZinc quickly solves hard puzzles too. Internally, MiniZinc uses complicated algorithms such as backjumping and constraint propagation, but I don't need to worry about that.
I used a constraint solver called MiniZinc. I wrote constraints for the problem: the conditions on the grid, the shape of the grid, and the values of the dominoes. A few more constraints defined how the problem works. I didn't need to write algorithms because MiniZinc solves automatically.
![Code:
constraint pips[1,1] + pips[2,1] == 8;
constraint pips[2,3] < 5;
constraint all_equal([pips[3,1], pips[3,2], pips[3,3]]);](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:svh6dgjnpkdl4dhxahj4xvkv/bafkreidkdyzpspryzvkwiacmfwmdywyyi6tdvyuris2rcohcc3ippainke@jpeg)
![Code:
grid = [|
1,1,0|
1,1,1|
1,1,1|];](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:svh6dgjnpkdl4dhxahj4xvkv/bafkreids7pl26yehzdsfkmavx74xxoc7hl2hnj6hwdt452hlyss467qiy4@jpeg)
![Code:
spots = [|5,1| 1,4| 4,2| 1,3|];](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:svh6dgjnpkdl4dhxahj4xvkv/bafkreibmqg5qucjsi6su3g55hyaqh6u5cvsmjetfmb3hxktz2x5f3evu5m@jpeg)
October 18, 2025 at 4:20 PM
I used a constraint solver called MiniZinc. I wrote constraints for the problem: the conditions on the grid, the shape of the grid, and the values of the dominoes. A few more constraints defined how the problem works. I didn't need to write algorithms because MiniZinc solves automatically.
If you want to know more about the IBM 1403 printer, I wrote about how we played music on it:
www.righto.com/2019/09/risk...
I also made an animation to explain the extraordinarily complicated timing between the hammers and the chain to print characters: static.righto.com/ibm1401/prin...
www.righto.com/2019/09/risk...
I also made an animation to explain the extraordinarily complicated timing between the hammers and the chain to print characters: static.righto.com/ibm1401/prin...
Risky line printer music on a vintage IBM mainframe
At the Computer History Museum , we recently obtained card decks for a 50-year-old computer music program. Back then, most computers didn't...
www.righto.com
October 2, 2025 at 9:54 PM
If you want to know more about the IBM 1403 printer, I wrote about how we played music on it:
www.righto.com/2019/09/risk...
I also made an animation to explain the extraordinarily complicated timing between the hammers and the chain to print characters: static.righto.com/ibm1401/prin...
www.righto.com/2019/09/risk...
I also made an animation to explain the extraordinarily complicated timing between the hammers and the chain to print characters: static.righto.com/ibm1401/prin...
The hammers looked okay, but @tubetime.bsky.social found that hammer #83 was sticky. He cleaned it and then the printer worked, just in time for the demo. (Stop by the museum on Wednesdays or Saturdays to see the system in operation.) Photo shows a hammer from an earlier repair.
October 2, 2025 at 9:54 PM
The hammers looked okay, but @tubetime.bsky.social found that hammer #83 was sticky. He cleaned it and then the printer worked, just in time for the demo. (Stop by the museum on Wednesdays or Saturdays to see the system in operation.) Photo shows a hammer from an earlier repair.
We took the hammer unit out of the printer. Fortunately, IBM designed the printer for (relatively) easy maintenance. Inside the printer are two rails that can be attached to the back. The hammer unit slides out and tilts for access. You can see some hammers and coils; more are underneath.
October 2, 2025 at 9:54 PM
We took the hammer unit out of the printer. Fortunately, IBM designed the printer for (relatively) easy maintenance. Inside the printer are two rails that can be attached to the back. The hammer unit slides out and tilts for access. You can see some hammers and coils; more are underneath.
The line printer uses a chain with raised characters that spins at high speed. It has 132 hammers, one for each column. When the right character on the chain is in front of a hammer, the hammer fires, printing that character. But if a hammer fails, that column doesn't print, as you can see. 2/N
October 2, 2025 at 9:54 PM
The line printer uses a chain with raised characters that spins at high speed. It has 132 hammers, one for each column. When the right character on the chain is in front of a hammer, the hammer fires, printing that character. But if a hammer fails, that column doesn't print, as you can see. 2/N
The regular repeating features are probably blocks of cache RAM.
September 24, 2025 at 12:16 AM
The regular repeating features are probably blocks of cache RAM.
Marilou Schultz's rug is on display at SITE Santa Fe's current exhibition: "Once Within a Time"; let me know if you see it!
Photo credit: rug photo from First American Art Magazine (@firstamart.bsky.social).
Photo credit: rug photo from First American Art Magazine (@firstamart.bsky.social).
September 6, 2025 at 3:25 PM
Marilou Schultz's rug is on display at SITE Santa Fe's current exhibition: "Once Within a Time"; let me know if you see it!
Photo credit: rug photo from First American Art Magazine (@firstamart.bsky.social).
Photo credit: rug photo from First American Art Magazine (@firstamart.bsky.social).
If you want to learn more about Marilou Schultz's amazing Pentium Navajo weaving, see my earlier thread:
bsky.app/profile/righ...
bsky.app/profile/righ...
I recently saw an amazing Navajo rug at the National Gallery of Art. It looks abstract at first, but it is a detailed representation of the Intel Pentium processor. Called "Replica of a Chip", it was created in 1994 by Marilou Schultz, a Navajo/Diné weaver and math teacher. 1/n
September 6, 2025 at 3:25 PM
If you want to learn more about Marilou Schultz's amazing Pentium Navajo weaving, see my earlier thread:
bsky.app/profile/righ...
bsky.app/profile/righ...
To learn more about the 555 timer rug, see my latest post: www.righto.com/2025/09/mari...
A Navajo weaving of an integrated circuit: the 555 timer
The noted Diné (Navajo) weaver Marilou Schultz recently completed an intricate weaving composed of thick white lines on a black background, ...
www.righto.com
September 6, 2025 at 3:25 PM
To learn more about the 555 timer rug, see my latest post: www.righto.com/2025/09/mari...
Marilou Schultz first made a chip rug in 1994, when Intel commissioned a rug based on the Pentium as a gift to AISES (American Indian Science & Engineering Society). The Pentium weaving used natural dyes, while the 555 weaving uses aniline dyes and some metallic threads for more intense colors.
September 6, 2025 at 3:25 PM
Marilou Schultz first made a chip rug in 1994, when Intel commissioned a rug based on the Pentium as a gift to AISES (American Indian Science & Engineering Society). The Pentium weaving used natural dyes, while the 555 weaving uses aniline dyes and some metallic threads for more intense colors.
Marilou Schultz based the rug on a photo by Antoine Bercovici (Siliconinsider). He used a special dark field microscope that produces a black background, highlighting the metal wiring on top of the silicon. The rug (left) mostly matches the photo (right), but there are some artistic changes.
September 6, 2025 at 3:25 PM
Marilou Schultz based the rug on a photo by Antoine Bercovici (Siliconinsider). He used a special dark field microscope that produces a black background, highlighting the metal wiring on top of the silicon. The rug (left) mostly matches the photo (right), but there are some artistic changes.
Here's a photo of the silicon die of the 555 chip—it's packaged in a metal can, rather than usual plastic rectangle, with 8 pins in a circle. If you zoom way in, you can see the pattern on the silicon matches the rug, in particular, the three large squares with a 王 pattern.
September 6, 2025 at 3:25 PM
Here's a photo of the silicon die of the 555 chip—it's packaged in a metal can, rather than usual plastic rectangle, with 8 pins in a circle. If you zoom way in, you can see the pattern on the silicon matches the rug, in particular, the three large squares with a 王 pattern.
What do you mean? Let serves are a common thing.
August 31, 2025 at 2:24 PM
What do you mean? Let serves are a common thing.
Those are my photos :-) I wrote more about the Globus here:
www.righto.com/2023/01/insi...
www.righto.com/2023/01/insi...
Inside the Globus INK: a mechanical navigation computer for Soviet spaceflight
The Soviet space program used completely different controls and instruments from American spacecraft. One of the most interesting navigati...
www.righto.com
August 24, 2025 at 10:26 PM
Those are my photos :-) I wrote more about the Globus here:
www.righto.com/2023/01/insi...
www.righto.com/2023/01/insi...
Yeah, those are my photos :-)
I reverse engineered the Globus here: www.righto.com/2023/01/insi...
I reverse engineered the Globus here: www.righto.com/2023/01/insi...
Inside the Globus INK: a mechanical navigation computer for Soviet spaceflight
The Soviet space program used completely different controls and instruments from American spacecraft. One of the most interesting navigati...
www.righto.com
August 24, 2025 at 1:02 AM
Yeah, those are my photos :-)
I reverse engineered the Globus here: www.righto.com/2023/01/insi...
I reverse engineered the Globus here: www.righto.com/2023/01/insi...
The first chip is the Fairchild 9040 flip-flop, which was manufactured by Navajo workers at the Fairchild's facility in Shiprock, NM. The second chip is the famous 555 timer. The weaving is based on a photo by Antoine Bercovici (Siliconinsider) that I suggested to the artist.
August 18, 2025 at 6:56 PM
The first chip is the Fairchild 9040 flip-flop, which was manufactured by Navajo workers at the Fairchild's facility in Shiprock, NM. The second chip is the famous 555 timer. The weaving is based on a photo by Antoine Bercovici (Siliconinsider) that I suggested to the artist.