Booting from a vinyl record
So this nutty little experiment connects a PC, or an IBM PC to be exact, directly onto a record player through an amplifier. There is a small ROM boot loader that operates the built-in “cassette interface” of the PC (that was hardly ever used), invoked by the BIOS if all the other boot options fail, i.e. floppy disk and the hard drive. The turntable spins an analog recording of a small bootable read-only RAM drive, which is 64K in size. This contains a FreeDOS kernel, modified by me to cram it into the memory constraint, a micro variant of COMMAND.COM and a patched version of INTERLNK, that allows file transfer through a printer cable, modified to be runnable on FreeDOS. The bootloader reads the disk image from the audio recording through the cassette modem, loads it to memory and boots the system on it. Simple huh?
A handy diff argument handling feature that's actually very old
If only one of file1 and file2 is a directory, diff shall be applied to the non-directory file and the file contained in the directory file with a filename that is the same as the last component of the non-directory file.
'A Million Random Digits' Was a Number-Cruncher’s Bible. Now One Has Exposed Flaws in the Disorder.
A 1955 Rand Corp. book had a reputation as the go-to source for figures used by pollsters, analysts, researchers; engineer Gary Briggs has ruined it
I would say ruined is more than a bit strong, but good story.
Mr. Briggs hypothesized a technician dropped cards and put them back in the wrong order. He envisioned running computer simulations to re-create the error by moving a card or two out of place.
Non-POSIX file systems
Operating systems and file systems have traditionally been developed hand in hand. They impose mutual constraints on each other. Today we have two major leaders in file system semantics: Windows and POSIX. They are very close to each other when compared to the full set of possibilities. Interesting things happened before POSIX monopolized file system semantics.
Exploring mullender.c - A deep dive into the first IOCCC winner
I will discuss the code, how I got such old and obscure code to run, as well as include snippets from my conversations with one of the original authors (who was very helpful in figuring some of this out). If all that wasn’t enough I managed to obtain the original PDP and VAX source code, it will be hosted here with permission. I want to give a huge thank you to Sjoerd Mullender and Don Libes for their assistance and permission in reproducing some of this material.
A 35-year-old bug in patch found in efforts to restore 29 year old 2.11BSD
Larry Wall posted patch 1.3 to mod.sources on May 8, 1985. A number of versions followed over the years. It’s been a faithful alley for a long, long time. I’ve never had a problem with patch until I embarked on the 2.11BSD restoration project. In going over the logs very carefully, I’ve discovered a bug that bites this effort twice. It’s quite interesting to use 27 year old patches to find this bug while restoring a 29 year old OS...
Inside the 8086 processor, tiny charge pumps create a negative voltage
You might wonder how a charge pump can turn a positive voltage into a negative voltage. The trick is a “flying” capacitor, as shown below. On the left, the capacitor is charged to 5 volts. Now, disconnect the capacitor and connect the positive side to ground. The capacitor still has its 5-volt charge, so now the low side must be at -5 volts. By rapidly switching the capacitor between the two states, the charge pump produces a negative voltage.
When SimCity got serious: the story of Maxis Business Simulations and SimRefinery
SimCity wasn’t meant to be taken seriously.
The game was inspired by research on real-world urban planning concepts, and although it was created as a way for players to experiment running a city, the goal was to be fun rather than accurate. “I realized early on, because of chaos theory and a lot of other things,” said designer Will Wright, “that it’s kind of hopeless to approach simulations like that, as predictive endeavors. But we’ve kind of caricatured our systems. SimCity was always meant to be a caricature of the way a city works, not a realistic model of the way a city works.”
Die shrink: How Intel scaled down the 8086 processor
The revolutionary Intel 8086 microprocessor was introduced 42 years ago this month so I’ve been studying its die. I came across two 8086 dies with different sizes, which reveal details of how a die shrink works. The concept of a die shrink is that as technology improved, a manufacturer could shrink the silicon die, reducing costs and improving performance. But there’s more to it than simply scaling down the whole die. Although the internal circuitry can be directly scaled down, external-facing features can’t shrink as easily. For instance, the bonding pads need a minimum size so wires can be attached, and the power-distribution traces must be large enough for the current. The result is that Intel scaled the interior of the 8086 without change, but the circuitry and pads around the edge of the chip were redesigned.
Discovering Dennis Ritchie’s Lost Dissertation
It may come as some surprise to learn that until just this moment, despite Ritchie’s much-deserved computing fame, his dissertation—the intellectual and biographical fork-in-the-road separating an academic career in computer science from the one at Bell Labs leading to C and Unix—was lost. Lost? Yes, very much so in being both unpublished and absent from any public collection; not even an entry for it can be found in Harvard’s library catalog nor in dissertation databases.
Perhaps the highly anticipated moment that I’m going to contextualize today is totally inevitable, in a way. For years, there’s been a rumbling that Apple would take its knowledge of the ARM processor architecture and bring it to its desktop and laptop computers. Next week, at a virtual Worldwide Developers Conference, the iPhone giant is expected to do just that. Of course, many will focus on the failed partner, the jilted lover of the business relationship that led to Apple’s move to vertically integrate: Intel. But I’m interested in the demise of the platform Intel vanquished on its way to taking over Apple—and the parallels that have emerged between PowerPC and Intel over time. Today’s Tedium dives into Apple’s long list of jilted processor partners, leaning closely on the shift from PowerPC to Intel. Keep Apple happy, or else.
Extracting ROM constants from the 8087 math coprocessor's die
I opened up an 8087 chip and took photos with a microscope. The photo below shows the chip’s tiny silicon die. Around the edges of the chip, tiny bond wires connect the chip to the 40 external pins. The labels show the main functional blocks, based on my reverse engineering. By examining the chip closely, various constants can be read out of the chip’s ROM, numbers such as pi that the chip uses in its calculations.
Engineering and Technology History Wiki
The ETHW is not a “how-does-technology-work” site. The scope of the ETHW is historical; instead of focusing on the inner workings of technology, it aims to explain how the technology was developed, who were the major players involved, and what long term significance the technologies have. The ETHW is not only an encyclopedia of the history of technology, but it also contains a full range of materials that relate to the legacy of engineering, including personal accounts, documents, and multimedia objects. In that sense, it is a combination reference guide, blog, virtual archive, and on-line community.
A Codebreaker's Dream: The Bombe!
What is this, sporting dozens of colorful knobs, almost like a “turn-the-knob” toddler’s game at a playground in a nearest mall? This the awesome British Bombe electro-mechanical codebreaking machine which only had one purpose: to determine the rotor settings on the German cipher machine “ENIGMA” during WW2.
DVD+R and DVD-R; What was that about?
A format war within a format...
'Soviet Space Graphics' takes you inside the cosmic visions of the USSR
One new book transports readers back to the early days of Soviet spaceflight with an unbelievable collection of stunning, colorful and nostalgic images. “Soviet Space Graphics: Cosmic Visions from the USSR,” (Phaidon, 2020), released April 1, is a masterful compendium of images showcasing space design ideas from the then Soviet Union from the 1920s through the 1980s. It highlights the beauty of early space design in imaginative, colorful artworks.
The Early History of Usenet
>November 2019 is, as best I can recall, the 40th anniversary of the conception of Usenet. (What’s Usenet? The Wikipedia article is ok but not perfect.) I should have written a proper paper; instead, there will (probably) be an irregular series of blog posts.
I didn’t notice the series concluded a while back, so if you were waiting to read the whole thing, it’s done.
Touch And Go
Pondering the disastrous fate of the HP TouchPad, an early tablet based on WebOS that’s best known for being the subject of a well-remembered fire sale.
How are Unix pipes implemented?
This article is about how pipes are implemented the Unix kernel. I was a little disappointed that a recent article titled “How do Unix pipes work?” was not about the internals, and curious enough to go digging in some old sources to try to answer the question.