Still holding some secrets

The Antikythera Mechanism visits the Astronomy Picture of the Day once again.

Ring of fire eclipse

Still more reveals for the Antikythera Mechanism. A preprint suggests a zero point for the gizmo of 22 December 178 BCE.

Care for a game?

Betsy Golden Kellem reminds us that Elektro wasn't the only box of electronics and blinking lights on display at the 1939 New York World's Fair. There was also The Nimatron.

Win XP still ticking

Scientific researchers have many reasons for keeping aged computing hardware alive, as Anna Nowogrodzki reports: lack of funds to upgrade, stability and durability, and even—sometimes—performance.

For [neuroscientist Bjoern] Brembs, older PCs offer another crucial feature that was lost when Microsoft replaced its text-based operating system, MS-DOS, with Windows. MS-DOS “handles data as they come in with no buffering delays”, says Brembs, who exploits this feature for his fruit-fly flight simulator. “In Windows, so many things are constantly happening in the background,” Brembs says. You might want to take measurements at intervals of precisely 50 milliseconds, but the operating system might be able to manage only an average of 50 ms, with intervals ranging from 20 to 80 ms, depending on what else it has to do. “For flies,” says Brembs, “such massive delays are perceivable.”

Orrery

The Antikythera Mechanism was recently featured on Astronomy Picture of the Day.

Green and black

Rich Maddison of the RAF keeps his flight log on a Psion 5 -- and other vintage technologists, as reported by Michael Dempsey.

Dragon Hand

For the longreads shelf: Freeth et al., "A Model of the Cosmos in the ancient Greek Antikythera Mechanism." As summarized by Jennifer Ouellette and a report from University College London, researchers have figured out how the gearing on the face of the clockwork cosmos worked.

B200

A good skim of the history of selling computers via advertising, from Ryan Mungia.

... a striking Burroughs ad from 1964 shows a dramatically-lit photo of its B200 system with the headline, “angry young computer.” Beneath is a short bit of copy, which describes how the B200 can “outdo any computer in its class” and “gets angry” (just like a human!) when people purchase other machines “on the basis of name or initials.” Without mentioning IBM by name, the ad pokes fun at the industry leader while simultaneously touting its own brand in a witty way.

German and Connecticut

Ken Shirriff prints a visualization of the Mandelbrot fractal with an IBM 1401 and peripherals at the Computer History Museum.

The 1401 didn't need to be programmed in assembly language - it supports languages such as Fortran and COBOL - but I wanted the full 1401 experience. It does amaze me though that you can run a COBOL compiler on a machine with just 4,000 characters of memory.

Patch

Frank O'Brien explains, in exceptional detail, the hardware problem that vexed the Apollo 14 mission, and the dance of software fixes that kept the Moon landing on track. TIL about core rope memory.

777

At Living Computers: Museum + Labs, a DEC PDP-7 bootstrapping and running UNIX Version 0.

Special guest appearance by a strip of paper tape.

Versatile

The Antikythera Mechanism finds its way into the newest iPhone.

A Portable Cosmos

Solving the puzzles posed by a broken, corroded mechanical gizmo found by sponge divers in the waters off a small Greek island might seem, at first thought, unrelated to the problems of debugging a software service or improving the user experience of a new mobile app. But, as Alexander Jones in A Portable Cosmos (Oxford University Press, 2017) recounts the researches into what is now called the Antikythera Mechanism, discovered in 1900 as part of the cargo of a shipwreck, some surprising parallels with current software development practices come into view.

Ever since the bronze fragments of the Mechanism were brought to the surface, archeologists and other technologists have trained increasingly sophisticated tools on it, from detailed drawings, to progressively more detailed photographs, to (from 1988) radiological focal plane tomography (to look inside it, non-destructively), to reflectance transformation imaging (a super-contrast way of reading the inscriptions on the front and back of the device). This is reverse engineering on a millennial scale.

Our current understanding is that the Antikythera Mechanism was made in the first century BCE. About the size of a shoebox standing on end, it housed an intricate assemblage of gears, driven by a hand crank on the side of its enclosure. On what we call the front, a miniature solar system of Moon, Sun, Mercury, Venus, Mars, Jupiter, and Saturn revolved within two bezels marked with the constellations of the Zodiac and the months of the Egyptian calendar. On the back, pointers moving across two spiral dials (and three smaller dials) displayed celestial events in 19- and 76-year cycles. Bronze plates covering the front and back explained its operation and provided additional astronomical information.

So what does sussing out this—let me write it—analog dingus have to do with current technology practice? A few points:

Switching contexts to gain understanding: Or what I might call inference feedback loops. One of the back dials (one of the few that were completely preserved) is inscribed with the names of various athletic events that recur in four-year cycles, from the best-known Olympics to the rather obscure Naa and Halieia games. The Halieia festival took place in Rhodes; Rhodes was the home of the highly influential astronomer Hipparchus; and writings by Cicero refer to a celestial machine made there. Hence, it is likely that the Antikythera Mechanism was built in Rhodes (p. 94). Elsewhere, Jones accumulates information that points to the intended destination of the device: Epirus, in the far west of the Greek peninsula. Thus, we can connect the dots that a wrecked cargo ship traveling between these two points would be found someone between them—off the island of Aigila (also called Antikythera).

Similarly, Jones examines the orientation of the back dials and their pointers (p. 159). An arrangement that puts the pointers at the top pointing straight down and the pointers at the bottom parallel to one another corresponds to a zero point, or calendrical epoch, of 25 August 205 BCE. This date is not too far in the past for a device built in about 60 BCE.

The arithmetic of the gears: Some of the gears are sufficiently intact that we can count the number of teeth; others are just stuck together with 2000 years of gunk. But we can infer the missing gear trains. Since we know the patterns and cycles that each dial pointer would have had to trace, we can calculate the gear ratios necessary to produce the required movement. For instance, to account for a Moon pointer:

The pointer has to revolve 254 times clockwise around the dial in the same time as [main gear] b1 rotates 19 times; hence the desired ratio of periods is 19:254. A gear with 254 teeth would probably have been considered undesirably large... The prime factors of 254 are 2 and 127, so a gear with 127 teeth was unavoidable as the driving gear in an engaged pair. A gear with 19 or a small multiple of 19 will be necessary as a driven gear; since 19 is an uncomfortably small number of teeth for a gear, we can tentatively chose 38 as the smallest viable multiple. If we just had a gear pair with tooth counts 38 and 127, the resulting ratio would be four times what we want, so additional gears must be provided that collectively amount to a ratio of 1:4. (pp. 210-211)

Designed vs. actual use: For twelve decades, various purposes have been proposed for the whatsit. Early researchers reasoned that, since it was on a ship, it was an astrolabe or other navigational device. Later, as more details became available, it became clear that the machine could be used to predict eclipses and compute horoscopes. Jones argues, however, that while the mechanism could do these things, it was much better suited as a portable planetarium—a teaching device. And indeed, a student watching the planets in motion, with their anomalies and retrogrades, would have been much more engaged than the same student studying two-dimensional static diagrams—like the (very well done) diagrams in Jones's book. In today's world, consider the three-dimensional ball-and-stick model of biological molecules like DNA as compared to the same information rendered on paper.

Design for small spaces: The Saros dial on the back is divided into 233 cells. When a pointer points to particular cell, then the positions of Earth, Sun, and Moon are such that a lunar and/or eclipse is likely, and at a certain time. The Mechanism represents these facts with a combination of one-letter initials and two-letter ligatures: 8 characters to compactly represent, say, "Eclipse of the Moon, during hour 5 of the day; Eclipse of the Sun, during hour 12 of the day." An additional letter in the cell indexes to inscriptions on the back face of the machine, describing periodic starry events in greater detail. The index letter is a callout, in other words. (p. 152)

The Antikythera Mechanism is an altogether fascinating contraption, one that still keeps a few secrets to be revealed.

Gaming the benchmarks

What's holding us back from exascale computing? According to Katherine Bourzac's report, the simple answer is power.

See dee sea?

Bruce Sherry of Living Computers: Museum + Labs demonstrates a reconstructed Control Data Corporation 6000-series supercomputer.

Punch it

Charles Severance visits the Living Computers: Museum + Labs in Seattle.

Nifty fifty

Chuck House sends happy birthday wishes to the HP 2116 minicomputer, a 16-bit machine that preceded Digital Equipment's first 16-bit offering. The company offered it as an "instrumentation controller," lest it be seen as a competitor to hardware sold by the much bigger IBM.

Big Hex

Researchers at the University of Bristol have built an operational 16-bit computer the size of a climbing wall, in the service of teaching students processor architecture.

Preservation and presentation

Chris Garcia takes a walk through the 2016 Vintage Computer Festival.

Still won't take out the recyclables

Dag Spicer profiles Jim Sutherland's ECHO IV home computer, assembled in 1966 out of surplus modules from a Westinghouse Prodac-IV process control computer. The multi-cabinet machine was the forerunner of today's X10 ecosystem, but it also provided basic word processing, through a modified IBM Selectric typewriter.