The IBM 1401’s Unique Qui-Binary Arithmetic

November 5, 2015 by Brandon Dunson 12 Comments

Old mainframe computers are interesting, especially to those of us who weren’t around to see them in action. We sit with old-timers and listen to their stories of the good ol’ days. They tell us about loading paper tape or giving instructions one at a time with toggle switches and LED output indicators. We hang on every word because its interesting to know how we got to this point in the tech-timeline and we appreciate the patience and insanity it must have taken to soldier on through the “good ol’ days”.

[Ken Shirriff] is making those good ol’ days come alive with a series of articles relating to his work with hardware at the Computer History Museum. His latest installment is an article describing the strange implementation of the IBM 1401’s qui-binary arithmetic. Full disclosure: It has not been confirmed that [Ken] is an “old-timer” however his article doesn’t help the argument that he isn’t.

Ken describes in thorough detail how the IBM 1401 — which was first introduced in 1959 — takes a decimal number as an input and operates on it one BCD digit at a time. Before performing the instruction the BCD number is converted to qui-binary. Qui-binary is represented by 7 bits, 5 qui bits and 2 binary bits: 0000000. The qui portion represents the largest even number contained in the BCD value and the binary portion represents a 1 if the BCD value is odd or a 0 for even. For example if the BCD number is 9 then the Q8 bit and the B1 bit are set resulting in: 1000010.

The qui-binary representation makes for easy error checking since only one qui bit should be set and only one binary bit should be set. [Ken] goes on to explain more complex arithmetic and circuitry within the IBM 1401 in his post.

If you aren’t familiar with [Ken], we covered his reverse engineering of the Sinclair Scientific Calculator, his explanation of the TL431, and of course the core memory repair that is part of his Computer History Museum work.

Thanks for the tip [bobomb].

Tote Boards: The Impressive Engineering Of Horse Gambling

November 4, 2015 by Kristina Panos 21 Comments

Horse racing has been around since the time of the ancient Greeks. Often called the sport of kings, it was an early platform for making friendly wagers. Over time, private bets among friends gave way to bookmaking, and the odds of winning skewed in favor of a new concept called the “house”.

During the late 1860s, an entrepreneur in Paris named Joseph Oller invented a new form of betting he called pari-mutuel. In this method, bettors wager among themselves instead of against the house. Bets are pooled together and the winnings divided among the bettors. Pari-mutuel betting creates more organic odds than ones given by a profit-driven bookmaker.

Oller’s method caught on quite well. It brought fairness and transparency to betting, which made it even more attractive. It takes a lot of quick calculations to show real-time bet totals and changing odds, and human adding machines presented a bottleneck. In the early 1900s, a man named George Julius would change pari-mutuel technology forever by making an automatic vote-counting machine in his garage.

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Cutest Possible Atari Disk Drive

November 3, 2015 by Brian Benchoff 13 Comments

[rossumur]’s first computer was an Atari 400, and after riding a wave of nostalgia and forgetting the horrible keyboard found in the Atari 400, he decided it was time to miniaturize the venerable Atari 810 disk drive by putting an entire library of Atari games on a single microSD card.

SD cards have been slowly but surely replacing disk drives for just about every old computer system out there. You no longer need 400k disks for your old mac, and your Commodore 64 can run directly off an SD card. The Atari 8-bits have been somewhat forgotten in this movement towards modern solid state storage, and although a solution does exist, this implementation is a pretty pricey piece of hardware.

[rossumur]’s hardware for giving the Atari 8-bit computers an SD card slot is just one chip – an LPC1114 ARM Cortex M0. This, along with an SD card slot, 3.3V regulator, a LED and some caps allows the Atari to talk to SD card and hold the entire 8-bit Atari library on a piece of plastic the size of a fingernail.

Designing a circuit board doesn’t have the street cred it once did, and to give his project a little more pizzazz he chose to emulate the look of the very popular miniaturized Commodore 1541 disk drive with a tiny replica of the Atari 810 disk drive. This enclosure was printed at Shapeways, and with some enamel hobby paint, [rossumur] had a tiny, tiny 810 drive.

While this build does require the sacrifice of a somewhat rare and certainly old Atari SIO cable, it is by far the best solution yet seen for bringing a massive game library to the oft-forgotten Atari 8-bit home computers.

Thanks [lucas] for the tip.

No Pascal, Not A SNOBOL’s Chance. Go Forth!

November 3, 2015 by Rud Merriam 47 Comments

My article on Fortran, This is Not Your Father’s FORTRAN, brought back a lot of memories about the language. It also reminded me of other languages from my time at college and shortly thereafter, say pre-1978.

At that time there were the three original languages – FORTRAN, LISP, and COBOL. These originals are still used although none make the lists of popular languages. I never did any COBOL but did some work with Pascal, Forth, and SNOBOL which are from that era. Of those, SNOBOL quickly faded but the others are still around. SNOBOL was a text processing language that basically lost out to AWK, PERL, and regular expressions. Given how cryptic regular expressions are it’s amazing another language from that time, APL – A Programming Language, didn’t survive. APL was referred to as a ‘write only language’ because it was often easier to simply rewrite a piece of code than to debug it.

Another language deserving mention is Algol, if only because Pascal is a descendant, along with many modern languages. Algol was always more popular outside the US, probably because everyone there stuck with FORTRAN.

Back then certain books held iconic status, much like [McCracken’s] black FORTRAN IV. In the early 70s, mentioning [Nicolas Wirth] or the yellow book brought to mind Pascal. Similarly, [Griswold, (R. E.)] was SNOBOL and a green book. For some reason, [Griswold’s] two co-authors never were mentioned, unlike the later duo of [Kernighan] & [Ritchie] with their white “The C Programming Language”. Seeing that book years later on an Italian coworker’s bookshelf translated to Italian gave my mind a minor boggling. Join me for a walk down the memory lane that got our programming world to where it is today.

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[Quinn] Uses “Forsooth” To Win The Internet! –Also Fixes Apple IIc+ Beep

October 30, 2015 by Brandon Dunson 3 Comments

By this point we are all familiar with [Quinn Dunki] and her awesome engineering and retro hacking. [Quinn] aims her latest blog post at the Apple IIc Plus and its tone deaf bleeping beep. You can hear it for yourself in her beep comparison video after the break.

[Quinn] gets straight into the source code as expected and works through a logical process that she explains quite nicely while looking for the origin of the problem. There are some interesting and hard to follow moves in the source as control jumps around the ROM(s) all in the name of minimizing RAM. In proper form [Quinn] uses the ROM bank switching ability to her advantage as she see’s [the Woz’s] efficiency and raises him some fancy footwork of her own along with a beep that doesn’t make our skin crawl.

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If We Were All Astronomers There’d Be No More War

October 27, 2015 by Nava Whiteford 28 Comments

We recently reported on the amateur scientific work of Forrest Mims. Forrest is somewhat unique in being an amateur scientist who has consistently published his work in leading scientific journals. One area of scientific investigation has however attracted amateur scientific contributions of the highest quality almost since its inception, amateur astronomy.

You’ve likely heard of amateur astronomers like David Levy co-discoverer of the Comet Shoemaker–Levy 9 comet, and citizen science projects like galaxy zoo. But the history of amateur astronomy goes back far further than this, in fact as far back as 1781 William Herschel discovered the planet Uranus while employed as a Musician. Another entertainer of sorts, 1930s British comic actor, Will Hay, also made significant contributions discovering a “Great White Spot” on Saturn in-between films roles. Will was an avid amateur astronomer who regularly published his observations.

His belief that astronomy allows us to see humanity’s place in the universe in its true proportion led him to claim “If we were all astronomers there’d be no more war”.

While Will recorded his observations, hand drawn, in a log book. Modern astronomers digitally image the night sky. Digital cameras are of course optimized around the human visual system (as we recently discussed) making them less than ideal for astrophotography. Hackers have therefore made a number of innovations, one of the more audacious being the removal of the Bayer filter:

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This Is Not Your Father’s FORTRAN

October 26, 2015 by Rud Merriam 109 Comments

I learned to program FORTRAN IV in the spring of 1968 while working as an engineering technician in water resources. One of the engineers knew of my interest in computers and asked if I would like to learn FORTRAN. He needed to calculate the biological oxygen demand in streams but didn’t have any interest in programming. I jumped at the chance.

This was the days of big iron when the term computer meant a room full of heavily air-conditioned equipment. The State University of New York at Buffalo had an IBM 704 but they soon upgraded to a CDC 6400. To help pay for it they were inviting people to attend a seminar on FORTRAN so they could use the system. My job was with a small State of NY office and getting approval for me to attend was surprisingly easy.

Off I went for 6 weeks of training on one night a week. I still have my black “A Guide to Fortran IV Programming” by [Daniel McCracken]. For years, this was the FORTRAN bible, commonly referred to as just “McCracken”.

The programming went well and somewhere out there is a very old paper with a reference to the results it generated about the Chadakoin River flowing through Jamestown, NY.

This is FORTRAN’s strength – scientific calculations. It’s name says it: FORmula TRANslation.

Origins and FORTRAN IV

[John W. Backus] suggested to IBM a language to replace assembly language. Development began in 1953 for the IBM 704 and the project reached fruition in 1957. Not only was it the first general purpose high-level language, just beating out COBOL and LISP, but its compiler optimized the code since it needed to compete head-on with assembly language. It was the C compiler of its day in that regard.

That was not the only reason it attained success. Reducing the number of punched cards needed for a program by a factor of 20 over assembly helped considerably.

In those days, you needed to use a key punch to create a deck of punch cards. To be really good you had to know how to create a programming card that would let you skip through the fields on a FORTRAN card, or how to edit a card by duplicating it and holding one of the cards in place while you typed in new characters. Because of my fascination with computers I’d taken a key punching and automation machines class in high school so I was all set.

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