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Ed S
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Ed S
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Curiosities  - 
 
Ever upgraded a computer by stacking RAM chips? Or made a ROM switcher? Ever bought a product with pre-doubled RAM chips (if you bought a memory expansion for an early PC, you might have. TI even sold pre-stacked RAM chips.) Here are some piggybacked chips from around the web (see captions for links, details and credits.) The most extreme is a stack of 35 chips, to make a 35-bit wide word for a Lisp engine. In an Osborne, of course.
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As I recall, a stacked chip was one of the ways to do your own TRS-80 video RAM upgrade (from 7 bit to 8 bit) so that you could have lowercase letters.
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Ed S

Discussion  - 
 
"Thousands of sunflowers were planted by families, schools and community groups in honour of Turing as part of the study..." "The spirals in sunflower seed heads often conform to a Fibonacci number (0,1,1,2,3,5,8,13,21,34,55, and so on, where each number is the sum of the two numbers before it). Turing was one of a number of scientists who tried to explain ‘Fibonacci phyllotaxis’, but he died before the work was complete."

via the aperiodical
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Ed S
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Discussion  - 
 
The HP-16C "Computer Scientist" wielded by mathematician and computer scientist D H Lehmer in his 1982 talk about the history of prime sieving, from the Computer History Museum - because of a unique feature.
...
About 05:16 he takes out an HP-16C "Computer Scientist" calculator and says:
"The remainder on division has been badly treated by the design engineers of the last decade. Most machines one cannot obtain r directly from m and n. This spring Hewlett Packard brought out the first handheld calculator - the 16C - which delivers the
remainder on division. And I'll show you one of them!
Looks like any computer but it'll do something every other computer will not do."

Video of the talk at
https://archive.org/details/camvchm_00005#

Ref:
https://en.wikipedia.org/wiki/Derrick_Henry_Lehmer

Hat tip to +Maurici Carbo 
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Maurici Carbo (Double Struck Capital)'s profile photoEd S's profile photoMaurici Carbo (nummolt)'s profile photo
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+Ed S I never head before about Sedenions!. I see: 𝕊
https://en.wikipedia.org/wiki/Sedenion
Thanks!
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Ed S
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Discussion  - 
 
What did computers first mean to you? I've a hypothesis that there have been several identifiable generations, perhaps like this, which is more or less by decade:
- computers to get useful work done
- computers to learn about computers
- computers for games
- computers for writing and office work
- computers for education and investigation
- computers for entertainment
- computers for communication

However, even in the field of say communication, we've had BBS, IRC, email, Usenet, Forums, Social Media, realtime voice and video. In the field of entertainment, we've had tic-tac-toe, text adventures, video games, online multiplayer games, flash games, television (more or less), cinema (more or less), radio (more or less), books (more or less)
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Calculation/Programming
53%
Entertainment
29%
Work/Business
5%
Education
8%
Communication
5%
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One of my first exposures to computers was seeing one of mom's soap opera things and some chatroom thing and I'm like 'this thing can be used to talk to other people? Wow I'm living in the midle of dirtfarm nowhere so this might help the whole isolation issue.'

I was like... eight at the time.
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Ed S
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Portable Devices  - 
 
The Micromouse tournaments started in the 70s and reached Europe in 1980 (and on to the world at large) - and they are still going. See
http://cyberneticzoo.com/category/maze-ssolving-mmachines/
for a big maze solving computer from 1971 but I think micro mice are supposed to be self-contained. There's some history of the contest at http://davidbuckley.net/RS/mmouse/micromouse78.htm
and there are links there to developments in the 1980s.
...
There's an article on the original contest in the US at
https://web.archive.org/web/20070722204022/http://www.todaysengineer.org/2007/Jun/backscatter.asp

I was fascinated by the idea of these little micro processor controlled robots - I'm sure they appeared on British TV.

From the UK's New Scientist magazine:
"""A Swiss entrant, whose mouse was built with a watchmaker's precision, complained that the maze itself was not built precisely enough. As if to underline the point, a toy-car style entry from Lancaster University got bogged down attempting multi-point turns in narrow corridors.

Some mice bristled with sonars and photocells. But the home-built winner used two bits of bent-brass shim and half a dozen bare metal contacts to feel the maze walls. It worked almost perfectly, and like all good engineering it looked simpler than it was.

Two mice which failed to negotiate the maze nevertheless shared the prize in the Virtuoso Display section. Fred danced the Blue Danube Waltz to his own accompaniment; Midnight Sun from Finland wrote its name and then played a Beatles' tune while gyrating on the spot. Neither of these preprogrammed displays, of course, required an ounce of artificial intelligence.

Actually, entrants admitted that even a maze-solving program is not hard to write. "Anybody can write a maze-solving algorithm in a day," said Phil Yeardley, whose mouse was built from Lego bricks. The Lego mouse ran well until one of its feelers got stuck in a piece of sticky tape. "The biggest problem is steering," said one of the Finnish team, confirming that the mechanical problems are the toughest."""

Hat tip to +John Metcalf for posting about Apple II Robot Wars which reminded me of this alternative type of robot contest.
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"In 1981, Alan Dibley went so far as to saw off the keyboard of a Sinclair ZX80 computer and use it intact to control his Euromicro finalist, 'Thezeus'. Indeed, the 'Thezeus' series were largely built out of bits of junk-piano wire, rubber bands (for tires), and parts from radio-controlled models."

Some footage from '89 and '90 at
http://www.micromouseonline.com/2014/10/31/vintage-micromouse-video
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Tim Harford tells us this book is really good - see his take on short engaging talks at
http://timharford.com/2016/05/why-everyone-should-give-a-ted-talk-and-how-to-do-it/
(These skills are not just for TED speakers!)
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He's here by the way but rather snooty about who he talks to.
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Ed S

Shared publicly  - 
 
Don't try this at home. "Back in 2007, I was working for a radar company which had been slow to switch to LCD monitors. Being a radar shop, we had a few strong magnetron magnets lying around. One of these magnets was passed around among the engineers. Leaving the magnet under your monitor overnight would guarantee rainbows in the morning, and a shiny new LCD within a few days."
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I've just found some details about it, it was a Mitsubishi Megaview 37, in pictures it looks quite small, in real life it was immense!
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"It’s not just that McMurdo station is ugly—and it is lens-shatteringly ugly—but that there is so damned much of it. After sailing for three weeks with no signs of human activity, no power lines, no chemtrails, no evidence that we exist on the planet at all except for a mournful wooden cabin at Cape Adare, it’s jarring to see this open-air museum of prefabricated regret. Only the United States could find a way to create sprawl with a thousand people."
05.14.2016 · Shuffleboard At McMurdo. Somewhere below the Antarctic circle, I catch Tatiana, the waitress from the port side dining room, in a moment of leisure. This is the first time I've ever seen her off-duty. The galley crew on the Akademik Shokalskiy work twelve-hour days preparing, ...
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Expectation: _The Seeds of Doom_

Reality: decades old buried sausage squirts you in the face
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Ed S
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Computer Science  - 
 
Students can get pretty close to theoretical max performance - quite surprising to me.
 
Intel likes to advertise the theoretical gigaflops numbers of their CPUs, but how are they related to practice? It turns out that the answer is: very well!

One of the exercises in our course "Programming Parallel Computers" is, in essence, calculating the product AA^T for a 4000x4000 matrix A — see the exact problem statement below.

With a naive O(n^3) algorithm, taking into account that the result is symmetric, this requires 32 billion additions + 32 billion multiplications.

The classroom computers (Ivy Bridge, 4-core) that we use can do, in principle, 112 billion additions + 112 billion multiplications for 32-bit floats per second. However, this seems somewhat theoretical at first, as the numbers assume that:
– you use 8-wide SIMD vector operations for everything
– you use all 4 cores all the time
– operations are nicely interleaved and all cores have all the time new independent vector additions and independent vector multiplications available
– operands are already there in the registers (getting from L1 cache is already too slow),
– you get the maximum turbo clock frequency that the CPU can sustain for multithreaded code.

Anyhow, this means that for the naive matrix multiplication algorithm, 0.29s is the absolute minimum that you can get from these computers (without resorting to something like Strassen).

And how well are our students doing? This year we had at least 50 students (!) who are able to get below 0.6s, i.e., they are using at least half of the theoretical maximum gigaflops. And the best solution so far is 0.34s, which means that they are using approx. 85% of the maximum theoretical gigaflops of modern CPUs in practical applications!
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Well... Matrix matrix mult is a fairly unspectacular problem where it is actually possible to reach the peak. With some chances you can write the naive n^3 loop and icc will swap in an optimized library call automatically...
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Ed S
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Rebuild Projects  - 
 
The earliest surviving analog computer, from over 2000 years ago, lovingly recreated - by hand - in birch ply. Videos within show the mechanism in action. You too can predict the motions of the planets, the phases of the moon, and even eclipses, if you have two years to spare on a project like this.
Ref https://en.wikipedia.org/wiki/Antikythera_mechanism
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+Maurici Carbo
ah lego. Is there anything it can't do...
:-)
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Ed S
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Discussion  - 
 
The 2k ROM of the original and first ever calculator wristwatch from HP - dumped! New opcodes discovered. Quite an adventure. Lots of photos too. "Again after hesitating many weeks ... I finally connected 1.5 Volt power to the module and tried to measure some signals with the oscilloscope. This was very difficult, because I could damage easily one of the tiny bond wires while applying the probes. And after 10 Minutes of measuring exactly this happened. I was totally upset, because I never could reconnect any bond wire, and I saw my last chance gone to get to the ROM code." Fortunately, that wasn't so.
Ref: https://en.wikipedia.org/wiki/HP-01
There will be a replacement for the famous HP-01 chipset soon available. I will offer it as a repair kit in July for international shipping. All you have to do: remove the display from the defective circuit, attach it to the new circuit and insert the replacement into the case.
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Ed S
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Computer Science  - 
 
“Dynamic typing: The belief that you can’t explain to a computer why your code works, but you can keep track of it all in your head.” —@chris__martin
In my previous post, The Wisdom of Programming Quotes, I called out some quotes that look good on the surface, but turn out to promote the wrong ideas about software development. I have also posted…
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“Much of the essence of building a program is in fact the debugging of the specification.” — Fred Brooks

lol, we, Ada programmers, don't debug specifications - we debug software requirements xD [specification has specific meaning in case of Ada]
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