back to article Google chap reverse engineers Sinclair Scientific Calculator

A Google employee named Ken Shirriff has delved into computing history by reverse-engineering the code running Sinclair Radionics' 1974 scientific calculator. Shirriff's story of the calculator's genesis notes that in the early 1970s a scientific calculator was an expensive and extraordinary tool for which the likes of HP …

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Soldering exercise

I remember building mine - only way I could afford it!

I also remember having a transformer in a box with a small PCB and a reused earphone lead that plugged into an additional socket to power it from mains.

People used to laugh at the "almost accurate" answers (2/2*2 didn't come back as 2 from what I remember)

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Re: Soldering exercise

The QL had a 12 semitone octave . . .

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Anonymous Coward

Re: Soldering exercise

What's wrong with that. . How many would you have expected it to have?

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Re: Soldering exercise

I seem to remember that I got my self-build kit through a cheap offer in Electronics Today International. I was in my first year studying physics at Imperial College at the time, and everybody lusted after the HP calculators in the labs (solidly fixed in their cradles with security cables).

Of course the Sinclair shared RPN with the HP, but, besides lack of functions, suffered from lack of accuracy (only about three-and-a-half significant figures could be relied upon in practice). From what I recall, and involved some very convoluted exercises to do something as simple as produce the inverse of the number currently displayed. Of course, in a year or so, you could buy fully-fledged scientific calculators for pocket money.

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Childcatcher

Re: Soldering exercise

Yes, even the later ones - I had a Sinclair Cambridge Programmable - were pseudo-random number generators, accurate only to very few SF. They were slide rule replacements, but pretended they were more accurate than that.

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A bargain as a kit

It was fifty quid if you bought the ready-made one. But you could buy a kit and build it yourself for £16, which as an apprentice telephone engineer at the time was the same as my weekly gross wage. And extra geek points (before we'd even HEARD of geek points) for having built it yourself.

Funny thing about its use of RPN was that although it was hard to get used to, once you did it was very hard to get used to "normal" calculator operations. Rather like the way I now instinctively find myself using vi key-sequences whatever I'm editing in.

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Anonymous Coward

Re: A bargain as a kit

... like the way I now instinctively find myself using vi key-sequences whatever I'm editing in.

Yay! I'm not the only one :-D

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Happy

vi problem...

> Yay! I'm not the only one :-D

E492: Not an editor command: -D

:q!

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PJI
Happy

Re: A bargain as a kit

What, are there other editors with different instructions? Well, there is cat(1) if ed(1) / vi(1) are not available. No joke, I have had to create a config. file thus. It worked.

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Anonymous Coward

Re: A bargain as a kit

No, you're not the only one.

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Anonymous Coward

Re: A bargain as a kit

there is cat(1) if ed(1) / vi(1) are not available.

You missed the ultimate bare bones editor 'echo'.

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Re: A bargain as a kit

My *nix creds don't run that deep. But I can sympathize with 'edlin' and in some extreme cases - 'debug'

...sometimes the memories of creating a website via debug still wakes me up at night, but I did win the bet.

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As all Sinclair products, it was a pile of shite.

Yeah, you can find bigger piles of shite to compare it against and then it looks good, but it was a pile of fucking shite. An incredibly clever pile of fucking shite, but still a pile of fucking shite.

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Meh

Shutit-

Sir Sugar.

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Yeah obviously and Stephenson's Rocket was a POS too I mean top speed 15 mph the guy is having a laff, I don't even know why he is a selebrity

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@Brian de Ford

I commend your well-reasoned, insightful and thoroughly researched comment.

OR

Why did you bother?

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Pint

Despite all the downvotes, you are right - see the Black Watch (almost impossible to build yourself because of how tightly the components were squeezed in, and with a MTBF of about five minutes, you stood a 50-50 chance of exhausting the battery before it died forever), the calculators with nearly but not quite all the precision and speed of doing it via a slide rule, the much-loved but compared to an Apple ][, Atari 800 or BBC Micro really rather crap home micros, or projects like the MicroDrive or the washing machine on wheels...

.. but they are still loved. It's clearly not just Apple that has the fanbois, and Sinclair stuff was cheaper.

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Anonymous Coward

You do have to admire the sheer chutzpah of a guy who'll save money by digging up and using ICs that another company had decided were only useful as driveway fill.

Actually, now that I think about it, I wouldn't be too surprised if that's where all of these Atom CPUs have been coming from...

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One in front of me now.

There's one on the shelf in front of me now. Complete with it's cloth "bag". I can't pluck up the courage to put some batteries in and see if my soldering has survived the test of time.

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Paris Hilton

Re: One in front of me now.

I know that feeling. At the same time, though, if you cannot build up the courage now, will you ever? If it's left behind after you, would you prefer that someone with noob hands give a go at it, supervised only by your spiritual presence?

If it's meant to be just a display piece, no problem. But I can feel the niggling in your heart. Deep down in some deep corner of your psyche, eating away... no, screaming... at you every time you lay your eyes on its wondrously beautiful and tantalizing enclosure, even just out of the corner of your eyes, until one day you realize that while in those boring meetings you're doodling it, tracing its silhouette over and over again on your note pad. You start seeing it everywhere you look. It haunts your daily existence. The batteries... they're so close, and yet the distance you put between them is agonizing.

Dude... I know that feeling.

Paris, hooked on a feeling.

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long lost art of efficient programming

I enjoyed reading the paper, its nicely written, and it has a nice debugger if you're into that kind of thing.

Loved the part where it says "Calling NORMALIZE would have fixed this, but there wasn't space for the call" which just shows how tight everything was back then.

Today you'll be hard-pressed to find people that are adept at designing efficient algorithms of any kind.

"Install more memory" seems to be the mantra by which many designers live these days.

"Get a faster CPU" or "Get a bigger HD" also is exceedingly popular.

I miss the old days

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JDX
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Re: long lost art of efficient programming

Clever efficient programmers are all over the place still. But clever, efficient programming is a tool to use when needed rather than all the time - if your input requirements mean a simple O(N^2) solution is perfectly fine then why spend an extra two days writing a convoluted O(NlogN) one. They didn't do this for fun back in the old days, but because it was essential - nowadays we still do it when it's essential.

You don't rebuild your Ford Focus engine and tune it because it doesn't actually make your commute to work any quicker. But you do your track car.

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Re: long lost art of efficient programming

@JDX true but the mega-corps just rely on Moore's law to make their mega-inefficient code actually work. This is why knocking up a quick CV on your 2013 laptop looks and feels largely the same as knocking up a quick CV on your 1993 pc, just the code is 1000 bigger and 1000 slower but the hardware is also 1000 times faster.

If Windows 8 was written with the same level of dedication as that calculator, it would have enough power to go into orbit. Unfortunately is would also take 100 years ti write.

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Re: long lost art of efficient programming

I remember this application which was popular in the 80ies-90ies, "Norton Commander" or NC for short.

A kind of file explorer back in the DOS days based on a character GUI.

I remember everyone using it, but over time it grew and grew and got bloated until it didn't fit on a floppy any more.

Then someone walked in with something called "Volkov Commander" -VC for short

Now, this was a 100% rip-off from the original, except that it was written by some Ukrainian dude (if memory server), and in the Ukraine back in those days they didn't have the PCs we had here in the west, so that poor guy on his crappy machine decided to write his own version that worked on machines with low specs.

I have never forgotten, and each time something like this comes up i remember VC!

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Pint

Re: long lost art of efficient programming

I concur with all this. Back in those days programs weren't "written", they were crafted. Another example that springs to mind is ZX81 Chess (1K).

See http://users.ox.ac.uk/~uzdm0006/scans/1kchess/

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Pint

Re: long lost art of efficient programming

Anyone else remember the 'One Liners' programming contests of 30+ years ago? One line of BASIC being about 240 characters, varying slightly depending on which brand of affordable pre-PC home computer you had in the very late 1970s or early- to mid-1980s.

I wrote a cute little video game (one line!), and also a (text) adventure game *engine* (one line!, but needing an additional DATA statement for each dark and scary room).

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Anonymous Coward

When Sinclair was a genuis ....

ISTR the chip at the heart of one of his calculators was a power hungry beast that Texas Instruments insisted could not be run of a battery.

Sinclair devised a chopper circuit to power the chip only 10% of the time - thus allowing it to be powered by a battery.

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Still got mine

Mine's buried away in the loft but I do remember it working till the last drops of power in its PP3 battery died. Should try and dig it out. Probably worth, ooh, 99p now?

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Re: Still got mine

Wasn't the one with the PP3 battery the successor to this?

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Re: Still got mine

I'll give you 99p for it. Since I found out my still working MK14 would fetch £600 on ebay!

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Re: Still got mine

Didn't use a PP3, it took 4 AAA cells.

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MrT
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PP3...

... I had an old HP LED calculator - wedge shape, clicky buttons like an Oric 1 IIRC - that took 6xAAA, but worked just as well with a PP3 wired up across the first and last contact and fixed with black insulation tape on the top behind the screen. A bit cheaper to power than finding the right cells.

I later replaced it with the powerhouse that was the original Casio fx-82 ... and remember the cold flush of jealously when later beaten by fx-100 users on the "1++1=========(etc...)" race to 100.

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Looking at the page, and the linked calculator chip*

I would recommend this to any programmer or would be programmer as to what you can do with

old hardware and some motivation.

And the simulation engine shows you can do an IDE in the browser.

*(http://righto.com/ti)

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Haven;t got a sinclair but..

I did find whilst clearing my house out for a move an old Texas Instruments Ti 1250 calculator from c1976.

Put batts in switched on and the old red LED display lit up perfectly and the thing still works. a blast from the pasr.

Qwelak

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$400 for the competition??

I can't remember the exact year, but I remember that when I was in the market for my first scientific calculator (as a schoolkid), the competition was between the Sinclair and the Commodore SR-36 at about twice the price. I bought the Commodore (for a vaguely-remembered £59? ), and never regretted it. Everything worked perfectly right through to about 2005(*), during which time I never felt a need to buy another calculator. I think it was the keyboard which proclaimed "quality" just as the Sinclair one proclaimed "cheap, nasty".

The Commodore SR-36 was a real class act.

(*) except the rechargeable battery, whch I had to replace a couple of times (screwdriver and soldering iron required).

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Re: $400 for the competition??

I remember the Commodore calculator as well. Dad bought one for his building business.

Made in the UK at a factory at Egglescliff in the North East of England.

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Divide by zero

Pleased to see that the emulator has the divide by zero bug, although does not emulate it correctly. Divide by zero was possible on the Sinclair scientific resulting in the display of a count down or general numerical iteration. From memory this never stopped until you powered off, but the emulator seems to reach an input state after a short series of iterations.

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Still working, still quirky as they ever were

For a trip down memory lane see my pic of the scientific and standard calculators here:

http://www.flickr.com/photos/somersetman/4037850828/.

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Boffin

RPN is it? Let me break out my Forth compiler

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Coat

Roundworld's Bergholt Stuttley Johnson

Almost every Sinclair Product had a touch of genius but fatally flawed. If the design didn't have a flaw then it would be a failure due to poor production (Amstrad was horrified at the Production when he bought them).

Micro Smallest Radio (which wasn't even before it came out). TRF Reflex.

Grossly exaggerated specs of sub spec IC10 (Plessey) and IC12 (Texas)

Watch almost impossible to fit in case

Three iterations of pocket TVs with different flaws (oddly the first one the main flaw was too expensive, rare for Sinclair 2nd flaw battery. Last model was obsolete at release by LCD and Sony had better "flat" CRT to market first).

Wobbling RAM packs

QL "tape" cartridges

C5 bike using Washing machine motor.

We need people like Sinclair, but with better attention to Production Engineering and Quality.

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Re: Roundworld's Bergholt Stuttley Johnson

We need people like Sinclair, but with better attention to Production Engineering and Quality.

Probably, but without Sinclair leading the way a lot of such people would never have had the encouragement they needed.

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FAIL

QL "tape" cartridges

No names, no pack drill, but I heard this from the guy who was there...

"Make us a tape tester"

"OK"

"Er, it's failing too many"

"That's because they're failing"

"I know, let's just loop the test until they pass, or all the oxide wears off the tape..."

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My Dad bought me a non scientific calculator on HP!

I think it was in 1972 my Dad bought me a non scientific calculator on Hire Purchase from Dixons! Well it was £49.95!

IIRC it only did: add, subtract, multiply & divide.

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Well, I found the article interesting.

Back in the old days, I used to have to program everything to fit in 32K of memory (old DG RDOS). It was amazing what you could do if you had a modicom of knowledge about the processor and registers.

And yes, I did do RPN programming so the end user could enter their own formula (for oil well pressure analysis) and it would RPN it to act on the the data gathered. I was quite proud of that considering I wrote it back before we had spreadsheets.

Alan [No there are no links - it was way before we had any internet]

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Anonymous Coward

splendid work

Hats off to both the Sinclair bods who came up with the solution in the first place and to the chap who managed to reverse engineer the code, by just looking at the chip. Just when you thought you knew a thing or two, people like this give you a wake up call. Have beer on me.

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Wow. I thought the *hard* part was getting it to run for the length of time on 2 AAs

Basically by delivering short pulses at around 200Khz to the chip as (IIRC) this puppy is NMOS, not CMOS

I think that qualifies it for being the worlds first battery switched mode PSU in a consumer product (but I cannot swear to it).

I thought they just bought the chip and stuck in the board. I'd no idea the chip was even programmable.

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C5 motor

Wasn't from a washing machine, but from a torpedo motor manufacturer http://www.sinclairc5.com/facts/motor.htm

Just because the thing was assembled by Hoover, didn't mean they used the same components.

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Still got one, somewhere...

Helped me through my City&Guilds telecomm Full Tech. Cert. exam.

(Although my Grandfathers 'slip-stick' - slide rule - was what I used for the exams. More accurate, if my glasses were clean...)

Now, all I need is to find new batteries for my still-functional RPN Hewlett-Packard HP35 (Still with original leather pouch)

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Paris Hilton

I know that feeling. At the same time, though, if you cannot build up the courage now, will you ever? If it's left behind after you, would you prefer that someone with noob hands give a go at it, supervised only by your spiritual presence?

If it's meant to be just a display piece, no problem. But I can feel the niggling in your heart. Deep down in some deep corner of your psyche, eating away... no, screaming... at you every time you lay your eyes on its wondrously beautiful and tantalizing enclosure, even just out of the corner of your eyes, until one day you realize that while in those boring meetings you're doodling it, tracing its silhouette over and over again on your note pad. You start seeing it everywhere you look. It haunts your daily existence. The batteries... they're so close, and yet the distance you put between them is agonizing.

Dude... I know that feeling.

Paris, hooked on a feeling.

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