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Thanks for the explanation and clarifications.

If your logic is based on decimal digits and 2-input AND gates are very economical it works out very nicely. I didn't know what it was called or that it was in the 1401.

Another common representation that is easily decoded is what you get if you build a 5-bit-wide twisted ring counter. This is very widely used for decoded decimal counters (e.g. the CD4017 has this design internally), and Spehro even posted a circuit, a few years back in one of my threads, where the decoders are not even AND gates but are in fact the output LED's. Economically brilliant.

Tim.

What you have is sometimes called "base-1" arithmetic. I've only seen it used in simple examples for programming a Turing Machine. Maybe that's your calling ;)

-- Joe

-- Joe

Along similar minimalist lines:

^^^^^^ ^^^^^^^^^^

"Calling"? Maybe not. Check his arithmetic ;-)

...Jim Thompson

The ALU section of the 1401 was called "main star", and as you suggest probably did its math in star mode. Stuff outside was mostly BCD or character codes. The beast directly executed character strings out of core, so "assembly programming" was really machine code programming. You could type these programs directly into core via the Selectric.

I designed a SAR ADC, using transistors, and interfaced it to a 1401. I hasten to point out that the machine was already an antique when I did it. We hacked it in to the logic that was supposed to interface the realtime clock, which they didn't have. The 1401 RTC was actually a clockwork mechanism that drove switch contacts.

Geez, I've done a lot of weird stuff.

Here are a few tube counter things; 7M zip file. Some use the neon bulb thresholds as part of the decode logic.

ftp://66.117.156.8/Counters.zip

John

In article ,=20 snipped-for-privacy@highNOTlandTHIStechnologyPART.com says...>=20

For small values of "character string" and "assembly programming",=20 perhaps. Wasn't the Selectric well after the 1401?

The 1620 could add in whatever format floated your boat. It was=20 known as the "Cadet" because it Couldn't Add and Didn't Even Try. =20 Addition was done in a lookup table. ;-)

I know several who did similar things on 1130s. They were often=20 used for "instrumentation".

Those were binary machines, no? 16 bits, maybe.

I suppose google knows all this stuff.

John

ted

Yes, 1130s were binary. They were popular for that sort of=20 "project" though.

I recall that the 1130 was the first "personal" computer, and maybe the first computer that saw serious use in realtime process control.

IBM sure had a lot of very strange machines, up until the 360 line lent a bit of coherence. But IBM sort of lost interest in process control.

John

some

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of

2. > >> >> I hasten to point out that the machine was already an antique when =

ly

They didn't really lose interest as much as DEC cleaned their=20 clock, until the S/38 (and then 43XX) and then DEC lost their way. =20 IBM had the System-7 and Series-1, though they were a mess compared=20 to the DEC offerings. =20

--=20 Keith

DEC sure did "lose their way". Isn't it amazing how dominant companies can come crashing down so rapidly.

(Alan Kotok was one of my buddies at MIT... model railroad club ;-)

...Jim Thompson

Interesting read on the Analog Devices MACSYM system. We're still using a few...

I saw the demise of DEC coming a long way off. From a product perspective, the "Rainbow" was the nail in the coffin, IMO. I was not much impressed by our VAX-11/780, either. The examples of their arrogance and management incompetence is enough to fill a swamp but they couldn't manage that either.

How do you indicate the end of a number?

There is and there isn't. It is presumed covered in the combinatorial logic and sequential logic courses. But, of course it isn't really covered. Most state machine courses are trash as well.

ME: Use a transparent latch.

Xilinx Software: WARNING -- You are using a transparent latch!

John

by comparing with a ' Big number '

Got it.

any doubts here?

well, no, Unary stones.

The unary numeral system is the bijective base-1 numeral system. :-)

Don...

-- Don McKenzie

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