Comments on: Processor built with Transistor-Transistor Logic

By: Art G. Granzeier III

Art G. Granzeier III — Fri, 03 Sep 2010 22:36:54 +0000

MCscrewdriver

Take a look at Prof. Douglas Jones’ Ultimate RISC (http://www.cs.uiowa.edu/~jones/arch/risc/). This computer has only one instruction – MOVE. Even with that limitation, this is actually a practical computer and can do pretty much whatever any other computer can do.

In his paper, Dr. Jones describes several commercial computers which came close to his Single Instruction Computer.

Search Google for SISC, Single Instruction Set computer or OISC for more about computers which had only one instruction.

Art

>kedavis, you are right :) I was just wondering >what is the absolute minimum number of bits, and >instructions for a system?
>
>Posted at 10:26 am on Nov 2nd, 2009 by >MCscrewdriver

By: Сергей

Сергей — Fri, 13 Nov 2009 18:42:21 +0000

I guess it would be funny to do the same thing with brains.

By: kedavis

kedavis — Wed, 04 Nov 2009 03:03:32 +0000

but it can’t DO anything. and why have a “return from interrupt” instruction in the middle of that nothing?

By: McScrewdriver

McScrewdriver — Wed, 04 Nov 2009 02:09:14 +0000

Kedavis, look at this gem: http://en.wikipedia.org/wiki/7400_series. Scroll down to History section and look at this image: http://en.wikipedia.org/wiki/File:YUNTEN.gif. Four bits, 6 instructions. Makes me happy every time I see it :)

By: kedavis

kedavis — Tue, 03 Nov 2009 02:46:51 +0000

Actually I learned on the 12-bit DEC PDP-8/L and I don’t think it had 56 separate instructions. But it didn’t have as many registers as the 4004 either.

Let’s see…

0, 1, 2, 3, 4, 5, and 6 were both basically instruction ‘groups’ with either a memory address or device code. Only group 7 was separate operations, and there weren’t very many of them.

Seems to me that having 56 instruction like the 4004 would have been a step UP… Then again the PDP-8 existed since the early 1960s, or even earlier if you include the predecessor PDP-5.

By: kedavis

kedavis — Mon, 02 Nov 2009 18:27:57 +0000

I’d say the Intel 4004 provides the best example for that. Most people don’t even know the 4004 ever existed, but most people these days probably don’t know about the 8008 or 8080 either, maybe not even the Z80 at this point. 4-bit architecture gives the flexibility to deal with 8-bit bytes somewhat easily and to use some bits to indicate that an instruction is longer than just one “word” or byte without using up the whole thing.

http://en.wikipedia.org/wiki/Intel_4004

Interesting reading!

By: MCscrewdriver

MCscrewdriver — Mon, 02 Nov 2009 17:26:20 +0000

kedavis, you are right :) I was just wondering what is the absolute minimum number of bits, and instructions for a system?

By: kedavis

kedavis — Mon, 02 Nov 2009 04:26:03 +0000

how do you get 5 instructions into 2 bits with only 4 possible values?

By: McScrewdriver

McScrewdriver — Mon, 02 Nov 2009 03:11:43 +0000

Congratulations. The next step is logical, RTL logic in a 2 bit system, with 5 instructions.

By: kedavis

kedavis — Sun, 01 Nov 2009 03:40:10 +0000

http://www.cca.org/tech/rcs/pdp12.html

I owned a few of these in the past, that’s where you can really get some appreciation for wire-wrapping and detailed logic. And core memory!

Among other features were the front panel with a separate light for EVERYTHING (not like the PDP-8/e which used a single row of indicators and a rotary selector so you could only see one “batch” at a time) and fully variable speed from one instruction per minute or whatever up to full, and with LINC mode it could boot from a magnetic tape with a single command from the front panel.

The CRT tube (worked like an oscilliscope, all text characters had to be “Drawn”) could be used as a “terminal display” with only the keyboard of the usual printing terminal (teletype) used for input, saves a lot of paper that way!

Being a “lab” machine it had A/D and D/A connections plus binding posts to six SPDT relays
which also each had their own indicator lights on the panel!

Great old systems, wish I still had one just to show the fancy-pants kids…

By: PocketBrain

PocketBrain — Sat, 31 Oct 2009 19:07:48 +0000

Welcome to 1968!

Good way to show you understand better than most how a CPU works. Gate-level logic construction; a lost art.

By: rrowell

rrowell — Sat, 31 Oct 2009 06:19:35 +0000

If you have never wire-wrapped a logic system with only old-school logic chips then you just would not understand. These days all the jaded kids say “FPGAs are cheap and easy” and you are right, I agree life is good :-) However, wire wrap was a beautiful thing, there is a reason NASA used in on the space shuttle. Kudos sir, an exquisitely ancient hack to remind of us an era bygone.

By: tj

tj — Sat, 31 Oct 2009 03:26:24 +0000

Very nice! I’ve also seen some nice analog circuits that did this same thing. You usually see them along with old S100 bus docs.

By: medix

medix — Sat, 31 Oct 2009 00:37:33 +0000

1337

By: Skyler

Skyler — Sat, 31 Oct 2009 00:26:19 +0000

@xrazorwirex:

College-level Digital Circuits is awesome. :)

I’m a lab assistant for that class(among others) and I have to say it’s one of my favorites. The things you can do with basic logic chips never ceases to fascinate me.

This makes me want to do something similar… I’m going to dig out my Digital textbook and see what I can come up with. :P