

Complete computer designed and built from logic gates - jgrahamc
http://www.homebrewcpu.com/overview.htm

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jacquesm
a repost of:

<http://news.ycombinator.com/item?id=741639>

By popular request...

What I find extremely impressive is that he not only designed a computer from
the ground up using nothing but TTL, he _also_ designed the cpu and
instruction set.

Most people would be tempted to re-create an existing design, this guy
basically did on his own what would have taken a whole corporation consisting
of lots of people 30 years ago.

It's not like a re-enactment, it is a completely original design.

~~~
cabalamat
Surely it's more fun to do your own design? It would be for me, anyway.

~~~
jacquesm
Definitely, but designing an instructionset is not that easy. Small changes in
how you lay out your instructions can have a big impact on the design.

The nicest I think are 68K and mips, everything else is pretty messy.

A good standard by which to measure how good an instruction set is is how many
lines of code it takes to simulate it.

~~~
RiderOfGiraffes
> _The nicest I think are 68K and mips,_

No, the nicest is the ARM.

~~~
jacquesm
ah, yes. Missed out on that one! I actually had one of the first ARM based
machines straight out of 'Acorn' (before they went on general sale) through a
deal with the dutch importer (lvl rocom).

The only software that it came with was a game called 'lander', it didn't do
much other than display this amazing 3D landscape that you could fly across to
shoot at stuff.

We'd be mesmerized for hours by how smooth the animation was.

It was pretty sad to see the ARM to go down the way it did only to be
resurrected as an embedded platform. What a missed chance!

Just about everything coming out of Acorn (except maybe the atom) was
engineered so well it was quite amazing.

The bbc micro had a dual processor option (in those days pretty much unheard
of, the only thing that would come close would be a float coprocessor in an
ibm, but that would not be a secondary general purpose processor) through a
flatcable connector on the bottom of the machine called 'the tube'. The ARM
was originally designed to be one of several coprocessors available for the
bbc.

I heard an interesting anecdote about the ARM at the time, that it was the
only processor designed that worked on first silicon. They'd built a simulator
for it and used that to verify the design.

I didn't get much assembly time on it though, this was just about when Acorn
went under as a manufacturer of general purpose computers (the 'master series'
bbc were also pretty good). So I moved on to the Atari ST and the IBM pc (a
homebrew machine that I built on top of a filing trolley, a buddy of mine
welded a steel sheet to an empty folder hanger trolley and that became the
basis for my pc, motherboard bolted on top, powersupply to the bottem. It
looked pretty scary :) ).

------
bmunro
>Shortly after I declared Magic-1 "hardware complete", I casually mentioned to
my wife that I was starting to think about Magic-2. Her response was swift,
and final:

> "No, there will be no Magic-2!"

...omitted...

> She's the love of my life, the woman I plan on growing old with, mother of
> my children, my partner and best friend. I have to respect her wishes on
> this.

> So, there will be no Magic-2.

> Instead, we'll call the follow-on project "Magic-16".

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joshu
This is awesome.

Surely there's some ROM in there. I can't imagine the microcode is in an FSM.

When I was at CMU, my capstone engineering class was to build a machine that
was capable of a small set of tasks (One that I remember was multiply two
16-bit numbers.) We were to optimize for some specific thing -- ours was "most
sleep" (that is, least work) and "least wire wrapping." So it was as simple as
possible; entire control path fit in a PLA for example.

Anyway, one of the other groups apparently optimized for AWESOME. We were
there with our single board and a multicolor cloud of wire-wrap; they showed
up with a multiple board computer. The boards had a pair of 68-pin IDC
connectors and two huge wide cables as a bus.

The machine basically was fully asynchronous and had no clock. One board was
an ALU, one was the control unit, etc. For their demo they both ran with one
or two ALU boards and got different performance.

This was 1995 or so, so quite progressive for the time.

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wallflower
Computers constructed from solely logic gates have an impeccable pedigree:
Apollo's onboard flight computer

"The Apollo flight computer was the first to use integrated circuits (ICs).
The Block I version used 4,100 ICs, each containing a single 3-input nor logic
gate. The later Block II version used dual 3-input nor gates in a flat-pack,
approximately 5,600 gates in all. "

<http://en.wikipedia.org/wiki/Apollo_Guidance_Computer>

~~~
lupin_sansei
Didn't the Apollo flight computer crash/have to be restarted during the
landing phase?

~~~
dan_the_welder
Yes.

~~~
Luc
No it didn't. It worked perfectly as designed. Buzz Aldrin left the rendezvous
radar on, which together with the data from the landing radar overloaded the
computer, but it handled it properly and kept on running. Great work, job well
done.

------
Luc
Nice. I've got a 4-bit one built from relais by a German guy:
<http://www.relaiscomputer.de/kurz6.htm>

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rlm
I wish I knew how to get started on something like that...

~~~
jgrahamc
You could start by building a ALU and work up from there.

~~~
rlm
I've built an ALU for a simulator ;)

But I wouldn't know where to go from there and I wouldn't know how to make a
physical one.

Are there any OCW-courses (or similar) on the subject? Preferably with a
hands-on approach :)

~~~
hc
[http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-
Compute...](http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-Computer-
Science/6-004Computation-StructuresFall2002/CourseHome/)

~~~
rlm
I looked around a bit and found out that the course from '07 includes video
lectures. :)

<http://6004.csail.mit.edu/Spring07/>

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kapuzineralex
Incredible! Both thumbs and both big toes up!

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smithjchris
Lovely project. Wish I had the patience for that (and a nice logic analyser).
By the time I'd started at university, it was all FPGAs, HDL and simulation. A
shame really.

The nearest I ever got was a pure TTL digital clock.

~~~
jacquesm
There is something very good about learning the hard way how to debug a logic
circuit instead of having an FPGA in some factory made board. You get to see
how finicky hardware really is.

------
asciilifeform
Undeniably impressive, but saddening nevertheless. The man insisted on
replicating the mistakes of the past: Von Neumann bottleneck, C, Unix. This
creation is a "model airplane" - a world-class one, to be sure, but a model
airplane still.

~~~
JeremyChase
Building the hardware is an amazing project. You are suggesting that he should
have designed a new architecture, core language, and operating system as well?

Maybe he should just cure cancer too.

