
Homebrew Cray-1A - rfreytag
http://www.chrisfenton.com/homebrew-cray-1a/
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jaysonelliot
When I was little, my grandfather worked at NSA in Fort Meade, Maryland. One
of my earliest memories is of him taking me, age five, in to see the Cray 1. I
remember crawling around on the bench, but of course, that memory could be
flawed. Who knows if they would have really let a five year old sit on the
fastest supercomputer in the world. Still, that's how I remember it, so I'll
stick with my memory.

It was the first computer I had ever seen, and it didn't disappoint. In 1976,
the idea of getting to see a computer at all was the ultimate marvel to a
little kid whose granddad had already started reading Asimov and Heinlein to
him at night. The Cray fit every imagination I had about what a computer
should be—sleek, huge, and like nothing I'd ever seen.

I don't remember anything else about the visit. I don't remember what else was
in the room, or what I thought all the people might be doing. All I remember
is that it was the first spark of fascination that led me to seek out any
chance I could get to be around any computer. Seeing that same machine
reproduced in miniature, right down to the bench, warms my heart. I wish my
grandfather were around to make it with me. I can't wait to give this a try.

~~~
julien_c
I read on the other thread the Cray-1 being caracterized as an important piece
of history.

What important computations were made on those machines, i.e., what did they
make possible? (Honest question)

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luu
_One of the coolest aspects of this machine is that everything is fully
pipelined. This machine was designed to be fast, so if you’re careful, you can
actually get one (or more) instruction every cycle. This has some interesting
implications – there’s no ‘divide’ instruction_

That's actually a common optimization, e.g, Itanium doesn't have divide; just
reciprocal.

I haven't spent time doing assembly optimization for a very long time, but it
used to be the case that, even in x86, you were often better off using various
tricks to avoid having to divide. I'd be interested in hearing if that's still
the case, from someone who does that sort of thing today.

 _The actual design was implemented in a Xilinx Spartan-3E 1600 development
board._

I love that hardware has gotten so cheap. When I was a teenager, I implemented
a Sega on an FPGA, and it took Virtex II board (very high end, at the time) to
handle everything. Now, an entire supercomputer fits on one of Xilinx's
Spartan (i.e., budget) boards.

~~~
microtherion
_That's actually a common optimization, e.g, Itanium doesn't have divide; just
reciprocal._

It's a bit more interesting than that: The Itanium doesn't have a reciprocal
either, just an _approximation_ of the reciprocal accurate to about 9 bits,
which can then be refined if more accuracy is needed.

~~~
mechagodzilla
That's the same way the Cray-1 does it. It uses 3 passes of newton's method
(and I think is accurate to 28 bits for the first time through).

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Palomides
btw, if you all haven't seen, he found a hard drive with an OS for this and
pulled the data, but needs someone to figure out the filesystem and stuff; you
can download the binary dump off his site.

<http://www.chrisfenton.com/cray-1-digital-archeology/>

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jamesmcn
I really hope this guy doesn't start a kickstarter for the hardware side of
the project. I would be completely unable to restrain myself from backing it.

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sciurus
Previous discussion: <http://news.ycombinator.com/item?id=1645291>

