
Homebrew Cray-1A - davidbarker
https://www.chrisfenton.com/homebrew-cray-1a/
======
fentonc
This really has been posted here a lot - Well, for those following along at
home, this story actually got a relatively recent update - as of this spring,
the 1/10-scale Cray-1A is now residing next to its bigger self in the Computer
History Museum in Mountain View!

~~~
MrMorden
Did the FOIA requests include NSA? You’d want a copy of FOLKLORE if it’s
releasable; there’s at least one Cryptolog article about it that’s been
declassified.

[https://www.google.com/search?q=cray+%22folklore%22+site%3An...](https://www.google.com/search?q=cray+%22folklore%22+site%3Ansa.gov)

~~~
fentonc
It did! I actually got a nice reply from Whitfield Diffie, basically saying
"Haha, no." They have what amounts to a never-declassify-anything-digital
policy. I got a similar letter from the NNSA.

Through a friend-of-a-friend, I did actually manage to get a copy of the
source code to CTSS, the cray time sharing system, on microfiche from Lawrence
Livermore National Lab, and I even had it digitized (but not OCR'd), but it's
written in a language called COMPASS i've never found a compiler for.

~~~
greenyoda
COMPASS was the name of the assembler language for the earlier supercomputers
that Seymour Cray designed while he was still working at CDC, such as the CDC
6000-series:

[https://en.wikipedia.org/wiki/COMPASS](https://en.wikipedia.org/wiki/COMPASS)

~~~
fentonc
I misremembered, I think the CTSS source was actually written in a language
called LRLTRAN. I just remembered it was something obscure.

~~~
tjalfi
LLNL used to have LRLTRAN manuals online. It's an extended Fortran-66 for
Systems Programming.

------
nwallin
> This has some interesting implications – there’s no ‘divide’ instruction,
> for instance, because it can take a variable amount of time to finish. To
> perform a divide, you need to first compute the ‘reciprocal approximation’
> (something we _can_ do in exactly 13 cycles, it turns out) of the
> denominator value, and then perform a separate multiply of that result with
> the numerator.

Note that the special sauce behind this is the same as the special sauce
behind fast inverse square root. The integer bitwise components of a floating
point number permit a really good approximation of the log base 2 of it. And
once you have the log base 2 of a number simple arithmetic does interesting
operations.

log2(x^-.5) = -.5 \\* log2(x)

log2(x^-1) = -log2(x)

The same trick can be used to calculate any constant power over the range
[-1,1]. -.5 is the most famous for whatever reason, probably because of the
"what the fuck?" comment in the open source quake code.

I'm not entirely sure why this knowledge was known at Cray, then lost, and had
to be rediscovered at SGI or whatever. And I'm not entirely convinced it ever
was lost. But if it was lost, I imagine it had something to do with replacing
engineers whose bread and butter was done on a sliderule (which is inherently
built on the premise of manipulating logs of numbers) with engineers who
always had a pocket calculator.

~~~
HeWhoLurksLate

       > The same trick can be used to calculate any constant power over
       > the range [-1,1]. -.5 is the most famous for whatever reason,
       > probably because of the "what the fuck?" comment in the open. 
     >  source quake code.
    

That was an interesting read, thanks!

------
duskwuff
> The actual design was implemented in a Xilinx Spartan-3E 1600 development
> board. This is basically the biggest FPGA you can buy that doesn’t cost
> thousands of dollars for a devkit.

Note that this bit is rather outdated. :) The FPGA on an entry-level
development board (like a Xilinx Artix-7 35T) is comparable in size -- as well
as much faster! -- and you can go even bigger without stretching your budget
too much.

If you're willing to get a little adventurous, in fact, you can get an FPGA
that's over _ten times_ the size for under $200:

[https://www.aliexpress.com/item/32907109444.html](https://www.aliexpress.com/item/32907109444.html)

~~~
fentonc
I really need to make an updated blog post about it, but this project evolved
into a reasonably-well-debugged Cray J90 core that fits quite comfortably in a
Xilinx Artix-7 35T board (I made a somewhat bulky Cray J90 Smartwatch that
tells time by running a real-time n-body simulation of Jupiter and 63 of its
moons . . . inferring the current time is left as an exercise for the viewer).

~~~
pstuart
I could only aspire to such awesome geekiness. Thank you for making the world
a more interesting place.

------
dang
For the curious, the past threads with one or more comments appear to be:

2018:
[https://news.ycombinator.com/item?id=16756994](https://news.ycombinator.com/item?id=16756994)

2014:
[https://news.ycombinator.com/item?id=8447518](https://news.ycombinator.com/item?id=8447518)

2013:
[https://news.ycombinator.com/item?id=6291515](https://news.ycombinator.com/item?id=6291515)

2012:
[https://news.ycombinator.com/item?id=4561787](https://news.ycombinator.com/item?id=4561787)

2011:
[https://news.ycombinator.com/item?id=2621177](https://news.ycombinator.com/item?id=2621177)

2010:
[https://news.ycombinator.com/item?id=1645291](https://news.ycombinator.com/item?id=1645291)

~~~
djmips
People are so weary of this that there aren't even the usual requests to put a
date on the title of the original post.

~~~
m463
It's like the story of the ground speed check from the SR-71 pilot.

(on the other hand, this is the first time I heard about the cray replica)

------
dboreham
One of my wife's (of 20+ years) pickup lines, that worked, apparently, on me
was she said she could get me in to sit on a Cray-1.

------
TomVDB
The recovery of the data from the HD is particularly impressive:

[http://www.chrisfenton.com/cray-1-digital-
archeology/](http://www.chrisfenton.com/cray-1-digital-archeology/)

------
chrisulloa
> computational necromancy

Haven't you read laundry files? You could accidentally summon an alien horror
from another dimension.

~~~
gpderetta
Did you see the shape of that thing? It obviously hides a well grounded
summoning grid.

------
ralphc
The Computer Museum of America, in Roswell, GA, has a large collection of
Crays. They may have, or can provide leads, on software.

[https://computermuseumofamerica.org](https://computermuseumofamerica.org)

~~~
linker3000
When I was working on a project (only a few weeks) at EPFL in Lausanne, they
had two or three of their old Crays spread around the campus as static show
pieces - maybe they still have some software.

------
IOT_Apprentice
Apple had a Cray X-MP at one point.

------
mark_l_watson
I used Cray and huge CDC mainframes way back when. Fun stuff.

That said, my Linux laptop with a 1070 GPU and CUDA does about seven trillion
float operations a second. For modern times, the old mainframes don’t seem
useful.

------
bytematic
They had to use a tall skinny woman and a short woman to hook wires up from
the inside. Shortest path between any point is the best way to increase speed.
Love cray, you get a case of beer when you buy one!

~~~
mark-r
I assume the beer was Leinenkugel's?

~~~
mark-r
For those unaware, Leinenkugel's is made in Cray's home town of Chippewa
Falls.

------
srcmap
Cray 1 was built 45 years ago. Iphone is 10x that system today.

Fun to imagine what the computer might look like 45 years from now - everyone
will have a gigabits quantum computer in their pocket?

~~~
joefourier
Do note that that blogpost is almost ten years old. At peak power, the latest
iPhone is now probably around 3000x faster than the Cray 1 if you count the
GPU (although finding FP64 performance stats for the iPhone is bit
challenging).

------
KingFelix
This is awesome and I want to build one for my home, inside of a Tardis

~~~
jdkee
IIRC, a working Cray inside of a traveling Tardis collapses the whole thing
into a black hole.

------
aj7
Heh heh. “Sure, your iPhone is 10X faster, and it’s completely useless to own
one, but admit it . . you really want one, don’t you?”

NO, I want an 11 Pro with them three cameras!!

(But I am waiting for someone to emulate a Cray on a phone.)

~~~
pmiller2
I actually think gutting one of the cases to use as a couch would be super
awesome. It could definitely be the centerpiece of a living, room, den, or
home office.

~~~
pugworthy
Facing apart from each other, it's more like something you put in the middle
of the room during parties - so all the people watchers can sit there and look
out, but not interact with each other.

~~~
rs23296008n1
Make it rotate. Add a light show. See the whole room. Bonus points when people
get drunk/"altered states".

~~~
pfdietz
Turn a Cray-2 into an actual aquarium.

~~~
Mountain_Skies
Be sure to stock it with crayfish.

