[GTALUG] T-shirt Ideas

[D. Hugh Redelmeier]

"Parity is for farmers."  -- Seymour Cray

That's a famous quote that is hard to figure out.  It was from some
time in the 1960's.  This was after his CDC 6600 was released (without
parity) and before his CDC 7600 (which had parity).

- Cray is the most famous designer of supercomputers.

- "parity" has two meanings in this quote

- the main meaning is: extra memory bits to detect some memory or bus
  failures (ones with an odd number of bit-flips)

- the mainstream belief was that parity checking was really useful to
  detect when things have gone wrong.  In that era, lots of things
  went wrong.

- my interpretation is that Cray just didn't want to waste circuitry,
  ferrite cores, and speed on parity bits.  Why speed?  Because it
  would surely affect fan-out or fan-in of some circuits on the
  critical path of his processor, which would in turn affect how fast
  they could be driven.

  Other designers were more humble: they liked to know if the results
  were corrupt.

  Cray advocated running test programs once in a while to see if the
  processor was still working.  This would actually reduce the
  computation power available less than parity checking.

- I'm pretty sure that every current serious supercomputer uses not
  just parity but ECC.  This may not be the case for GPU computing.

- "parity" was also a term used to describe certain features of US
  farm subsidies of that era.  This (possibly fringe) paper
    <http://c457332.r32.cf2.rackcdn.com/pdf/the-freeman/0604Folsom.pdf>
  says:

	Two concepts in the AAA are fascinating. First is the idea
	that because farmers overproduce some crops the government
	ought to pay them not to grow on part of their land. Second is
	the idea of "parity," that farmers ought to be protected from
	falling prices by fixing them so that they were comparable to
	the purchasing power of their crop in the excellent years
	1909-14.

  Note that AAA was the US Agricultural Adjustment Act of 1933 or 1938
    <https://en.wikipedia.org/wiki/Agricultural_Adjustment_Act>
  This seems to have been part of Roosevelt's New Deal.

So: does this famous quote win the obscurity competition?

"Farmers buy computers too" -- Seymour Cray, after CDC 7600 was
introduced.

If you want to know more about Cray, here's a slide deck from Gordon
Bell (a great computer architect, practical and academic).
<http://research.microsoft.com/en-us/um/people/gbell/craytalk/>
It's from a talk given shortly after Cray's death.

Funny point: the abstract calls Cray "the ultimate "tall, thin
man"*." but the notes on slide three call him the penultimate one.  I
wonder who the ultimate one is if the notes are correct.