Greybeards

[Gary Kline]

On Sat, Oct 23, 2010 at 01:15:05AM -0500, Robert Bonomi wrote:
> 
> 
> >Date: Fri, 22 Oct 2010 10:33:20 -0700
> >From: Gary Kline <kline at thought.org>
> >
> >	"TOS"?  <snicker>, LOL, ROFL ...
> 
> Yawp.  Really.  TOS and DOS.  Those _were_ the names the two OS varients
> were known by.  
> 
> Not too long thereafter, IBM decided the minimum configuration would include
> disk packs,  And 0S/360 became the universal choice.
> 
> 
> As for the 6400, it had 64k words of 60-bit  (each word could hold 10 
> characters in the internal CDC character set) memory.  roughly 2x to 2.5x
> the capacity of the 64k 32-bit words on the IBM.
> 
> I programmed on the 6400, and it's big brother, the 6600, for a number of 
> years.  An absolutely _lovely_ architecture  at a high level it was a 
> beatutifully simple architecture,  with a machine-language that you could
> learn in an afternoon, if you'd had any exposure to _any_ other assemler
> language.  The instruction set was _so_ rational, you didn't need a "cheat
> sheet" (aka, "green card", "yellow card", whatever) to keep track of what
> was what.
> 
> Now, admittedly, the closer you got to the hardware, the more "strange" the 
> machine got.  It's the only machine I know of, where "CPU HALT" is an
> _unpriviliged_ user-mode instruction. and one where user programs are 
> *expected* to use it to end every program.
> 
> And, of course, the 6600 architecture (the 6600 was the original model, 6400s
> were introduced later as a 'economy' version) as one other endearing 
> characteristic.  It *can't*add*.  At the hardware level, addition is done
> by 'complement and subtract'.  And  the CPU clock is more than 10x faster 
> than memory read cycle.  Memory is 32-way(!!) interleaved, to keep up.
> 
> Oh yeah, the machine -really- annoyed computer-science purists.  Up to
> the limit of data that you oult fit in main memory, an optimized _bubble-
> sort_ was faster than =any= other sorting algorithm.  This came as a *RUDE*
> surprise to more than one first-year C.S dept faculty member.  There was
> always some smart-*ss in the class who got the bubble-sort implementation
> "right", and it ran in far less time than even quicksort.   If you did
> _careful_ benchmarking, you could see that when the data-sets got large
> enough that the 'expected' (bubble-sort "loses") behavior _was_ there.
> but the cross-over/break-even point was at a point that was _larger_ 
> than the maximum main memory that you could hang on a machine with only
> an 18-hit address-space.  Uuser apps were limited to only 17 bits of
> addressing.
> 
> It also freaked some people that you could copy a dataset that was 
> many times the size of main memory, using only _one_ buffer, and isusing
> only *one* 'read" and *one* "write" instruction.  The operating system
> was 'management by committee' at the _hardware_ level, and could literally
> be doing _20_ different things simultaneously.   Start one member of the
> 'committee' transferring data from the 'source' into the buffer, and hav
> a -second- member transfering _out_ of the butter to the destination, 
> and just sit ack and watch them go at it.
> 
> The 6600 also gets credit for being the first CPU where speed-of-light
> limitqation had to be taken into consideration.  roughly 40% of the data
> "in" the CPU didn't have a fixed location,  but was 'in transit' to where
> it "would be" needed..  internal wiring of a particular insulation color 
> was _not_ 'field repairable'.  you had to remove the wire entirely, and
> replace it with a nother pice with the -specific- part number that came 
> from the factory.
> 

	Very interesting history.  I never knew that the wordsize was 60
	bits; hmm.  The 6600 was designed by Seymour Cray, as you
	prob'ly know.  Seymour was a hardcore EE who (at the time)
	thought that software was for pussies.  No-need-for.  No OS, no
	nothing.  Seymour only cared about speed.  

-- 
 Gary Kline  kline at thought.org  http://www.thought.org  Public Service Unix
    The 7.90a release of Jottings: http://jottings.thought.org/index.php
                           http://journey.thought.org