From: thad@btr.BTR.COM (Thaddeus P. Floryan)
Newsgroups: alt.folklore.computers
Subject: Re: FASTRANDs?
Date: 30 Jul 92 10:22:35 GMT
Organization: BTR Public Access UNIX, Mountain View CA

In article <1992Jul28.151227.5024@tandem.com> jime@Tandem.com (Jim Ellignsen) writes:
>I've never heard of a FASTRAND breaking loose and causing damage.  When
>I worked for UNIVAC we used to use FASTRANDs as a unit of measure as "in
>the house had a 6 FASTRAND basement".  How could something so big hold
>so little data?
>[...]

How could something so big ...   Hah!

I recall circa 1965 the UCB Project Genie machines (SDS 930) were adopted
by Tymshare Associates for use in their new timesharing service (yes, this
was before it later became known as Tymshare, Inc., which later begat Tymnet).

The disks were manufactured by, I believe, Bryant, and each platter was
about 5 feet in diameter, and the disk arms were literally the length and
thickness of an adult human's arms.  The compressed air hoses were 1/4"
diameter plastic tubing fed by a LOUD compressor.

Required two CEs to lift and clean each platter; the platter stack was
somewhere between 15 to 20 platters (never could stay in the room long
enough (due to the noise) to count 'em :-)

For the trivia buffs, the SDS 930 became the SDS 940 and later the XDS 940
when Xerox purchased Scientific Data Systems.

The SDS 930 machines were "interesting": heated core memory.  Yes, deliberately
heated to about 130F due to the original market for these systems (the USA
military).  My understanding was they were used on the DEW Line (up in Canada)
and in places such as Kwajalein because:

	in Canada, the location of the DEW (Distant Early Warning) Line was
	so cold, the machines would otherwise freeze, and

	in Kwajalein (Marshall Islands) the humidity was so high that jungle
	rot would deteriorate the computer (thus the heater coils burned off
	the moisture).

These would not be "Environmentally Correct" systems to operate today! :-)

The swapping/paging device on the systems were Bryant Drums, also known as
RADs (Rapid Access Drums) with one head per track; these monsters appeared
like humongous gyroscopes.  An anecdote related to me by an SDS CE goes:
"one day in El Segundo CA (home of SDS) a drum once decided to abandon its
moorings and took off, plummeting and crashing through some 10 memory
cabinets before finally coming to rest."  Sheesh!  Think about it: a 1000 lb,
8" thick slab spinning at, what, 2700 RPM, taking off.  Whew.

Architecturally those were advanced systems, 24 bit word, with both 6-/8-bit
bytes depending how one thought of them.  Even permitted one to define one's
own instructions for the first 37 octal opcodes (a feature also present in
the DEC PDP-6, PDP-10 and DEC-20 systems as UUO's).  One could re-arrange
the memory page map with the ol' BRS 43 and BRS 44 system calls.  Neat.

Circa 1968-1969 the old Bryant disks were replaced by an innovative Tymshare
"selector channel" based on the Varian 620i computers (which also were used as
the first "engines" for Tymnet) occupying only a single rack and could be
debugged dynamically while operating!  Contrast that with the equivalent
but considerably larger IBM SC at $300,000 (the 620i-based SC was only $80K),
and the fact the IBM unit couldn't be debugged (the same way) in real-time.
Both SCs operated banks of IBM 2214 (not sure of this model number) 10-high
platter assemblies which were only about 18" dia and about 10" high.

I'll curtail this article now and defer stories about funny things one could
do with Xerox Sigma 5, 7 and 9 computers to another article (hints: concerns
the PSW, the memory map, and the I/O channels! :-) if anyone's interested.

Thad Floryan [ thad@btr.com (OR) {decwrl, mips, fernwood}!btr!thad ]
Newsgroups: alt.folklore.computers