🚀 go-pugleaf

In article <4452@ttidca.TTI.COM> hollombe@ttidcb.tti.com (The Polymath) writes:
>From foggy memory:

Let me clear some of the fog!  :-)
[Seriously, I'm not trying to show off or criticize, I'm just trying to
gently correct minor mistakes.  No insult intended.]

>Physically, each AP-101 consists of two metal boxes (very) roughly 1' x
>1.5' x 3', each and weighing about 90 lbs, each.  My memory gets much
>foggier here, but I recall one box is the CPU and the other is sort of a
>giant math co-processor.  The boxes are connected by a 2" diameter cable.

The second box is the IOP (Input/output processor).  I don't think it does
any math crunching.

>Mass data storage is provided by the Main Memory Unit (MMU), a mag-tape
                                      ^^^^
                                      Mass Memory Unit.

And there's actually two of them (they are identical, with identical
copies of the software on separate tapes).  On the panel that controls the
GPC's (O-6), you can select which MMU that a given GPC should read from.

By the way, it takes a non-trivial amount of time to load a program in
from the MMU (as you would expect).  The ascent software is in parts.  For
launch, only the software needed for a nominal ascent is in primary
memory.  If they have to abort RTLS (return to launch site) or TAL
(trans-atlantic abort), they have to load a different program in from the
MMU.  This does not sit well with some people, and it is one reason they
want to extend the memory capacity of the machines.

Funny MMU story.  One of my wife's former DPS co-workers called her one
day not too long ago and told her that someone he knew was doing a school
report on the Shuttle's MMU.  He asked her if she could send this person
as much information on the MMU's as she could find (and that would be
intelligible to someone without an in-depth knowledge of the shuttle).
She was bit baffled by this:  why would anyone care about the MMU's?  But
she honored his request anyway.  About a week later, he called back and
apologized.  Seems that this student wanted information about the Manned
Maneuvering Unit, *not* the Mass Memory Unit.  But if you say "MMU" to
someone who works (or in his case, recently worked) in DPS, their first
thought is "Mass Memory Unit"!  Can you say "acronym overload"?

			William LeFebvre
			Department of Computer Science
			Rice University
			<phil@Rice.edu>