Re: interative use, The Design of Design

According to Stephen Fuld  <sfuld@alumni.cmu.edu.invalid>:

With sufficiently disciplined programming, you could swap and move data
by updating the base registers.  APL\360 did this quite successfully
and handled a lot of interactive users on a 360/50.

>
Wasn't APL\360 an interpreter?  If so, then moving instructions and data
around was considerably simpler.

That's right.  It could switch between users at well defined points that
made it practical to update the base registers pointing to the user's workspace.

Reading between the lines in the IBMSJ architecture paper, I get the
impression they believed that moving code and data with base registers
would be a lot easier than it was, and missed the facts that a lot of
pointers are stored in memory, and it is hard to know what registers
are being used as base registers when.

>
Interesting.  That would seem to imply that it wasn't that they didn't
think about the problems that base addressing would cause, they just
(vastly) underestimated the cost of fixing it.  A different "design"
problem indeed.

In Design of Design, Brooks said they knew about virtual memory but thought
it was too expensive, which he also says was a mistake, soon fixed in S/370.

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