Re: The Design of Design

Thomas Koenig wrote:

snip

 
However, one questions.  Designs like the PDP-10 or the UNIVAC
(from what I read on Wikipedia) had "registers" at certain
memory locations.

Univac reserved the first 0200 locations of the user's address space as
"aliases" of the registers.  This is because the instruction format
only had room for one arithmetic register and one indes (address)
register.  Thus to, for example, load one register with the contents of
another, you put the source register's address in the displacement
field.  But physically, the regoisters were separate.


In fact, on the 1108, since the first 0200 memory locations weren't
diretly usable by the software, they were reserved such that upon a
system power loss, the actual CPU registers were saved into those (core
- hence non-volatile) memory locations so at least in theory, you could
recover from a power loss.  It didn't work very well.



--
 - Stephen Fuld
(e-mail address disguised to prevent spam)