[net.arch] Univac 1100 registers

feldman@umcp-cs.UUCP (12/08/83)

The Univac 1100 series has its registers at memory addresses 0 to 127.
While these locations are different from normal storage in that they can 
operate on the data in them and they are usually referred to by mnemonics,
they can be used just as if they were core if you want speed and have
some registers to spare.   



-- mark feldman --  UUCP  : {seismo,allegra,brl-bmd}!umcp-cs!feldman
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bhyde@inmet.UUCP (12/13/83)

#R:umcp-cs:-429500:inmet:2500009:000:680
inmet!bhyde    Dec 10 16:20:00 1983

In the 1108 that I learned to program on the fact that registers were
memory was only sort of implemented.  The I/O calls to the operating 
system if pointed at the "registers" would read/write the memory
that was really there, but the instructions would see the registers.
This was a lot fun for passing secret messages between processes.  A
note left in the memory under the registers could often be picked up
a week later, love that core.
  Of course the PDP-10 treated registers as low core, no self respecting
compiler would fail to implement a tight loop by coping the instructions
into registers and branching into them, it would make the operator's
eyes glow.				ben hyde