Re: S/390 (was Market pressures for more reliable software)

[robin <robin_v@bigpond.nospam.com>]

Roedy Green <roedy@mindprod.com> writes: > On Thu, 28 Jun 2001 04:01:02 GMT, robin <robin_v@bigpond.nospam.com>
> wrote or quoted :
> 
> >> To load you had to adjust all the
> >> address references to account for where in RAM the program was loaded.
> >
> >No, only those words that had been specified as containing an absolute
> >address.
> 
> you only had a 12 bit displacement, so you needed great many ADCONS
> (address constants),

I'm aware that the displacement is 12 bits, having used the
assembley language for many years.
However, my original post mentioned program-relative addressing
as one of the modes.  With the BALR instruction, one or
more registers can be loaded with the absolute address of the next
instruction.  This register(s) can then be used as the
base register(s).  No address constants needed.

The number of address constants depends on the programmer.
There might be none or very few such constants.  Certainly not enough to
significantly increase program load time.

> to fill your base registers with before you could
> get at anything. On load, all these had to be adjusted to account for
> where the program was actually loaded in RAM.

Several instructions, requiring very little execution time.

> Roedy Green, Canadian Mind Products