PDP-11 Addressing Modes

[Johnny Billquist]

On Tue, 14 Apr 1998, Ed G. wrote:

> The first line of chapter on addressing modes in the *processor
> handbook* states:
> 
> "In the PDP-11 family, all operand addressing is accomplished through
> the eight general purpose registers."
> 
> If I understand correctly, even things like immediate operands and
> addresses are represented as an addressing mode of a register, namely
> the PC.  I think this is quite cool.
> 
> What do people here on the list think of the flexibility and 
> generality of the PDP-11's addressing modes?  Is this a well thought
> out architecture in your view?  How are the PDP-11's addressing modes
> better or worse than those of other processors, past and present?

The PDP-11 did it right, all others did it wrong. :-)

Well, at least as long as you're talking about general register machines.
(And points could be made that the M68K isn't very general about its
registers...)

For accumulator machines, I guess the vote goes to the PDP-10.

All with a big :-) of course. This is religion...

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt at update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol


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