To: edgee@cyberpass.net
Cc: pups@minnie.cs.adfa.oz.au
Subject: Re: PDP-11 Addressing Modes
References: <199804150309.XAA00267@renoir.op.net>
From: Tom Ivar Helbekkmo <tih+mail@Hamartun.Priv.NO>
Date: 15 Apr 1998 18:42:54 +0200
In-Reply-To: "Ed G."'s message of "Tue, 14 Apr 1998 23:09:26 -0400"
Message-ID: <86ogy3kpdd.fsf@barsoom.Hamartun.Priv.NO>
Lines: 28
Sender: owner-pups@minnie.cs.adfa.oz.au
Precedence: bulk

"Ed G." <edgee@cyberpass.net> writes:

> 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?

It's simply beautiful.  The PDP-11 architecture is the pinnacle of
16-bit computing, as the 6502 (the world's first RISC chip) is the
unchallenged champion of elegance in 8-bit microprocessors.  The
cleanliness and orthogonality of the PDP-11 is a wonder to behold.
To top it off, they also knew when to _break_ orthogonality to make
proper use of the addressing mode bit combinations that don't make
sense for use with the program counter.

A good friend of mine, for whom I have much respect, claims that the
PDP-10 is even more beautiful.  I can't comment on this, not knowing
that architecture, but myself I've seen nothing to challenge the '11.

Among more modern processors, I'm quite partial to Motorola's MC68K.
I also like the Transputer -- who doesn't?  As for microcontrollers,
I've worked quite a bit with the Intel MCS-51 chips, and enjoyed it.

For the definition of "butt ugly", see the Intel i386 and its ilk.

-tih
-- 
Popularity is the hallmark of mediocrity.  --Niles Crane, "Frasier"