PDP-11 Addressing Modes
Tom Ivar Helbekkmo
tih+mail at Hamartun.Priv.NO
Thu Apr 16 02:42:54 AEST 1998
"Ed G." <edgee at 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"
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