PDP-11 architecture Was: internet blocking problem ?

Warner Losh imp at bsdimp.com
Fri Sep 11 09:49:00 CDT 2015

On Fri, Sep 11, 2015 at 8:39 AM, Johnny Billquist <bqt at update.uu.se> wrote:

> On 2015-09-11 16:36, Noel Chiappa wrote:
>>      > From: Jon Elson elson
>>      > I actually LIKED the PDP-11 architecture quite a LOT, but the
>> limited
>>      > memory was a big killer.
>> The good thing about the PDP-11 was the 16-bit word size. (It resulted in
>> what's probably the most elegant architecture, in bang/buck terms, of all
>> time.) The bad thing about the PDP-11 was the 16-bit word size. (For the
>> reason you point out.)
> WHile I agree that the PDP-11 is a wonderful architecture, it really is a
> few bits short of perfect, both for addressing, and for opcode allocation.
> The is obvious when you look at the EIS and FPP extensions, which could
> not retain the general instruction layout format because of a lack of bits.

I loved the PDP-11 architecture, until I wanted to run programs on it that
relied on the overlay manager and the overlays got to be 8 or 9 deep. Then
it was... painful.


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