11 Sep
2015
11 Sep
'15
8:19 a.m.
On 2015-09-11 16:49, Warner Losh wrote:
On Fri, Sep 11, 2015 at 8:39 AM, Johnny Billquist
<bqt at update.uu.se> wrote:
Uh? What do that have to do with the PDP-11 architecture? Overlays are a
thing specific to the operating system and linker, and looks and works
differently in different OSes on the PDP-11, if they have them at all.
Mind you, even having said that, overlays are just a userland
implementation of demand paging. Conceptually they are dead easy.
Now, the overlay description language, as well as the capabilities in
RSX, can make people seasick. But once you've worked with them for a
while, you realized that most of the time it is not that tricky.
Johnny
On 2015-09-11 16:36, Noel Chiappa wrote:
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. 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.)