Subject: Re: NetBSD/pdp10 ?
To: Perry E. Metzger <email@example.com>
From: Lars Brinkhoff <firstname.lastname@example.org>
Date: 03/07/2002 12:38:35
"Perry E. Metzger" <email@example.com> writes:
> Brian Chase <firstname.lastname@example.org> writes:
> > NetBSD/pdp10 anyone?
> The machine only had 18 bit pointers. It is a little light in terms
> of real memory space -- only about a megabyte in a full Moby.
Those machines are clearly not suitable for a NetBSD port. Maybe
> Extended PDP-10 architectures have been built
I think many of the PDP-10 machines still in runnable condition would
be extended PDP-10s: KL10 model B, Systems Concepts clones, TOAD-1s.
The exception is of course the DECSYSTEM-2020 with the KS10 processor.
> I was rather fond of the processor series -- byte pointers were NEAT,
> and if you really want to purge C, the fact that not all pointers are
> the same length on a PDP-6 or PDP-10 is a big frightening change for C
This is not an issue in the GCC port. All pointers are exactly 36
* Byte pointers (char *, short *, etc) are in the one-word global
byte pointer format supported in hardware in the extended
architecture: the 6 most significant bits hold a "P&S" code, and
the 30 least significant bits hold a word address.
* Word pointers (int *, float *, double *, etc) are in the global
address word format. The 6 most significant bits are always
zero, and the 30 least significant bits hold a word address.
In some cases local (18-bit) addressing will be used as an optimization,
but this is not visible to the programmer.
Lars Brinkhoff http://lars.nocrew.org/ Linux, GCC, PDP-10,
Brinkhoff Consulting http://www.brinkhoff.se/ HTTP programming