> >Making a processor is not hard (although FPGAs might make it harder than
> >just using simple TTL chips -- some of the manufacturer's claims on this
> >are plain false). I'd not try to re-implement the PDP11 unless you had a
> >good reason to do that -- rather, design an instruction set and
> >architecture and implement it.
Tim Shopa adds:
> I agree 100% here. *Especially* if your goal is to run NetBSD or Linux
> or (insert popular Unix-like free OS here). These OS's simply don't
> fit well into the 16-bit virtual address space of an -11 (2.11 BSD
> has many of the features of modern Unices, but doesn't have the wastage
> found in NetBSD or Linux).
>
> A small, RISC-ish instruction set is perfect for implementing NetBSD
> on. Things get a bit more complicated as you add the necessary memory
> management, of course!
>
I once started figuring out an instruction set of a PDP32.
Thirty two bit wide registers, 32 registers in two register sets...
A PDP11 compatibility mode using half of the registers.
Kind of a cross between the PDP11 and VAX11 without the complex stuff
like Packed instructions and such.
I kind of wonder if one could be built and designed to work with an
extended virtual address unit that could map to 11/70 par and pdr
relocations and run multiple virtual 11/70's under it.
Bill
---
bpechter_at_shell.monmouth.com|pechter_at_pechter.dyndns.org
Three things never anger: First, the one who runs your DEC,
The one who does Field Service and the one who signs your check.
Received on Thu Aug 26 1999 - 19:28:49 BST