26 Aug
1999
26 Aug
'99
11:47 a.m.
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.
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!
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
26 Aug
26 Aug
12:28 p.m.
>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@shell.monmouth.com|pechter@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.
9250
days inactive
9250
days old
1 comments
2 participants
participants (2)
-
CLASSICCMP＠trailing-edge.com -
pechter＠pechter.dyndns.org