4 Oct
2016
4 Oct
'16
3:02 p.m.
From: Al Kossow <aek at bitsavers.org>
the will probably be 68000
unisoft kernels i've used weren't 010 with the 451
Dumb question...did the '451 have a mechanism to work around the
instruction restart issue in the 68000? Or was there some other way
that was handled?
i'll have to dig around for what bits of the 451
kernel i still
have around. unisoft kept the mmu parts pretty well isolated since
the did so many hw ports
I'd be grateful.
KJ
4 Oct
4 Oct
3:14 p.m.
On 10/4/16 3:02 PM, Ken Seefried wrote:
Dumb question...did the '451 have a mechanism to
work around the
instruction restart issue in the 68000?
no. the 68451 is a segmented mmu, so you wouldn't use it for demand
paging. the normal way you use it in unix is setting up segents for
text, data, and bss
8:28 p.m.
On Tue, Oct 4, 2016 at 3:14 PM, Al Kossow <aek at bitsavers.org> wrote:
On 10/4/16 3:02 PM, Ken Seefried wrote:
I remember reading the spec sheets for a MMU of that type - for the 6809!
That was one versatile little processor.
--
Ian S. King, MSIS, MSCS, Ph.D. Candidate
The Information School <http://ischool.uw.edu>
Dissertation: "Why the Conversation Mattered: Constructing a Sociotechnical
Narrative Through a Design Lens
Archivist, Voices From the Rwanda Tribunal <http://tribunalvoices.org>
Value Sensitive Design Research Lab <http://vsdesign.org>
University of Washington
There is an old Vulcan saying: "Only Nixon could go to China."
Dumb question...did the '451 have a mechanism
to work around the
instruction restart issue in the 68000?
no. the 68451 is a segmented mmu, so you wouldn't use it for demand
paging. the normal way you use it in unix is setting up segents for
text, data, and bss
5 Oct
5 Oct
1:15 a.m.
On Tue, Oct 4, 2016 at 3:14 PM, Al Kossow <aek at bitsavers.org> wrote:
no. the 68451 is a segmented mmu, so you wouldn't
use it for demand
paging. the normal way you use it in unix is setting up segents for
text, data, and bss
On Tue, Oct 4, 2016 at 9:28 PM, Ian S. King <isking at uw.edu> wrote:
I remember reading the spec sheets for a MMU of that
type - for the 6809!
That was one versatile little processor.
I've never heard of a segmented MMU for the 6809. The MC6829 MMU was
paged, using 2KB pages.
30 Oct
30 Oct
10:15 a.m.
Ian,
Sorry I took so long to respond, I have been out of town. I designed a plug in board to
upgrade the ROM slot to an EPROM but a quick look did not tune up any extras.
I am going to do a serious downsizing my collection and maybe we can work something out.
Michael Holley
206 484 1181
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Ian S. King
Sent: Tuesday, October 04, 2016 8:28 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: mc68010+mc68451 Unix source?
On Tue, Oct 4, 2016 at 3:14 PM, Al Kossow <aek at bitsavers.org> wrote:
On 10/4/16 3:02 PM, Ken Seefried wrote:
I remember reading the spec sheets for a MMU of that type - for the 6809!
That was one versatile little processor.
--
Ian S. King, MSIS, MSCS, Ph.D. Candidate
The Information School <http://ischool.uw.edu>
Dissertation: "Why the Conversation Mattered: Constructing a Sociotechnical
Narrative Through a Design Lens
Archivist, Voices From the Rwanda Tribunal <http://tribunalvoices.org>
Value Sensitive Design Research Lab <http://vsdesign.org>
University of Washington
There is an old Vulcan saying: "Only Nixon could go to China."
Dumb question...did the '451 have a mechanism
to work around the
instruction restart issue in the 68000?
no. the 68451 is a segmented mmu, so you wouldn't use it for demand
paging. the normal way you use it in unix is setting up segents for
text, data, and bss
5 Oct
5 Oct
1:22 a.m.
On Tue, Oct 4, 2016 at 4:02 PM, Ken Seefried <seefriek at gmail.com> wrote:
Dumb question...did the '451 have a mechanism to
work around the
instruction restart issue in the 68000? Or was there some other way
that was handled?
The MC68451 was just an MMU. The bus fault problem of the MC68000
can't really be solved by an MMU; solving it in the general case
requires a LOT of external logic, and/or a second MC68000. The Apple
Lisa solved it in a specialized way by writing the software to never
perform accesses from which bus fault recovery might be needed, except
using a specific instruction which yielded predictable bus fault
results.
The MC68010/012, MC68020, and MC68030 didn't support instruction
restart, but they supported instruction continuation, by having a bus
fault or address error dump a lot of internal processor state onto the
stack (known lovingly as the "stack puke"), and having the RTE
instruction reload it.
IIRC, the MC68040 and MC68060 supported instruction restart.
I once wrote an address error handler for the MC68020 so that I could
execute misaligned code. Very very slowly.
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aek＠bitsavers.org -
isking＠uw.edu -
linimon＠lonesome.com -
seefriek＠gmail.com -
spacewar＠gmail.com -
swtpc6800＠comcast.net