24 Feb
2003
24 Feb
'03
6:40 a.m.
Hello again from Gregg C Levine
I've got a PDP-11/53 on order, call it. Would that board work there?
And where could I find one of these, RX02 (DSD 4140) board(s)? Also,
what exactly is this RX02 (DSD 4140) board? Its one that I don't quite
remember hearing about.
-------------------
Gregg C Levine hansolofalcon(a)worldnet.att.net
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-----Original Message-----
From: pups-admin(a)minnie.tuhs.org [mailto:pups-admin@minnie.tuhs.org]
On
Behalf Of Jonathan Engdahl
Sent: Sunday, February 23, 2003 11:33 PM
To: cctech(a)classiccmp.org; pups(a)minnie.tuhs.org
Subject: Re: [pups] Re: PDP11 - RQDX1 standalone format utility? -->
XXDP
Now that I think of it,
this case
000137
145702
is wrong too. Assuming that the program is relocatable (which in it probably is not), and you simply loaded the entire
file into
memory, it
would be offset by the 16 byte header, so you would
want to jump to
145722.
I think I will remove that patch at 20 altogether.
Did you know that the output from PDPXASM can be loaded to a barely
twitching PDP-11 via VTserver? I used PDPXASM to write scope loops
for an
RX02 (DSD 4140) board I resurrected.
--
Jonathan Engdahl
http://users.safeaccess.com/engdahl
"The things which are seen are temporary,
but the things which are not seen are eternal." II Cor. 4:18
----- Original Message -----
From: "Michael Davidson" <michael_davidson(a)pacbell.net>
To: "Jonathan Engdahl" <j.r.engdahl(a)adelphia.net>
Cc: <cctech(a)classiccmp.org>; <pups(a)minnie.tuhs.org>
Sent: Sunday, February 23, 2003 4:40 PM
Subject: Re: [pups] Re: PDP11 - RQDX1 standalone format utility? -->
XXDP
> Jonathan Engdahl wrote:
>
> >I documented the procedure to extract a program from XXDP and put
a
header
> >on it so that you can boot it from VTserver or a UNIX disk. It
has been a
> >long time since I did this to ZRQCH0, so I
practiced on the
program that
I
> >think Christos needs (ZRQBC1) and sent it to him.
> >
> >There's a lot I don't know about the a.out header, so if someone
can
improve
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my method,
let me know.
http://users.safeaccess.com/engdahl/xxdp.htm#hackXXDP
There isn't very much to know about the a.out header,
and what you are doing looks OK although I would probably
have set a_text to 160000 and left a_data and a_bss as 0.
While I am not really familiar with the BSD boot code that
vtserver uses when loading a program I am almost certain that
it will use the entrypoint address in the a.out header and
not just jump to address 0. (remember it's an actual program
loader that understands a.out format, not just something that
only knows how to load a boot block and jump to it)
This is confirmed by the fact that the code you are patching
into the image at address 0 is wrong if you want it to get
you to the restart address.
In your example you have:
000020/ 000167
000022/ 145702
If this was loaded at address 0 in memory and the boot code
jumped to address 0, you would end up at 145706 *not* 145702
(of course, you might very well get lucky and still land on
an instruction boundary, but you would have skipped the first
2 words of the restart code).
If this code were really necessary (and I'm 99.99% sure that
it isn't) you would want either:
000137
145702
or:
000167
145676
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