[TUHS] Introduction

Oliver Lehmann lehmann at ans-netz.de
Thu Jun 5 01:11:16 AEST 2008

Jose R. Valverde wrote:

> Dear Oliver
> 	Astounding work!

Thanks :)

While I'm puzzeling the html document together with my open questions
(not so much questions but not so easy - at least for me - i guess) to
present them here (yeah, fear! ;) just some answers...

> What reference source are you using for the reconstruction process?
> I bet you are having a look at the source code for Plexis sys3 in the 
> TUHS archives, and comparing with the stock sysIII from SCO, right?

I have Plexis sources and used plain SYSIII sources - yes. Sometimes
I also used V7 sources because it pointed out through the recovery
process that sometimes the V7 source matched more the implementation
in WEGA than the SYSIII implementation was.

> FWIW from the source trees from SCO and Plexis, the code layout was
> arranged by CPU. I'd bet the WEGA authors had access so SysIII sources,
> and if they'd gone through the pains to get it, then they might as
> well got both -or perhaps Plexis, which should have been more easy
> to get- to use as their codebase. So a comparison of both source 
> trees should yield useful insights from the differences between PDP11,
> VAX and Z8000.

The biggest problem here is the memory segmentation. Plexis has - as far
as I understand the code - no segmentation/non-segmentation support. It
only supports one memory segment like the other SYSIII implementation did
(please correct me if I'm wrong - I'm far away from being a professional
ZEUS introduced a flag in the user structure specifying if the user runs
a programm in the segmented or non-segmented mode which was based on what
C-compiler was used (or what ASM, PLZ/ASM, PLZ/SYS directive was set.). In
the segmented mode all 128 memory segments where used, in the non
segmented mode only one of those 128 segments (as far as I can remember
it was always segment 63) was used.

In plexis I didn't saw such logic. This creates problems when it comes to
memory access in the Kernel or such things like file execution where the
special s.out header has differences for segmented or non-segmented

the WEGA-Developer themself (I had contact to their kernel developer) just
took ZEUS and wrote "some" machine-specific kernel parts new. They never
had access to the ZEUS sources. Later after WEGA was in place they got
access to original V7 sources and modified/added stuff in WEGA. All
sources the WEGA guys used is available to me because I got access to the
Development floppies (containing also firmware sources and so on... ;))
It can be clearly determined which objects are still original ZEUS objects
and which where rewritten by the WEGA guys:

a) the libraries LIB1 and LIB2 are storing the file modification times
of the included objects. The original ZEUS objects are all dated in '83
or '84, all WEGA implementations are dated later beginning with '86 for
some ASM-based objects and '88 and '89 for C-based objects.
b) the original ZEUS libraries are all containing the SCCS ident string
char sys4wstr[] = "@[$]sys4.c		Rev : 4.2 	09/26/83 22:15:02";
whereas the WEGA-sources are not containing such "whatstring".

> It is also possible that the system was compiled with a 
> different (may  be earlier) version of the compiler that was later shipped. 

This might be the case - but I just don't hope so..

> BTW, there are other Z8000 UNIX floating around. Maybe one of them will
> shed some extra light.

I'm much interested about hearing more about this. I only knew ZEUS, even
Plexis came quite late to my ears.

  Greetings, Oliver

 Oliver Lehmann

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