Future of SCO UNIX

[Sean Eric Fagan]

In article <T.-7497 at xds12.ferranti.com> karl at ficc.ferranti.com (Karl Lehenbauer) writes:
>In article <35 at unigold.UUCP> lance at unigold.UUCP (Lance Ellinghouse) writes:
>Since even V.3 has Xenix 286 and 386 binary compatibility, what's the point?
>V.4 even has BSD compatibility -- you later mention running a BSD emulator too.

*Size*.  Mach is a *lot* smaller than 3.2 (stock, ISC, ESIX, SCO, whatever).
Yes, if you throw in the unix emulator, the system will increase in size.
But:  you can make the unix emulator a part of the user space, not the
kernel.  You can upgrade your unix emulator a lot more easily than you could
upgrade your current unix kernel (I hope 8-)).  Joe Blow could have a strict
SysV environment, while A. R. User could have a strict BSD environment
(meanwhile, everyone else would be running a SysVr4-ish environment).  And
the stuff being used is all that's paged in.  Device drivers in Mach can be
paged.  You have the option of multiprocessing in Mach (supposedly; I know
that, a while ago, there were problems with this, and I don't know if they've
been fixed.  If SCO were to go to Mach, that would undoubtedly be one of the
things fixed [probably by Corollary, though, I guess]).  Theoretically, one
could come up with an OS/2 server (why one would want to is beyond me, but
one knows that there are some pretty strange people out there), which you
cannot do under unix (well, you could, but it's not easy, and the penalties
involved would probably be too much).

Etc.

SysVr4 needs 8Mb to install.  I doubt it's going to be terribly happy in
anything less than about 6Mb.  A version of Mach 3.0, with both SysV and BSD
emulators, would probably fit in that space a *lot* better.  (Mainly because
the Mach memory manager seems to be better than the SysVr4 one.)

>IBM did something similar called VM.  It
>provides simulated hardware to run multiple operating systems rather than 
>the set of software services Mach provides.  Something of a performance hit
>there.  

Yes.  VM is a bit much.  Although you can simulate OS's under Mach, you do
so by writing an emulator, something that will deal with the traps of the
application and do whatever necessary to support them.  You cannot just
fork off another copy of /vmunix (pun intended 8-)).

I.e., the OS simulation is from an application point of view, not an OS
point of view.

Your comments about this stuff not necessarily being easy are (probably)
correct.  But, then, dealing with a monolithic kernel such as SysVr4 isn't
easy, either.  The former at least offers the advantage of starting from
scratch, rather than adding on (and on and on and on and on...).

-- 
Sean Eric Fagan  | "I made the universe, but please don't blame me for it;
sef at kithrup.COM  |  I had a bellyache at the time."
-----------------+           -- The Turtle (Stephen King, _It_)
Any opinions expressed are my own, and generally unpopular with others.