Subject: Re: Matrox
To: Jason Thorpe <thorpej@nas.nasa.gov>
From: David A. Gatwood <dgatwood@mvista.com>
List: port-macppc
Date: 08/15/1999 19:41:44
On Sun, 15 Aug 1999, Jason Thorpe wrote:

>  > The BSD and Mach development is closely intertwined.  For example,
>  > NetBSD's old VM was, AFAIK, Mach VM, and last I knew, FreeBSD still used
>  > Mach VM.
> 
> I think you have this a little backwards.
> 
> The Mach VM system, which was developed completely independent of BSD,
> was adapted for what became 4.4BSD because it had some features not present
> in BSD VM.  The VM that appeared in 4.4BSD was based on Mach VM, but had
> some differences, mostly dealing with differing kernel infrastructure.


Just to pick nits... ;-)  Technically,the VM system wasn't developed
independently of BSD, if I'm to believe the timeline of when the BSD code
became part of Mach.  It was developed independently of the BSD
_developers_.  It still had to service BSD code in the early kernel, which
would no doubt have been a design consideration (I _hope_ :-).  Of course,
all this was when I was... probably still in elementary school, so this is
strictly what I've read.  Heheh.


>  > OSFMach's device driver interface is, IIRC, a derivative of that of the
>  > BSD unices (though they have diverged greatly since), and OSF Mach is even
>  > more closely interrelated, in that the PowerMac port contains more code
>  > ripped from NetBSD and FreeBSD than actually written by OSF or Apple.
> 
> We're talking about device drivers, etc.  Device drivers to not an OS
> make.  Mach is actually quite different from BSD when you get into the
> actual "OS stuff".

True.  BSD has a lot more of the "OS stuff".  I'm also not sure what BSD
does vis-a-vis processes and scheduling, as oposed to the whole tasks
thing, but I suspect that's different, especially if you are comparing
current BSD to current Mach.  Likewise, mach 3 and... Hurd, I think, has
the whole server-based design, but that can't be generalized to all of
the various Machs.

The entire point was that BSD and Mach were, at one time, very closely
integrated, and as such, Mach was designed to be similar, or at least
easily interfacable, to facilitate this integration.  Better?  :-)


David