On Tue, 5 Sep 2000, Allen Briggs wrote:

> > Well as I understand it the 68k macs boot from their ROM - hence to
> > completely replace MacOS, you have to replace the ROM. Knowing apple,
> > there are probably no guidelines on how to do this. Macs just weren't
> > designed to boot anything except MacOS...
> 
> This is almost the case.  IM V published information about how it looks
> like you could boot a separate OS by putting the proper boot code in
> the proper place.  However, I don't think it's been used and I expect
> that it has problems...  Some of which have been outlined here.
> 
> If I recall correctly, the basic outline is that the ROM will find
> the boot disk, then will read the partition map and find the boot
> partition.  It will then (optionally) attempt to read a block of
> code from the disk to a given address and execute that code.  If
> that code was a first-stage boot loader, it could call some ROM
> routines to load a second-stage boot loader, and we could then boot
> fairly effectively from that.
> 
> As folks have noted, though, the ROM is often buggy and patched by
> the OS (although the base ROM is probably "good enough" for getting
> booted--buggy ROMs won't affect us except for the MRG where we don't
> get the ROM patches anyway).
> 
> As someone else noted, we don't have full MacOS services at this point
> in the boot and can't, for example, turn off video interrupts on nubus
> cards reliably (or as reliably as we can once things are booted).  This
> is true, but we do already know how to clear nubus interrupts on quite
> a few video cards (even if we don't know anything else about them ;-).
> 
> Of course, it would be nice to able to get rid of the MacOS pre-boot,
> but it would be quite a lot of work, and there are other things that
> would be worth more to most BSD/mac68k (or Linux/mac68k) users.
> 
> For example: better sound drivers, more OSS/IOP support (linux has
> working keyboard/mouse with IOP--we just need someone with time &
> skill to get it working for BSD), improved/fixed SCSI drivers,
> improved video support (Michael Zucca has been working on this for
> four years or so--maybe it's close to being ready for prime time? ;-),
> better interrupt scheduling, etc...
> 
> -allen
> 
> 

Of course, I'd love to help patch the kernel and improve the NetBSD
kernel, since it is my favorite OS. But the fact is, I'd don't know *jack*
about hardware or any OS kernels. I don't know Asm for any system, but
however I do know C. The problem is is that there is no where to go on the
Internet to find out how the BSD kernel works with information on what the
heck are video interrupts, OSS/IOP support, hardware I/O, etc. At least I
don't know a site that describes all of this in understandable English. 
There are
books describing it, but personally I don't have the moolah. And what if
the book is too technical that I can't understand the answer or that it
doesn't even contain the answer? I'm stuck with a book that I've wasted
money on and I don't have the material I want. Believe me, I do have
wasted $120 on books I'll never read. One can go to Barnes and Noble and
look at a book and see if it is the one I want, but Barnes and Noble
doesn't even have a book on OS structure or 68K hardware. I can't even
find a comprehendable book on 3D rendering there. Having that kind of info
on
the Web
is much more easier, less expensive, and more "friendlier" (i.e., I can
search for a piece of text on a site, whereas in a physical book that's
impossible). This is the only barrier which causes my ignorance - the lack
of material on understanding all of this (OS design, hardware,
etc.). Otherwise, I wouldn't be typing this - I would be patching up the
kernel.

Samad
"Ignorance is bliss." - Calvin
"I'm not sure I can handle all this bliss." - Hobbes