direct I/O access

[Mike Meyer]

In <20070531084755.816A61C0008F at mwinf1907.orange.fr>, rmgls at wanadoo.fr typed:
> On Wed, 30 May 2007 12:39:10 -0400, Mike Meyer <mwm-keyword-freebsdhackers2.e313df at mired.org> wrote,
> 
> > Actually, protected mode is just the beginnings of it. I've never done
> > much x86 assembly, but going from the '020 to the '030 (or maybe it
> > was the '010 to the '020).  I had to start invalidating the hardware
> > caches after certain operations. After that, I switched to RISC
> > hardware, which were designed assuming that the real people writing
> > assembler would be few and far between, and did crazy things like
> > rearrange the instruction sequence behind your back and add extra
> > instructions. Modern systems do this kind of stuff as well.
>  
> do you think that it would be better to rewrite the soft in C???
> in this case, i have more work to do!
> first of all, learning C on the finger tip, before working on my soft.
> 
> and i thought that it would be very interesting to learn 
> the heart of FreeBSD.

Well, if you want to learn "the heart" of FreeBSD, I think you'd be
better off working in C. The code that isn't part of FreeBSD on pretty
much every platform would seem to be disqualified as the heart.

> > This really is a kludge, though. You haven't said what you're trying
> > to do. If you're trying to keep an old one-of device working, this is
> > probably the best way. But if it's a real device that other people
> > might be using, then writing a real device driver, or seeing if you
> > can make the device work with something like the iic drivers might be
> > better.
> 
> in fact, they are:
> - a direct to disk recorder,
> - a sampler.
> 
> they are not usable by other people, because they were discontinued.

So nobody else has them? You can't pick one up used on eBay? I
personally tend to run all but my most critical servers on
"discontinued" hardware. It's fast enough to do the job running
FreeBSD, and reasonably reliable; it's just not fast enough to run
modern versions of Windows. And I can buy a system and a hot spare for
a fraction of the cost of a new system.

	<mike
-- 
Mike Meyer <mwm at mired.org>		http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.