> * RC5Stint <rc5stint@yahoo.com> on Tue, Jul 17, 2001:
> >
> > This is what I know.  I gleaned it from reading the archives
> > for this and other Dreamcast development lists, and reading
> > some sites out there.
>
> Hehe, no offense, but I think some of it is also "wishful thinking" :P.

Probably. ;-)

> There are a few "buses" that operate in the DC, the PVR2 and a couple of
> other things sit on one (again, see the DC tech pages, I can't access them
> now), and the AICA system, GDC, and expansion port sit on the other.  I
> still don't know which one is G2 and which one is G1, but I think Maple
> belongs to G2.  The bus that the AICA & expansion port sit on runs at
> 66Mhz, a bit slower than devices on the G2 bus ;-).
>
> > [Inside Dreamcast][              Inside BBA or modem      ]
> > [   Maple bus -->][bridge -> PCI bus -> NIC or modem chips]
> >
>       ^^^^^
>       G2/G1 bus (see DC Tech Pages - I forget which is which)

So what you are saying is that I made a mistake thinking that there was only
one system-wide bus, and that it was called Maple?  If so, then good; that
means I'm not totally cracked! :-/

> > You could take the modem apart and use the bridge chip in your
> > own projects.
>
> I've never heard of anyone doing this.  That's why I called it
> "wishful thinking" above.

I never heard of anyone doing it either.  I only said it was worth a try.

It makes sense that the Dreamcast to PCI glue chip is different in the modem
than in the BBA.  These devices were probably built in a hurry, and no one
had the time to build a real PCI bridge.  They probably built the modem
first, and thought they weren't going to glue another PCI device to the
Dreamcast.  And then came the BBA. ;-)

If they had known they were eventually going to bridge two devices, they
might have built a more generic PCI glue chip when they built the modem, and
have it available for the BBA, and in case other PCI devices had to be
bridged.  Well, that's what I would have done. :-p

> > Or you could build your own bridge, and map as many quantities
> > of devices and as many different bus types to the Maple bus as you want.
>
> That's a plausible theory - but it's never been tested or verified, AFAIK.

I never claimed it was verified.  And this I admit might be a bit too wild a
possibility.  Some buses might not map too well to Dreamcast for a lot of
reasons.  So that limits the "many different bus types" available.

Yet certainly some bus combinations are possible.  ISA and PCI, for example.
bITmASTER recently updated his pages, and claims he has PCI and PCMCIA
working.

> The authoritive source (hehe, for DC hacking? ;-) on this would be Marcus
> Comstedt, who has done the most (publicly, at least) in reversing DC
> hardware.  You also might want to try bITmASTER, or the gents on this list
> who actually built the ISA/IDE interface.  They'll explain it
> better than I could ;-).

These sources were the ones I was referring to.  I should have verified my
assumptions before posting, but I was certain I was correct.  And it seems
my biggest sin was getting the bus name wrong.  Thinking there was only one
bus instead of several, would not have been so bad, if I had gotten the name
right. ;-)

Ok, I think my ideas, your corrections, and the sources you mentioned,
should be enough to direct someone down the right path.  I'm done talking
about this, before I make a bigger fool of myself!

RC5Stint