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Path: utzoo!mnetor!uunet!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: Zorro III (Re: Wishlist for A3000)
Message-ID: <2831@cbmvax.UUCP>
Date: Fri, 20-Nov-87 11:44:18 EST
Article-I.D.: cbmvax.2831
Posted: Fri Nov 20 11:44:18 1987
Date-Received: Sun, 22-Nov-87 11:08:07 EST
References: <1079@sugar.UUCP>
Organization: Commodore Technology, West Chester, PA
Lines: 36

in article <1079@sugar.UUCP>, peter@sugar.UUCP (Peter da Silva) says:
> Keywords: Commodore A3000 Do it RIGHT!
> 
> How about adding an extra 8 bits of address and 16 of data on a secondary
> bus in a similar fashion to the PC/AT bus? If you do it right it will
> be possible to use 16-bit cards in the new bus. Much simpler than
> going to NuBus.

Sure we can do something like that, and probably will.  But that's just the
obvious thing.  There are other issues to address in an advanced expansion
bus, like speed, multiple masters and DMA fairness, etc.  Also bus 
specification; NuBus is very simple and clearly tells you when to do each
and every thing; the current Amiga bus and the PC/AT bus are much more like
extensions of the CPU and, being that CPU interfacing isn't necessarily
designed to be extended as a bus, the bus interfacing on these busses is
tricker for designers to do right.

NuBus, VME, and MicroChannel all address these issues to some degree or
another, though I'm not at all convinced that any one of them does it right
(especially MicroChannel...).

> A side question: since NuBus slots are at fixed addresses, is it technically
> a bus?

Sure.  It's a geographically addresses bus.  Makes much more sense in the case
of a 4 gigabyte address space than it does in the case of a 16 megabyte
address space.  Amiga Autoconfig is the best way I've seen to configure cards
in the latter case.

> -- Peter da Silva  `-_-'  ...!hoptoad!academ!uhnix1!sugar!peter
> -- Disclaimer: These U aren't mere opinions... these are *values*.

-- 
Dave Haynie     Commodore-Amiga    Usenet: {ihnp4|caip|rutgers}!cbmvax!daveh
   "The B2000 Guy"              PLINK : D-DAVE H             BIX   : hazy
		"I can't relax, 'cause I'm a Boinger!"