Path: utzoo!mnetor!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!rutgers!gatech!hubcap!rchampe
From: rchampe@hubcap.UUCP (Richard Champeaux)
Newsgroups: comp.sys.amiga
Subject: Re: Hey, Commodore Sales:  Amiga 3000 Warning
Message-ID: <1359@hubcap.UUCP>
Date: 11 Apr 88 17:47:11 GMT
References: <7735@oberon.USC.EDU> <247@sdrc.UUCP> <930@rmi.UUCP> <61@kenobi.UUCP> <2503@unicus.UUCP>
Organization: Clemson University, Clemson, SC
Lines: 38
Summary: Is it as easy as you claim?

In article <2503@unicus.UUCP>, craig@unicus.UUCP (Craig D. Hubley) writes:
> 
> If you produce a Zorro III standard (32-bit, access to video, etc.),
> then it *must* somehow be able to support a Zorro II card, *in* the cage.
> 
> In article <249@sagpd1.UUCP> monty@sagpd1.UUCP (Monty Saine) writes:
> >2000 cards. Stop and think before you flame on. The 3000 will have a 32 bit 
> >bus and the 2000 has a 16 bit bus.
> 
> 	based on obvious incompetence.  The 68030 can retrieve 16-bit
> 	data, a 16-bit bus is just half of a 32-bit bus, nobody expected
> 	32-bit performance out of a 16-bit card, but they wanted at least
> 
> 	Craig Hubley, Unicus Corporation, Toronto, Ont.

     Your right, if the 68030 is anything like the 68020, it is capable of
dynamic memory port sizing, and would have no problem addressing a 16-bit
card.  However, if that card has DMA on it connected to some I/O device,
then it would need to be able to address the 32-bit memory that is most likely
to exist in an A3000.  Getting a card that is connected only to D0-D15 of the
address bus to access the odd addressed words connected to D16-D31 would
require extra hardware on each of the 32-bit memory cards that would allow
word swapping.  It might be possible to put such hardware on the system board,
but that would make it really complicated, and probably slow up the bus.
Another idea that was suggested by someone a few messages ago, was to include
some 16-bit memory for the 16-bit cards to use, but to do that, you would have
to require software wishing to use such devices, to place anything it wants
DMA'ed in the 16-bit memory.  Now your hardware is compatable, but your 
software doesn't work anymore.
     Anyways, if the A3000 is indeed aimed at the workstation market, and has
the accompanying price of $4000 plus, then the A2000 will still be a very
popular computer (probably more popular than the A3000).  I hardly think that
CA will drop, or that people will stop buying the A2000, so you won't have
to worry about companies dropping their Zorro-II cards.


Rich Champeaux
Clemson University