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From: bryce@COGSCI.BERKELEY.EDU (Bryce Nesbitt)
Newsgroups: comp.sys.amiga
Subject: A-500 rumors & comments
Message-ID: <8704240432.AA23509@cogsci.berkeley.edu>
Date: Thu, 23-Apr-87 23:32:21 EST
Article-I.D.: cogsci.8704240432.AA23509
Posted: Thu Apr 23 23:32:21 1987
Date-Received: Sat, 25-Apr-87 13:33:51 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 51
Keywords: A-500 autoconfig clocks


Rumors have it that the internal slot on the Amiga 500 will be able to accept
512 or so of SLOW FAST memory with no hope of splitting the bus to create
FAST FAST memory.  What does net-land think about this, and what does
Commodore have to say in it's defense?

#beginner_mode_on
For those who do not know, the Amiga custom chips can be programmed to do
operations like line draw and area fill in CHIP memory.  Programs can also
specify that extra colors are to be available on each video line.
Both of these things can use memory slots that would otherwise be available
for the processor.  This is a ->feature<-.  It is also a ->feature<- that
(on the Amiga 1000) there is a separate bus that the processor can have all
to itself.  Memory that attaches here is called FAST memory.
#beginner_mode_off

The slot on the 500 will have the disadvantage of contention with with the
bus used by the custom chips, yet not the advantage of being addressable
by them.  The real crime is that this memory will ->pretend<- to be FAST,
but actually be CHIP, well not really 'cause...

The hassles are potentially gigantic.  The drop in potential is tragic,
particularly for things like CAD that can be calculating in the background
while the blitter is off doing it's thing.

I feel the descision is unwise.  I am aware of the cost related reasons
(Hi Jeff!) for the descision.  Still, I don't think any of the third party
developers want to need to deal with SLOW FAST ram.

In decreasing order of expense to produce the base machine I offer the
following solutions:

1> Turn this into real FAST memory, buffered and isolated from CHIP memory.
2> Make this CHIP memory and poke a couple of holes in one of the ladies :-)
   to address it.
3> Since this is an EXPANSION board shuffle the cost of implementing item #1
   onto the board.  This is probably the best compromise of the three.
   Another point to consider is that this board will probably be cloned
   right off, as the internal 256k was.  Commodore can make a half-hearted
   and possibly profitless attempt at the board, and leave it to the cloners
   to pull up the slack.

  ----------
  One more A-500 comment:  A clock chip on the above mentioned board is to be
  located at $dc00000 absolute with a reader on WB.  This is is AGE OF
  AUTOCONFIG, the DECADE OF 'PLUG AND PLAY'.  Cleaner for everybody except
  the poor sop who gets to design it would be a ROM that copies itself to
  RAM at config time and gets executed once DOS is up.  It can then stay
  resident (say, for a SCSI driver) or de-allocate itself (our clock).
  ----------
  -Bryce-