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From: lbl@druhi.UUCP (LocklearLB)
Newsgroups: net.micro.atari
Subject: Re: Serious ST Questions
Message-ID: <128@druhi.UUCP>
Date: Wed, 19-Feb-86 11:39:49 EST
Article-I.D.: druhi.128
Posted: Wed Feb 19 11:39:49 1986
Date-Received: Thu, 20-Feb-86 07:45:45 EST
References: <708@ihwpt.UUCP>
Distribution: net
Organization: AT&T Information System Labs, Denver, Co
Lines: 74
Summary: clarifications and answers to some of the questions

> First, I'd like to know how many chips in the ST are
> soldered in instead of socketed, and which these are.
> Please answer this for the early STs, the current models,
> and the future shipments.  I'd like to decide which
> vintage model would be best for doing hardware upgrades
> (piggy back RAM, 68010, etc).

In the revision B board, all of the chips are soldered except for the 
custom chips (Memory Manager, Glue, Video).  This probably will not
change in the future, except that the custom chips might also get 
soldered in also.
I have done the ram upgrade on my board with no problems.  I have also
talked with several people who have done the upgrade on newer machines
with no problem.  Get the latest vintage machine you can.

> 
> More serious:  How can the ST be bus-expanded?
> The *other* brand brings its entire bus to the side connector,
> but the ST has only a read-only 128K game cart socket
> (what, games?  on an Atari??).  How can there be an
> expansion chassis into which we can plug boards with
> lotsa RAM, 32000 co-procs, or whatever else needs some
> direct bus access?  Will we be stuck with a box hung
> off the floppy or hard disk serial ports?
> Which can't be accessed directly?
> Tecmar is already advertising a true expansion box
> for the you-know-what.

The floppy disk and hard disk ports are parallel ports, NOT serial ports.
The hard disk port is really a general purpose DMA port for the Atari.
This port, with some massaging, can be made to look like a SASI or SCSI port.
This, of course, takes a little extra hardware on a PC board.  The Atari
hard disk is a disk connected to the extra hardware which is
then connected to the Atari.  The hard disk thinks it is talking SASI (or
SCSI, I can't remember at the moment).  Presumably, one could build an
expansion cabinet using this method of communicating.  It isn't as good
as a full bus expander, but it can be very useful.
> 
> Finally:  Is it possible to write directly to the graphics
> bitmap in RAM (from an assembler or C program)?
> Where speed is of the utmost, we'll need to be able
> to do our own custom bit-blits, quickdraws, etc.
> to compete with the custom graphics chips in the
> high-priced machine.
> I heard that on one of the machines (forget which)
> you were somehow prevented from direct access to the
> graphics area (this may just be a BASIC restriction,
> as there is no MMU in either machine to stop machine
> code routines from doing it).
> 
There IS a primitive MMU in the Atari that will prevent access to certain
areas of memory if you are not executing in 'supervisor' mode.  And yes, it
is possible to write directly to the bitmap RAM.  You won't need to write your
own bit-blits, quickdraws, etc. because they are already provided in the
line-A interface in the ROM of the Atari.  This code is what the low-level
routines in GEM and VDI end up calling.  If you wish to bypass GEM to get
ultimate speed, all you need to do is use these routines.  
> Hoping to get an ST soon, mike k

I hope you do too.  Order a development kit also,  it will be worth the time
it takes to delve through all of the crud to get the juicy parts.  Atari and
Digital Research are introducing a new version of the kit within a month that
is supposed to have many bug fixes and a total (and much needed!)
reorganization of the documentation.  You should probably wait until that
comes out to buy one.

Good Luck.

Barry Locklear
AT&T Information Systems Labs
Denver, CO
(303) 538-4954
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