Path: utzoo!attcan!uunet!cs.utexas.edu!usc!wuarchive!psuvax1!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: 2090/st-506 revisited
Keywords: Thanks Dave!!
Message-ID: <15316@cbmvax.commodore.com>
Date: 22 Oct 90 17:10:37 GMT
References: <1990Oct18.035721.2305@cbnewsj.att.com> <525@cbmger.UUCP>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 42

In article <525@cbmger.UUCP> peterk@cbmger.UUCP (Peter Kittel GERMANY) writes:
>In article <1990Oct18.035721.2305@cbnewsj.att.com> paulm@cbnewsj.att.com (paul.j.maioriello) writes:

>There is also other software that can be saved by using NoFastMem.
>But in the A3000 you may lose quite an amount of memory through this.

However, there is absolutely no reason for other software to fail based on
the A3000's 32 bit memory.  The A2090 and similar devices are a rather
unique problem, in that CBM never gave any guidelines for handling this
potential hardware/software conflict.  In all software-only situations, it
is absolutely clear, and has been for some time, that only full 32 bit
addressing is permitted in Amiga programs.  

Anyone with a program that fails should actively seek upgrades (eg, bug fixes)
from the program distributer.  While it might be possible to make some kind of
band-aid for this, that's not a proper solution.  I would really like to see
the actual problem fixed.

>So, I can imagine a little utility software (or an addition to
>SetCPU, Dave?) that could do the following:
>Invoked after Autoconfig took place and BindDrivers, it looks which
>portions of the 32-bit Fast mem are already used and which portions
>of the lower 16 MB address area are still free. Then it uses the MMU
>to remap that rest of 32-bit-RAM downwards into the old 16 MB area.

You could do that to make software that violates 32 bit addressing rules work
on the 3000, within limits.  That's not going to help at all in addressing the
problems with hardware, which are the only things I really consider a valid
problem, since they weren't really worked out in the first place.  The 
Expansion library should have had some function call, maybe "AllocZ2DMAMem()"
or some such, that would be guaranteed to return memory that was DMAable by
a Zorro II card.  Though, according to Amiga specs, any memory that's mapped
into the 24 bit address space must be reachable by a Zorro II bus master, so
proper guidelines way back when would have been almost as useful as this
function.  This was just a problem no one fully considered.

>Best regards, Dr. Peter Kittel  // E-Mail to  \\  Only my personal opinions... 

-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
	Standing on the shoulders of giants leaves me cold	-REM