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From: peck@ral.rpi.edu (Joseph Peck)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: What Happens If You Have > 9 Meg??
Message-ID: <=S4^VX|@rpi.edu>
Date: 18 Jan 91 18:14:24 GMT
References: <7017@crash.cts.com>
Organization: Rensselaer Polytechnic Institute, Troy NY
Lines: 57
Nntp-Posting-Host: ral.rpi.edu

In article <7017@crash.cts.com> lkoop@pnet01.cts.com (Lamonte Koop) writes:
>peck@ral.rpi.edu (Joseph Peck) writes:
>>In article <744@cbmger.UUCP> peterk@cbmger.UUCP (Peter Kittel GERMANY) writes:
>>>In article <6931@crash.cts.com> lgreen@pnet01.cts.com (Lawrence Greenwald) writes:
>>>>What would happen? Machine refuse to boot? Software go crazy?
>>>
>>>Everytime the last card in the row would refuse to autoconfig.
>>>Its memory simply wouldn't show up. For Autoconfiguration,
>>>the system only has the 8 MB pool of address space and when a
>>>certain board doesn't fit into this space or its remainder then
>>>it will not get activated.
>>
>>True enough for case 1, but for case 2 isn't the 4meg memory on the
>>card in the CPU slot?  Since I am 99.9999% sure of this (okay Dave,
>>make me look silly now :), the only intelligent place to place
>>this memory in the address space is outside of the 16meg limit of
>>the 68000.  This is especially true since I vaguely remember Dave
>>mentioning that there are sufficient address lines for up to 64meg
>>of 32 bit ram..... 
>
>I think you are confusing the difference between limitations of the CPU
>addressing space, and limitations imposed by AmigaOS.  AmigaOS limits
>AutoConfig memory to 9.5 megs (v1.3).  Additional memory can be added, but a
>board must be set up in a way as to be put in the system memory pool in a
>specific, unused place.  [The OS must also be "informed" that it is there as
>well].  The memory on the A2630 is AutoConfig, and therefore is tallied as
>part of the AutoConfig total limit.

No, I wasn't confusing the address space limitations, I just assumed that
I wasn't confusing anyone else.  Since Dr. Kittel already pointed out
that the 4 meg of 32 bit ram IS autoconfiguring, my statement about
the 13meg configuration being okay is out the door though.....  

Anyhow, what I meant by there being insufficient address lines was that
Commodore specifications for the 68000 based amiga's included only
8 megabytes of autoconfiguring space.  All other areas are basically 
considered "offlimits" for user type add on's.  So even though there
are holes in the 68000 addressing space outside of the autoconfiguring
area, later versions of the custom chips may use those addresses.
So in order to be safe, you shouldn't put things where they don't
belong.

I do realize that you CAN put things in those holes.  In fact, I was 
considering putting my own register in to provide software control
for a 7/14Mhz accelerator that I worked on a while ago.  I decided
not to because A) My hack is designed for a 500 or 2000, I happen
to own a 1000.  B) I am finishing a commercial game that will
(hopefully) earn me some money, while making a nice hack won't at the
moment.  C) School inevitably tries to occupy every spare (and 
not so spare) moment that I have.....

>
>                             LaMonte Koop

Joe

peck@ral.rpi.edu