Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!ucla-cs!zen!hoser.berkeley.edu!bryce
From: bryce@hoser.berkeley.edu.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: What's in a name (and who is "Fang")?
Message-ID: <3932@zen.berkeley.edu>
Date: Thu, 24-Sep-87 03:41:29 EDT
Article-I.D.: zen.3932
Posted: Thu Sep 24 03:41:29 1987
Date-Received: Sat, 26-Sep-87 09:57:00 EDT
References: <14218@amdahl.amdahl.com> <2336@cbmvax.UUCP> <14580@amdahl.amdahl.com> <277@uscacsc.UUCP>
Sender: news@zen.berkeley.edu
Reply-To: bryce@hoser.berkeley.edu.UUCP (Bryce Nesbitt)
Organization: Center Tapped Solids, Inc.
Lines: 35
Keywords: jumpers for 1 Meg of CHIP ram

In article <277@uscacsc.UUCP> papa@pollux.UUCP (Marco Papa) writes:
>The following are excerpts from the "Commodore Amiga A500/A2000 Techical 
>Reference Manual":

>[One] jumper determines the high-order address bit for Fat Agnus (Fang). In its
>normal position, the high order bit is A23; in its other position, this
>bit is A19.  The current Fat Agnus chip requires the A23 signal for proper 
>management of the memory at $C00000 [hint, hint!]. Future Fat Agnus chips
>may map things differently."

[One] on the A500 this is JP3.  To move the RAM you also need to disable the
_exram signal into Gary.  This is pulled low if there is ram at $C00000,
but needs to float high if you move it to $080000.  The input connects
pin 32 of the memory connector, or you can lift out Gary and bend
Gary pin 32 out.  (Neat! same pin on the Gary and memory connector)

The memory goes to $080000 and configures as 1 megabyte of chip ram.
You can't actually use the machine like this; it will crash as soon
as any memory is allocated as chip from the area above $07ffff.

Those peope who added the internal 512K memory hacks that showed
up at $080000 have the same problem under Kickstart V1.2.  They run a
program that claims to reoder things to work.  The versions I have seen don't.
When memory is tight the last few memory allocations get screwed and things
crash.  (I don't have one of these myself)

If you have one of those internal half-fast ram hacks, the solution
is to add David Haynie's "AUTOMEG" modification.  This brings that
memory back into the autoconfiguration scheme. 

 
|\ /|  . Ack! (NAK, ENQ, SYN)
{o O} . 
 (") 	bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce
  U	How can you go back if you have not yet gone forth?