Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!zaphod.mps.ohio-state.edu!mips!bridge2!3comvax!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Bridgeboards taking 2M of autoconfig space
Summary: AmigaDOS allocates 2M minimum with current memory boards.
Message-ID: <946@tardis.Tymnet.COM>
Date: 26 Feb 90 09:39:37 GMT
References: <1827@esunix.UUCP>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: BT Tymnet, San Jose, CA
Lines: 22

In article <1827@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes:
>I don't own a Bridgeboard, but may need to get one in the future. I've
>heard that they take 2M out of the autoconfig space.
>Isn't the shared RAM only 128K? And doesn't the autoconfig protocol
>provide for a minimum size of 64K? Unless there is something I'm missing
>(quite likely), the Bridgeboards should only take 128K, not 2M.

The problem appears to be in that current memory expansion boards are
2M, 4M, or 8M, and must start on a 2M boundary.  Which means that the smallest
chunk of autoconfig addresses that can be allocated to a given board is
2M.  When the Bridge Board gets 128K, the remaining 1920K is unusable.

Too bad there isn't a way to make an Amiga memory board appear to the system
as 3/4, 7/8, or 15/16 of its full size, so that the rest of the address
space can be allocated to something else.  (DEC did that with their smaller
PDP-11 systems for years.)

-- 
Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com
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