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From: cmcmanis@sun.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: expanding amiga 1000 to 2000
Message-ID: <13509@sun.uucp>
Date: Tue, 17-Feb-87 20:11:30 EST
Article-I.D.: sun.13509
Posted: Tue Feb 17 20:11:30 1987
Date-Received: Thu, 19-Feb-87 06:07:18 EST
References: <12279780357.24.PKG.SPARKMAN@MCC.COM>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 51
Summary: Try again

In article <12279780357.24.PKG.SPARKMAN@MCC.COM>, PKG.SPARKMAN@MCC.COM (Aubrey Sparkman) writes:
> Please don't give up on pressing for answers about modifing your amiga 1000.
> You aren't being thick headed, others simply aren't listening (reading
> properly).   I thought of the above expansions myself and hoped it would be
> discussed.

Actually the schematics are really useful for trying to figure out what 
you can and cannot do with the Amiga internals. Easily worth the $20
Commodore is charging for them (they also include PAL codes). Basically,
it isn't fruitful discussing expanding the 'chip' ram of the Amiga if
one has no idea what the new chips will look like. As for adding internal
memory that looks like 'fast' ram that is possible and documented in the
latest RoboCity News (the FAUG newsletter) and in Amazing Computing I
believe. 

> As far as the power requirements goes, it seems that one could (In line with
> the daughter board idea) remove the 256K plug in module from the front of
> the amiga 1000, remove the 256K dram chips from the mother board, and use
> 1 meg dram chips to get 2 meg chip ram without changeing chip count.
> Yes I know the 1 meg chips are more expensive, but then you don't have to add
> a power supply (do you?) and it is simpler.

Two problems here (certainly not fatal however) first there are only 18
address lines on the nose piece so you would have to put a couple of 
wires through the front, secondly if you replaced the 256K chips with
1Meg chips you would have 1 Meg. Now if you remove the nosepiece and 
replace the internal 256K chips with 1Meg chips (and add a couple of
wires) you could have a 1 meg internal Amiga. And the power requirements
would be relatively straight forward since replacing 512K of 256K rams
(the nosepiece and the internal ram) with 1Meg of 1Meg chips is a net
reduction in power required. 
 
> So lets investigate (or explain why not) this daughter board for one meg chips
> agnes, paula, and any other sisters I forgot to mention.
> Aubrey Sparkman

As mentioned by others (including Commodore's engineering staff) you cannot
increase the address space of the custom chips. You can add internal RAM
expansions however the new memory would have to be allocated to the 'fast'
RAM pool rather than the Chip ram pool. The only difficulties you will
encounter will be the power requirements (avoidable with good planning),
fitting the darn thing in there (have you taken off the lid to your Amiga?),
and making sure the new memory resides in a compatible address space. 
Note that this is also true of the Amiga 2000 because it uses the same
custom chips as the Amiga 1000 and they are limited to accessing 512K
of 'Chip' ram.

-- 
--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.