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Path: utzoo!watmath!clyde!rutgers!cbmvax!grr
From: grr@cbmvax.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: 2 meg chip ram
Message-ID: <1375@cbmvax.cbmvax.cbm.UUCP>
Date: Mon, 9-Feb-87 01:56:01 EST
Article-I.D.: cbmvax.1375
Posted: Mon Feb  9 01:56:01 1987
Date-Received: Tue, 10-Feb-87 04:29:41 EST
References: <2438@jade.BERKELEY.EDU>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 40

In article <2438@jade.BERKELEY.EDU> spencer@eris.BERKELEY.EDU () writes:
>
>I have a question for the people at commodore.  I have a friend who has just
>upgraded his A1000 to 1 meg of internal ram, it is addressed as Chip ram and
>he has to do something special to make it called fast ram.  So the question is
>when I heared that 2 meg chips were coming out I asked and the story was that
>there was no upgrade path.  Then my friend does this and is talking about 
>adding a power supply to power the rest of the internal 2 meg chip ram, and 
>was going to install all 2 meg.  That means that if he doesn't do that trick 
>that makes the amiga address it as fast mem, he would have an amiga with
>2 meg of chip ram.  Now couldn't that work with the new chips?  What else do
>we need?  
>
>Randy Spencer P.O. Box 4542 Berkeley CA 94704 (415)284-4740 C#(415)283-5469

Well, there's chip memory, and chip memory.  The problem is that the custom
chips will only generate address for the first 512K of memory, being limited
to 9 multiplexed address lines (18 bits == 262144*2 byte/work).  The additional
memory uses the timing and control provided by Agnus, but is only accessable
from the processor side.

There is another fix out there that relocates the added memory to C000000
territory, where 1.2 will automatically recognize it and not try to use it
as chip memory.  This results in a sort of "slow fast ram" configuration,
but it works...

As to the external supply, no need as long as he remembers that there are only
so many amp's coming out of the supply, and if he wants to use more inside,
then he can't expect to get the maximum allocation out of all the external
ports.

The real problem with making any new custom chips that address more chip
memory is that there aren't enough pins on the 48-pin agnus chip to add
another address line!  So either a different package would be needed or
some kind of external logic would have to be tacked on - which would
realistically require a whole new PC board...
-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)