Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!rutgers!uwvax!puff!uhura!captain
From: captain@uhura.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: 2 meg chip ram
Message-ID: <117@uhura.UUCP>
Date: Thu, 5-Feb-87 12:35:20 EST
Article-I.D.: uhura.117
Posted: Thu Feb  5 12:35:20 1987
Date-Received: Sat, 7-Feb-87 12:28:52 EST
References: <2438@jade.BERKELEY.EDU>
Organization: Undergraduate Project Lab @ UW-Madison
Lines: 54
Summary: Sounds scary to me...

In article <2438@jade.BERKELEY.EDU>, spencer@eris.BERKELEY.EDU (Randy Spencer) 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?  

No. No. No. He would NOT have chip mem. If he failed to take the adress line
over from the fast mem bus he would have unadressable memory.

What your friend has done is a common hack currently. He has piggybacked
another 512k of memory on top of his chip mem. He then takes one address
line over from the expansion bus in order to map the memory into a
different bank than the chip mem. What he has now is memory which the
computer THINKS is fast memoru, but in fact has all the arbitration
slow downs of chip memory.

The command he is executing in software is an ADDMEM. He has to do this because
etra memory (i.e. fast mem) is supposed to call out on the bus during 
startup as to how much and where it is. (This is part of the Amiga's
autoconfigure, this frees you up from the limitations imposed by a system
like the IBM-PC where you have to set dip switches internally). If he
failed to do this he would NOT have chip mem there, he would have inacessable
memory.

In addition, all the Amiga ports are rated for power output in the hardware
manual. Developers are assured that they can pull the rated power from
the various ports' power pins. Concievably, if you had a system with a mumber ofperipherals, you could experience REAL problems with the extra power you are
stealing from inside the machine. (Also, this hack requires you to 
solder directly to memory chips... yuk!)

In conclusion. If you don't mind soldering to chips, your new memory being
slow, still being restricted to 512k chip memory (the bus in the a100 has
NO more room, so forget about expanding that), possibly pushing the limits
of your power supply, and scaring any reasonable maintainence facillity
from ever touching your machine again (it will be VERY non-standard), go
ahead and do the hack. It is certainly cheaper.

Myself, I paid $1500 for my Amiga, I can't afford NOT to spend the extra
money to do it right!

Jeff Kesselman
captain@uhura

Disclaimer: These ideas are mostly mine, though I hang about with some bright
people and steal their's occasionally.

>