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Path: utzoo!utcsri!utai!utecfa!mugc
From: mugc@utecfa.UUCP (ModemUserGroupChairman)
Newsgroups: net.micro.atari16
Subject: Re: Power supply
Message-ID: <1838@utecfa.UUCP>
Date: Sun, 25-May-86 13:28:10 EDT
Article-I.D.: utecfa.1838
Posted: Sun May 25 13:28:10 1986
Date-Received: Sun, 25-May-86 18:49:32 EDT
References: <8605100658.AA12747@ucbvax.Berkeley.EDU> <3407@ukma.UUCP> <171@sage.cs.reading.Ac.Uk>
Organization: Engineering Computing Facility, University of Toronto
Lines: 40

gordon@sage.cs.reading.Ac.Uk (Simon Gordon) Writes:
 (in message dated: Fri, 16-May-86 19:57:21 EDT)


<> Some people seem to get their facts twisted.

<> There seem to be two problems
<> 1) Some of the older power supplies cannot supply enough power if you have
<> the extra 16 ram chips to give 1 meg ( my one is black with a lead out of
<> each end, ive been using it for a month since the 1 meg upgrade and rom upgrade
<> which i had done at the same time)
<> 2) With twice as many ram chips, the MMU must do extra work    holding the
<> inputs to the ram chips at their normal voltage. The resisters are therefore
<> pull ups and do this job instead.

<> Simon Gordon @ Sibly Hall Reading University UK



	Now from what I read, the resistors went in series between the
	MMU and the ram chip RAS and CAS lines. If so, how can they be pull-ups
	then?

	MMU ]----/\/\/\/\-----[41256 RAM chips
		   resistor

	is not the same as a pullup configuration:




				       ^ Vcc
				       |
				       |
				       <
				       >
				       <
				       |
				       | 
	MMU ]--------------------------+----[41256 RAM chips