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From: vishniac@wanginst.UUCP (Ephraim Vishniac)
Newsgroups: net.micro.mac
Subject: Re: Re: 1.5 Meg Upgrade from MacMemory
Message-ID: <1212@wanginst.UUCP>
Date: Wed, 16-Oct-85 08:49:55 EDT
Article-I.D.: wanginst.1212
Posted: Wed Oct 16 08:49:55 1985
Date-Received: Thu, 17-Oct-85 20:30:07 EDT
References: <465@spice.cs.cmu.edu.ARPA>
Organization: Wang Institute, Tyngsboro, Ma.  01879
Lines: 22

> In one of the MAUG conferences, Andy Hertzfield said that it was important
> for people upgrading to more than 512K of memory to get upgrades that placed
> the screen at the top of memory.  Currently, locating screen memory at the
> top of a >512K Mac requires patching the ROMs to set ScreenBase correctly.
> The new Apple ROMs should set ScreenBase correctly (= pointing to the top
> of memory) for Macs with more than 512K of memory.  But the new ROMs won't
> help you (and in fact will hurt you) if you have a >512K upgrade that leaves
> the screen at the top of the first 512K of memory.
> 
> I called MassTech about their upgrades, and it sounds like they're doing
> things right (the extra memory is contiguous with the standard memory, the
> screen is located at the top of the address space, and the board contains
> patches to the current ROM to let it know about the extra memory)...
> 
Another point about the MassTech upgrade.  The ROM patches are contained in
an additional ROM.  The board is designed so that with the patch ROM absent,
the native ROMs are unaffected.  So, when the new Apple ROMs are available,
just install the new ROMs, pluck out the patch ROM, and you're in business.
-- 
Ephraim Vishniac
  [apollo, bbncca, cadmus, decvax, harvard, linus, masscomp]!wanginst!vishniac
  vishniac%Wang-Inst@Csnet-Relay