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From: kanefsky@cs.umn.edu (Steve Kanefsky)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Missing IIsi ROM SIMM ???
Message-ID: <1990Dec21.205235.7618@cs.umn.edu>
Date: 21 Dec 90 20:52:35 GMT
References: <3624@uakari.primate.wisc.edu>
Organization: University of Minnesota, Minneapolis - CSCI Dept.
Lines: 32

In article <3624@uakari.primate.wisc.edu> bin@primate.wisc.edu (Brain in Neutral) writes:
>Well, I'll freely confess to not having any knowledge of hardware, but...
>
>I just installed 4MB memory in two Macintosh IIsi's, which were
>ordered in identical configuration but which arrived about 3 weeks
>apart.  (Memory was from Chip Merchant, by the way.  Installation
>was a snap.  Memory worked perfectly).
>
>I noticed that the second machine didn't have the card installed that
>sits next to the RAM SIMM slots.  "Odd, I thought.  What is it?" and
>peered closer to the circuit board.  It says "ROM SIMM" by the card
>bay.
>
>So I have two "identical" machines, except that one is apparently
>missing its ROM!  But it works...
>
>What's the deal?

The ROM SIMM slot was intended for ROM *upgrades*.  The ROM included with
newer IIsi's is soldered onto the motherboard (to save on manufacturing costs).

Apple did mention that some of the first IIsi and LC Macs may have the ROM
on SIMMS instead of soldered in. 

It shouldn't make any difference at all in terms of performance or 
upgradability whether your ROMs are soldered-on or on SIMMS.  It just saves
apple a few $$$ to mass-produce mother boards with the ROM soldered-on.


-- 
Steve Kanefsky             
kanefsky@cs.umn.edu