stevena1
Level 1 (20 points)

Q: ROM SIMM Slot - what's the purpose?

I had a few SIMMs laying around, and wanted to expand my Color Classic memory. I tried to see if it would read it and I got the preemptive Chimes of Doom (No Sad Mac) with a grey screen. I opened up to see the logic board recently to replace the clock battery to see a slot called "ROM SIMM". Same slot I have seen on my IIsi.

 

What was it for? What's the benefits? Was this the appendix for the Mac (an unneeded component for a logic board?)

Color Classic, Other OS, System 7.5.1/4MB/40MB/68K CPU

Posted on Oct 30, 2013 8:10 PM

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stevena1

Q: ROM SIMM Slot - what's the purpose?

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  • by Jeff,

    Jeff Jeff Oct 30, 2013 9:23 PM in response to stevena1
    Level 6 (11,559 points)
    Oct 30, 2013 9:23 PM in response to stevena1

    ROM code contains hardware-specific instructions for the computer at startup.  While the motherboard typically has soldered ROM chip(s), the idea behind the unused slot was to enable future additions to the ROM code.  In the beige G3s, there were no soldered ROM chips on the motherboard — just a single ROM slot with card.  It turned out to be a good thing, because the first generation of motherboards shipped with a poorly-programmed ROM code (example: lack of master/slave support for dual drives).  There were two subsequent revisions to the ROM card that shipped with later models.  Because the card could be removed, many of us who owned first generation motherboards were able to replace/upgrade the ROM card and correct some of the earlier oversights.

  • by stevena1,

    stevena1 stevena1 Oct 31, 2013 6:55 AM in response to Jeff
    Level 1 (20 points)
    Oct 31, 2013 6:55 AM in response to Jeff

    what chips are on the board that appear to be removable?

     

    I thought those were the ROM chips.

     

    I did some searching and found a page that there was SIMM that contained a bootable ROM image that could be used to troubleshoot, primarlly for the IIsi. I found that page on my Mac, I'm on my PC right now, so I'll have to look at that link again and then post it.