G3 Minitower doesn't like 128mb and larger Memory

Discussion in 'Apple Collectors' started by bunnspecial, Mar 23, 2015.

  1. bunnspecial macrumors 603

    bunnspecial

    Joined:
    May 3, 2014
    Location:
    Kentucky
    #1
    I have two G3 desktops, and both are maxed out with low-density(and low profile) 256mb PC-133 RAM for a total of 768mb.

    I recently acquired a pair of Minitowers-one a regular, and the other a server. I haven't changed the memory out in the server(I've focused more on getting the hard drives set up how I wanted) but have been playing some with the RAM in the other minitower.

    The previous owner had a installed 3x64mb high density PC-100 modules, and the computer works fine with these.

    I went through my memory drawer, and initially started trying to install a single PC-133 256mb low density module in place of one of the 64mb. It would chime, but would not boot. I then switched over to low density PC-133 128mb sticks(I have a TON of these), and it still wouldn't boot. I'll also add that I was careful to only use non-ECC memory. The only way I can get it to boot is with the 64mb modules.

    Any ideas about what could be going here? Am I just going to have to live with this computer having 192mb of RAM?
     
  2. MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #2
    It's possible the SPD on the modules don't have a specification for 100Mhz.

    I can only suggest ensuring the edge fingers are clean and trying "DIMM First Aid" under native OS 9.

    http://www.macupdate.com/app/mac/5714/dimm-first-aid

    Failing that, TechTool Pro v3.0.9 might be able to give you more info on what is installed.

    Try one of the 64MB DIMMs along with one of the 128MB to see if System Profiler can see what they are.
     
  3. bunnspecial thread starter macrumors 603

    bunnspecial

    Joined:
    May 3, 2014
    Location:
    Kentucky
    #3
    Thanks for the program suggestions.

    With that said, I may not have made myself completely clear. Even if I only install a single 128mb and leave the other two 64s in place, it still won't boot.

    At least one of the 64s currently installed is PC-133, so I don't think it's a timing issue.
     
  4. MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #4
    Make sure the 64MB DIMMs are in the lower banks. That is Bank0 and Bank1. Put the 128MB DIMM in Bank2

    Also, the timing isn't necessarily the problem, but the SPD on the DIMM needs to provide timing data for it to work at a lower speed. If the DIMM is sold as a PC133, it may not have timing data for PC100, or 66. The motherboard then refuses to use it.
     
  5. havokalien macrumors 6502a

    havokalien

    Joined:
    Apr 27, 2006
    Location:
    Kelso, Wa
    #5
    same issue in cube

    My cube does the same thing and he is correct about the backwards compatibility. PC133 won't always work in a PC100 Mac.
     
  6. jruschme macrumors 6502

    jruschme

    Joined:
    Dec 20, 2011
    Location:
    Brick, NJ
  7. bunnspecial thread starter macrumors 603

    bunnspecial

    Joined:
    May 3, 2014
    Location:
    Kentucky
    #7
    Unfortunately, utilities like that won't help me when the computer won't even boot!
     

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