G4 cube RAM into eMac

Discussion in 'NZ Computing' started by mark, Sep 17, 2008.

  1. mark

    mark Guest

    Plugging PC100 RAM into a PC133 eMac slot is going to cause no problems?

    Mark TIA
    mark, Sep 17, 2008
    #1
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  2. mark

    David Empson Guest

    mark <> wrote:

    > Plugging PC100 RAM into a PC133 eMac slot is going to cause no problems?


    If the memory really is PC-100, and its serial presence detect EEPROM
    says so, then an eMac which expects PC-133 will simply ignore the RAM.
    It won't damage anything to try it, but I doubt it will work.

    If the memory really is PC-133 but had been installed in the Cube and
    was working at the slower PC-100 speed, then it is more likely to work
    in the eMac.

    --
    David Empson
    David Empson, Sep 18, 2008
    #2
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  3. mark

    David Empson Guest

    David Empson <> wrote:

    > mark <> wrote:
    >
    > > Plugging PC100 RAM into a PC133 eMac slot is going to cause no problems?

    >
    > If the memory really is PC-100, and its serial presence detect EEPROM
    > says so, then an eMac which expects PC-133 will simply ignore the RAM.
    > It won't damage anything to try it, but I doubt it will work.
    >
    > If the memory really is PC-133 but had been installed in the Cube and
    > was working at the slower PC-100 speed, then it is more likely to work
    > in the eMac.


    A third possibility occurs to me: if the memory is really PC100 but its
    serial presence detect EEPROM has been programmed to lie and pretend it
    is PC133, and it really can't sustain that speed, then putting it in an
    eMac which expects PC133 will result in an extremely unreliable and
    crash-prone computer (but it still won't cause physical damage).

    The eMac cannot slow down its memory bus clock speed to work with PC100
    memory, but it can adapt to PC133 with varying number of wait states (as
    long as the memory is correctly programmed to report its
    characteristics), i.e. you can use PC133-222, PC133-322 or PC133-333. If
    the eMac has two modules with different wait states, it will operate at
    the specs of the slowest memory (more wait states).

    Macs in general require a correctly programmed serial presence detect
    EEPROM on the memory module. A cheap/generic module which is missing
    this component or which hasn't had it programmed correctly will not be
    recognised by the Mac.

    --
    David Empson
    David Empson, Sep 18, 2008
    #3
  4. mark

    mark Guest

    In article <>,
    mark <> wrote:

    > Plugging PC100 RAM into a PC133 eMac slot is going to cause no problems?
    >
    > Mark TIA


    2 of the RAM cards are marked PC100-332-620.
    Are these 2 safe?

    Mark
    mark, Sep 20, 2008
    #4
  5. mark

    David Empson Guest

    mark <> wrote:

    > In article <>,
    > mark <> wrote:
    >
    > > Plugging PC100 RAM into a PC133 eMac slot is going to cause no problems?
    > >
    > > Mark TIA

    >
    > 2 of the RAM cards are marked PC100-332-620.
    > Are these 2 safe?


    No, they won't work. PC100-333 is the slowest variant of PC100 (three
    wait states for all types of access). The eMac requires PC133.

    Depending on how the memory has been configured, the possible outcomes
    are the eMac not starting up at all, crashing or being generally
    unreliable, or simply ignoring the memory and refusing to use it.

    --
    David Empson
    David Empson, Sep 20, 2008
    #5
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