Maybe just one of the voltages (possibly 3.3v) is down, or at least below spec.
Could be that your old PII board doesn't care about that voltage but your new board does. I'm guessing that your old board uses 72-pin dimms for memory. As far as I know those run on 5v. The PII core voltage is probably also derived from 5v, in which case the 3.3v line would be redundant on that board.
Your new board will almost certainly use the 3.3v for processor core voltage, and maybe for memory voltage too.
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