Max RAM on a 12" Apple 166 Pentium card

Perhaps the answer is blindingly obvious but here goes:

Everywhere I look I see the reference to the maximum amount of RAM on these boards being 80meg (16 on the card plus a 64meg DIMM). When I look up RAM prices, however, I'm seeing that there are 128meg 168-pin 5-v FPM DIMMS available for around $20 or so. Is there a limitation of the PC compatibility cards that prevents them from addressing a 128meg DIMM?

Thanks.
Neal
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"Is Graham Chapman really dead or is he just being difficult?" - E. Idle