How about testing the existing parts to make sure they can negociate properly to 100MB when connected to a GigE?
The MCF52236AF50A does not appear to do it properly.
We do test the chips in GigE routers.
Unfortunately, this chip's part number was left out of the errata, but it is in the same family and suffers the same bug.
Look at this errata: MCF52236 Errata
Look at errata #10 and see if that helps.
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