This question is not related to U-boot(reset) in perticular but the 440GX. I did not get a response that answer my question from IBM or AMCC.

In the 440GX PCI registers at offset 0xd4, there is the power managemement register. if you write 3 then 0 it should reset the 440GX. However, once Linux or U-boot are booted, this does not work anymore. I have not found what prevent the reset.

If you have any clue, please let me know.