You can always look at the output of
# modinfo forcedeth.ko
and see if the pci-id you want to support is in the list of supported
devices.
It's supported alright, and the module is being loaded.
The trouble appears to be that the chipset is showing up as an Ethernet
bridge rather than a network card - and the installer won't use that.
There's a bugzilla report at
https://bugzilla.redhat.com/show_bug.cgi?id=156688 which seems to describe
the problem exactly.
Unfortunately for me, my BIOS doesn't seem to have the workaround
mentioned in there. This might mean that RHEL4 will not install :-(
Ho hum...
Vic.