I've got a NetBSD (1.2 beta, july 19th) box w/two 3c509's.  Sometimes 
when I boot, the boards are not always detected in the same order - ep0
becomes ep1 and ep1 becomes ep0 as the following lines saved by
syslog show:

Aug  6 00:20:45 ... : ep0 at isa0 port 0x300-0x30f irq 3: 3Com 3C509 Ethernet
Aug  6 00:20:45 ... : ep0: aui/bnc/utp address 00:a0:24:0f:12:05
Aug  6 00:20:45 ... : ep1 at isa0 port 0x310-0x31f irq 10: 3Com 3C509 Ethernet
Aug  6 00:20:46 ... : ep1: aui/bnc/utp address 00:20:af:bf:be:a9
------------------------------------------------------------------------------
Aug  6 00:28:11 ... : ep0 at isa0 port 0x310-0x31f irq 10: 3Com 3C509 Ethernet
Aug  6 00:28:11 ... : ep0: aui/bnc/utp address 00:20:af:bf:be:a9
Aug  6 00:28:11 ... : ep1 at isa0 port 0x300-0x30f irq 3: 3Com 3C509 Ethernet
Aug  6 00:28:11 ... : ep1: aui/bnc/utp address 00:a0:24:0f:12:05

This switch usually happens after I've run the DOS config utility (3c5x9cfg).

Ideas?

Josh