The 3Com EtherLink III 3C509B-TPO is family of the EtherLink III network cards of 3Com. This version is a 16 bit ISA card with RJ-45 UTP connector.
The settings shown via 3C5X9CFG.exe on the bridgeboard.
I prefer to change the transceiver type to RJ-45 and optimization DOS Client. Full Duplex had no major effect on the performance.
TcpSpeed shows 261 kB/s with half duplex and 269 kB/s with full duplex.
I use RoadShow TCP/IP for my Amigas.