It's the CPU, 060 is highly recommended for good performance with PCMCIA NICs.
With 060 I could reach 786KB/s (the other end was just silly P120 laptop). A friend could reach 819KB/s. Both with 10mbit cards.
These are real-world ftp transfer speeds, not some imaginary theoretical values.
Unfortunately I no longer have the Amiga built up, so I can't test my 100mbit PCMCIA NIC in real 100mbit network. I wouldn't expect much over 1MB/s speed, however.
