quote from http://www.cs.usfca.edu/~cruse/cs326/RTL8139_ProgrammersGuide.pdf

"Early Tx Threshold: Specifies the threshold level in the Tx FIFO to
begin the transmission. When the byte count of the data in the Tx FIFO
reaches this level, (or the FIFO contains at least one complete packet) the
RTL8139(A/B) will transmit this packet.
000000 = 8 bytes
These fields count from 000001 to 111111 in unit of 32 bytes.
This threshold must be avoided from exceeding 2K byte."

try lowering the value and also try increase it, i dont think you will notice any speed increasing, but it might speed up browsing

VanBuren