HelenOS sources

DP_MAR0           322 uspace/drv/nic/ne2k/dp8390.c 	pio_write_8(ne2k->port + DP_MAR0, 0);
DP_MAR0           660 uspace/drv/nic/ne2k/dp8390.c 	pio_write_8(ne2k->port + DP_MAR0, (uint8_t) hash);
HelenOS homepage, sources at GitHub