HelenOS sources

DP_MAR3           325 uspace/drv/nic/ne2k/dp8390.c 	pio_write_8(ne2k->port + DP_MAR3, 0);
DP_MAR3           663 uspace/drv/nic/ne2k/dp8390.c 	pio_write_8(ne2k->port + DP_MAR3, (uint8_t) (hash >> 24));
HelenOS homepage, sources at GitHub