HelenOS sources

DP_MAR1           323 uspace/drv/nic/ne2k/dp8390.c 	pio_write_8(ne2k->port + DP_MAR1, 0);
DP_MAR1           661 uspace/drv/nic/ne2k/dp8390.c 	pio_write_8(ne2k->port + DP_MAR1, (uint8_t) (hash >> 8));
HelenOS homepage, sources at GitHub