problem with dm9000 in 531

hi all:

dm9000 driver is ok in blackfin 533,but it doesnt work well in 531.(not modified from 533),at first ,i cannt ping host ,for example ,the ip of board is 192.168.2.253,then in the board i ping 192.168.2.99,but it does not work.

later i change

int_status = ior(db, DM9000_ISR); /* Got ISR */

iow(db, DM9000_ISR,int_status);

into

int_status = ior(db, DM9000_ISR); /* Got ISR */

iow(db, DM9000_ISR,0x00);

now i can ping 192.168.2.99,but response time is too long :

PING 192.168.2.99 (192.168.2.99): 56 data bytes

84 bytes from 192.168.2.99: icmp_seq=0 ttl=64 time=1007.5 ms

84 bytes from 192.168.2.99: icmp_seq=1 ttl=64 time=1006.2 ms

84 bytes from 192.168.2.99: icmp_seq=2 ttl=64 time=1006.2 ms

84 bytes from 192.168.2.99: icmp_seq=3 ttl=64 time=1006.3 ms

84 bytes from 192.168.2.99: icmp_seq=4 ttl=64 time=1006.2 ms

84 bytes from 192.168.2.99: icmp_seq=5 ttl=64 time=1007.6 ms

if i ping the board(ping 192.168.2.253) this time from another PC,then response is short:

PING 192.168.2.99 (192.168.2.99): 56 data bytes

84 bytes from 192.168.2.99: icmp_seq=0 ttl=64 time=1006.9 ms

84 bytes from 192.168.2.99: icmp_seq=1 ttl=64 time=1007.1 ms

84 bytes from 192.168.2.99: icmp_seq=2 ttl=64 time=1007.7 ms

84 bytes from 192.168.2.99: icmp_seq=3 ttl=64 time=6.0 ms

84 bytes from 192.168.2.99: icmp_seq=4 ttl=64 time=1007.7 ms

84 bytes from 192.168.2.99: icmp_seq=5 ttl=64 time=6.0 ms

84 bytes from 192.168.2.99: icmp_seq=6 ttl=64 time=3.9 ms

84 bytes from 192.168.2.99: icmp_seq=7 ttl=64 time=3.7 ms

84 bytes from 192.168.2.99: icmp_seq=8 ttl=64 time=1007.7 ms

84 bytes from 192.168.2.99: icmp_seq=9 ttl=64 time=6.0 ms

84 bytes from 192.168.2.99: icmp_seq=10 ttl=64 time=3.7 ms

84 bytes from 192.168.2.99: icmp_seq=11 ttl=64 time=3.9 ms

84 bytes from 192.168.2.99: icmp_seq=12 ttl=64 time=3.9 ms

84 bytes from 192.168.2.99: icmp_seq=13 ttl=64 time=3.8 ms

84 bytes from 192.168.2.99: icmp_seq=14 ttl=64 time=4.5 ms

--- 192.168.2.99 ping statistics ---

15 packets transmitted, 15 packets received, 0% packet loss

round-trip min/avg/max = 3.7/338.8/1007.7 ms

i ask for help

thanks