cisco 3620 + HDVt1 high cpu usage

All
I am using router 3620 16/64 and ios
IOS (tm) 3600 Software (C3620-J1S3-M), Version 12.2(15)T10,
T1 using ISDN 23B+D for voice pstn

I am runing it on internet, and use h323 with cisco gk,
however i found that the cpu utilization is very high,
5 call about 10%
15 call about 40%
20 call about 70%

i just apply fair queue on ethernet and ip qos dscp cs5 media
no cdp
but even i remove this 2 setting, the cpu usage still high.

what can i do??
is it normal?



CPU utilization for five seconds: 33%/27%; one minute: 33%; five minutes:
33%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
41 678652 389567 1742 2.12% 1.93% 1.85% 0 IP Input
3 464 157 2955 1.47% 0.35% 0.09% 66 Virtual Exec
115 196716 192845 1020 0.81% 0.63% 0.68% 0 VOIP_RTCP
129 438716 105372 4163 0.65% 1.19% 1.18% 0 CCH323_CT
111 216352 190316 1136 0.65% 0.62% 0.60% 0 VTSP
104 173536 26230 6615 0.16% 0.40% 0.41% 0 ISDN
100 70492 30257151 2 0.16% 0.16% 0.19% 0 SAA Event
Proces
138 117968 99218 1188 0.16% 0.25% 0.25% 0 ISDN L2
Process
109 17032 82176 207 0.08% 0.03% 0.00% 0 ISDN From
Driver
23 684 122071 5 0.08% 0.00% 0.00% 0 TTY
Background
102 620 122035 5 0.08% 0.00% 0.00% 0 trunk
conditioni
10 0 1 0 0.00% 0.00% 0.00% 0 OIR Handler
11 24 4073 5 0.00% 0.00% 0.00% 0 Environmental
mo
12 8500 11585 733 0.00% 0.00% 0.00% 0 ARP Input
13 128 6107 20 0.00% 0.00% 0.00% 0 HC Counter
Timer
14



4443333322222222222222222222222222222222222222222222233333
2226666688888666666666666666444442222244444888886666611111
100
90
80
70
60
50
40 ********
30 **************************** ***************
20 **********************************************************
10 **********************************************************
0....5....1....1....2....2....3....3....4....4....5....5....
0 5 0 5 0 5 0 5 0 5
CPU% per second (last 60 seconds)