Thanks for a lot of help.
I finally solved the problem just now.
Current NetBSD ineterrupt Mode was only for sandpoint X2.
I have sandpoint X3 board - mismatch occurred.
There was a switch named SW2 on sandpoint X3 board.
ILEGACY mode in SW2 is for sandpoint X2 interrupt mode.
Now, I'll preceed for diskless booting.
Thank you very much for helping me, and I'll ask more again.

Boo Geum Jung
Senior Member of Research Staff,
Real-Time OS Team,
Switching & Transmission Technology Laboratory, ETRI
161 Kajong-Dong, Yusong-Gu Taejon, Korea, 305-350
Tel:+82-42-860-5315 home:http://circle.etri.re.kr/~bgjung