white screen when booting 9.1 on quadra 700

hello,

i have a macintosh quadra 700, and have been attempting to install netbsd on it. i have tried both the 9.1 kernel and a nightly head build.

when i boot the installation kernel from the booter application, i am shown a white screen, and my computer proceeds to do absolutely nothing no matter how long i wait. if i press the interrupt button, i am dropped into the debugger, but cannot interact with it. the same is true both over graphical and serial console.

across multiple boot attempts, if i press the interrupt button, the debugger always seems to stop in the exact same place, varying only when i change the kernel version. for the released 9.1 kernel, it is as follows:

    [   1.0000000] Panic switch: PC is 0x1c32c.                                  
    Stopped in pid 0.1 (system) at  29eb8:  unlk    a6                           
    db>            

does anyone have advice for troubleshooting this issue?