sys/mdec/httoggle.s

/*
 * Prototype toggle in bootstrap code for ht type tapes.
 * If on anything but a 780 with a tape at slave 1 of mba 1
 * this will have to be repaired by patching mba and ht.
 */
        movl    mba,r10
        mull3   ht,$0x80,r11
        addl3   r11,r10,r11
        addl2   $0x400,r11
        movl    $1,4(r10)
        movl    $9,(r11)
        cvtwl   $012300,0x24(r11)
        clrl    12(r10)
        movl    $0x80000000,0x800(r10)
        cvtwl   $-512,16(r10)
        movl    $0x39,(r11)
        halt
        .align  2
mba:    .long   0x20012000
ht:     .long   0