


      DDDDIIIISSSSCCCC((((7777))))                      ((((RRRRiiiiddddggggeeee))))                      DDDDIIIISSSSCCCC((((7777))))



      NNNNAAAAMMMMEEEE
           disc - disc device

      DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
           ////ddddeeeevvvv////ddddiiiisssscccc refers to the boot device.  The system
           automatically creates an entry called ////ddddeeeevvvv////ddddiiiisssscccc for the
           system boot device.

           ddddiiiisssscccc_c_u refers to a Ridge disc device.  By convention, _c is a
           controller number in the range 0..3, and _u is a unit number
           on the controller in the range 0..3.


      DDDDEEEEVVVVIIIICCCCEEEE CCCCOOOODDDDEEEE
                                    _b_l_o_c_k-_t_y_p_e _o_r  _s_t_a_n_d_a_r_d
           _d_e_v_i_c_e _t_y_p_e         _m_a_j_o_r     _m_i_n_o_r     _c_h_a_r_a_c_t_e_r-_t_y_p_e _f_i_l_e _n_a_m_e

           boot disc      8    0    block          /dev/disc
           (system makes this)

           Disc device         8    _U    block          /dev/disc_U
           (mknod(1) makes this)

           The minor number _U is derived from a combination of the
           binary bits that represent the controller number and the
           unit number.  It is calculated by:

                                    (binary
           _c_o_n_t_r_o_l_l_e_r*    _u_n_i_t _d_e_v_i_c_e-_n_a_m_e    _m_i_n_o_r)    _m_i_n_o_r
                0    0    /dev/disc00    00-00     0
                0    1    /dev/disc01    00-01     1
                0    2    /dev/disc02    00-10     2
                0    3    /dev/disc03    00-11     3
                1    0    /dev/disc10    01-00     4
                1    1    /dev/disc11    01-01     5
                1    2    /dev/disc12    01-10     6
                1    3    /dev/disc13    01-11     7

           By convention, controller 0 is the device with "2" encoded
           on its address DIP-switches.

           The boot disc can be determined by checking the major and
           minor numbers of ////ddddeeeevvvv////ddddiiiisssscccc.


      FFFFIIIILLLLEEEESSSS
           /dev/disc

           /dev/disc00 /dev/disc01 /dev/disc02 /dev/disc03

           /dev/disc10 /dev/disc11 /dev/disc12 /dev/disc13




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      DDDDIIIISSSSCCCC((((7777))))                      ((((RRRRiiiiddddggggeeee))))                      DDDDIIIISSSSCCCC((((7777))))























































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