RX2(4)              UNIX Programmer's Manual               RX2(4)

NAME
     rx2 - RX211/RX02 floppy disk

DESCRIPTION
     Rx2? refers to an entire disk as a single sequentially
     addressed file.  The physical disk sector size is 128 bytes
     for single density and 256 bytes for double density.  The
     logical block size is 1024 bytes.  Each diskette has 250
     logical blocks in single density and 500 logical blocks in
     double density.  The standard device names begin with
     ``rx2'' followed by the drive number.

     The size and density of the disks are specified as follows:

          disk  minor device  unit  density
          rx20  0             0     single
          rx21  1             1     single
          rx22  2             0     double
          rx23  3             1     double

     The block files access the disk via the system's normal
     buffering mechanism and may be read and written without
     regard to physical disk records.  There is also a `raw'
     interface which provides for direct transmission between the
     disk and the user's read or write buffer.  A single read or
     write call results in exactly one I/O operation and there-
     fore raw I/O is considerably more efficient when many words
     are transmitted.  The names of the raw files conventionally
     begin with an extra `r.'

     In raw I/O counts should be a multiple of 512 bytes (a disk
     sector).  Likewise _l_s_e_e_k calls should specify a multiple of
     512 bytes.

FILES
     /dev/rx2[0-3]       block files
     /dev/rrx2[0-3]      raw files

SEE ALSO
     dvhp(4), hk(4), hp(4), hs(4), ml(4), rf(4), rk(4), rl(4),
     rm(4), rp(4), xp(4)

DIAGNOSTICS
     rx2%d: hard error bn %d cs2=%b er=%b.  An unrecoverable
     error occured during transfer of the specified sector of the
     specified disk partition.  The contents of the two error
     registers are also printed in octal and symbolically with
     bits decoded.  The error was either unrecoverable, or a
     large number of retry attempts could not recover the error.

BUGS
     In raw I/O _r_e_a_d and _w_r_i_t_e(2) truncate file offsets to 512-

Printed 8/1/83                                                  1

RX2(4)              UNIX Programmer's Manual               RX2(4)

     byte block boundaries, and _w_r_i_t_e scribbles on the tail of
     incomplete blocks.  Thus, in programs that are likely to
     access raw devices, _r_e_a_d, _w_r_i_t_e and _l_s_e_e_k(2) should always
     deal in 512-byte multiples.

     DEC-standard error logging should be supported.

     A program to analyze the logged error information (even in
     its present reduced form) is needed.

Printed 8/1/83                                                  2