2.11BSD#431 - /usr/man/cat4/rx.0

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


NAME
     rx - DEC RX02 floppy disk

SYNOPSIS
     /sys/conf/SYSTEM:
	  NRX  rx_units  # RX02

     /etc/dtab:
	  #Name Unit# Addr   Vector Br Handler(s)      # Comments
	  rx	?     177170 264    5  rxintr	       # rx02

     major device number(s):
	  raw: 17
	  block: 8
     minor device encoding:
	  bit 01 specifies drive: <rx_drive>
	  bit 02 specifies density: single: 0, double: 1

DESCRIPTION
     The rx device provides access to a DEC RX02 floppy disk unit
     with M8256 interface module (RX211 configuration). The RX02
     uses 8-inch, single-sided, soft-sectored floppy disks (with
     pre-formatted industry-standard headers) in either single or
     double density.

     Floppy disks handled by the RX02 contain 77 tracks, each
     with 26 sectors (for a total of 2,002 sectors).  The sector
     size is 128 bytes for single density, 256 bytes for double
     density.  Single density disks are compatible with the RX01
     floppy disk unit and with IBM 3740 Series Diskette 1 sys-
     tems.

     Files with minor device numbers 0 and 1 refer to drives 0
     and 1 in single density mode; minor devices 2 and 3 refer to
     drives 0 and 1 in double density mode.  The standard device
     names begin with ``rx'' followed by the drive number and
     then a letter a-b for single and double density access to
     the drive respectively.  The character ? stands here for a
     drive number in the range 0-1.

     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 the buffer must begin on a word (even) boundary,
     and counts should be a multiple of the disk's sector size


Printed 11/26/99	January 27, 1996			1


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


     (either 128 or 256 bytes depending on selected density.)
     Likewise seek calls should specify a multiple of the disk's
     sector size.

     In addition to normal (`block' and `raw') i/o, the driver
     supports formatting of disks for either density.

DISK SUPPORT
     The rx driver does not support pseudo-disks (partitions).
     Each file rx?[ab] refers to the entire drive 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 size and density of the disks are specified as follows:

	  disk	minor device  unit  density
	  rx0a	0	      0     single
	  rx1a	1	      1     single
	  rx0b	2	      0     double
	  rx1b	3	      1     double

     Even though the storage capacity on a floppy disk is quite
     small, it is possible to make file systems on them.  For
     example, the commands
	  % rxformat /dev/rrx0a
	  % newfs /dev/rrx0a
     and
	  % rxformat /dev/rrx1b
	  % newfs /dev/rrx1b
     format and make file systems on the single density disk in
     the left drive and the double density disk in the right
     drive with 241 and 486 kbytes available, respectively, for
     file storage.  Using tar(1) gives somewhat more efficient
     utilization of the available space for file storage.  The
     RX02 disks are primarily useful for small archives and
     transfer of small systems or distributions.

     An ioctl(2) call is available is available to format RX02
     disks:
	  #include <pdpuba/rxreg.h>
	  ioctl(fildes, RXIOC_FORMAT)
     The density is determined by the device opened.

FILES
     /dev/rx[01][ab]	 block files
     /dev/rrx[01][ab]	 raw files
     /dev/MAKEDEV	 script to create special files
     /dev/MAKEDEV.local  script to localize special files


Printed 11/26/99	January 27, 1996			2


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


SEE ALSO
     hk(4), ra(4), ram(4), rk(4), rl(4), rp(4), si(4), xp(4),
     dtab(5), autoconfig(8), rxformat(8V)

DIAGNOSTICS
     rx2%d: hard error sn%d cs=%b er=%b.  An unrecoverable error
     occurred during transfer of the specified sector of the
     specified disk.  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 read and write(2) truncate file offsets to disk
     sector size block boundaries (either 128 or 256 bytes
     depending on the selected density), and write scribbles on
     the tail of incomplete blocks.  Thus, in programs that are
     likely to access raw devices, read, write and lseek(2)
     should always deal in disk sector size multiples.

     DEC-standard error logging should be supported.

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

     The 4.3BSD rx driver which supports more capabilities should
     be ported to 2.11BSD.


Printed 11/26/99	January 27, 1996			3