BR(4)							     Kernel Interfaces Manual							     BR(4)

NAME

       br - EATON BR1537/BR1711 1538[A,B,C,D] moving head disk

SYNOPSIS

       /sys/conf/SYSTEM:
	    NBR  br_drives # EATON 1537/1711, EATON 1538A, B, C, D

       /etc/dtab:
	    #Name Unit# Addr   Vector Br Handler(s)	 # Comments
	    br	  ?	176710 254    5  brintr 	 # Eaton 1537/8

       major device number(s):
	    raw: 20
	    block: 11
       minor device encoding:
	    bits 0007 specify partition of BR drive
	    bits 0070 specify BR drive

DESCRIPTION

       Files  with minor device numbers 0 through 7 refer to various portions of drive 0; minor devices 8 through 15 refer to drive 1, etc.  There
       are four drive types supported by the Eaton BR1537 and BR1711 controllers, these are the 1538A (50 Mb), 1538B (80 Mb), 1538C (200  Mb)  and
       1538D (300 Mb).	Capacities are unformatted megabytes.  The standard device names begin with ``br'' followed by the drive number and then a
       letter a-h for partitions 0-7 respectively.  The character ? stands here for a drive number in the range 0-7.

       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 therefore 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 512 bytes (a disk sector).  Likewise seek
       calls should specify a multiple of 512 bytes.

DISK SUPPORT

       The size (in sectors) of the pseudo-disks on each drive are as follows:

       1538A partitions:
	    disk   length      cyls	     comments
	    br?a    18260   0  - 165	     1538A has 22 sec/trk, 5 trk/cyl
	    br?b    12210  166 - 276
	    br?c    59180  277 - 814
	    br?d    unused
	    br?e    unused
	    br?f    unused
	    br?g    unused
	    br?h    89650   0  - 814

       1538B partitions:
	    disk   length      cyls	     comments
	    br?a    18400   0  - 114	     1538B has 32 sec/trk, 5 trk/cyl
	    br?b    12320  115 - 190
	    br?c    99840  191 - 814
	    br?d    unused
	    br?e    unused
	    br?f    unused
	    br?g    unused
	    br?h    99840   0  - 814

       1538C partitions:
	    disk   length      cyls	     comments
	    br?a    18392   0  - 43	     1538C has 22 sec/trk, 19 trk/cyl
	    br?b    12122  44  - 72
	    br?c   231990  73 - 627
	    br?d    78166 628 - 814
	    br?e    unused
	    br?f    unused
	    br?g    unused
	    br?h   340670   0  - 814

       1538D partitions:
	    disk   length      cyls	     comments
	    br?a    18240   0  - 29	     1538D has 32 sec/trk, 19 trk/cyl
	    br?b    12160  30  - 49
	    br?c   232256  50 - 431
	    br?d   232256 432 - 813
	    br?e    unused
	    br?f    unused
	    br?g    unused
	    br?h   495520   0  - 814

FILES

       /dev/br[0-7][a-h]   block files
       /dev/rbr[0-7][a-h]  raw files
       /dev/MAKEDEV	   script to create special files
       /dev/MAKEDEV.local  script to localize special files

SEE ALSO

       ra(4), ram(4), rk(4), rl(4), rx(4), si(4), xp(4), dtab(5), autoconfig(8)

DIAGNOSTICS

       br%d%c: hard error sn%d cs2=%b ds=%b er=%b.  An unrecoverable error occurred during transfer of the specified sector of the specified  disk
       partition.   The  contents  of  the cs2, ds and er registers are printed in octal and symbolically with bits decoded.  The error was either
       unrecoverable, or a large number of retry attempts (including offset positioning and drive recalibration) could not recover the error.

BUGS

       In raw I/O read and write(2) truncate file offsets to 512-byte block boundaries, 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 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.

       The  partition tables for the file systems should be read off of each pack, as they are never quite what any single installation would pre-
       fer, and this would make packs more portable.

       Only the 1538D (300Mb) disk has been used with this driver, the disktab(5) file and newfs(8) program only know about the 1538D.

3rd Berkeley Distribution					  August 20, 1988							     BR(4)