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BR(4)											    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  buf-
       fer.   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 multi-
       ple 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 trans-
       fer 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 prefer, and this would make packs more por-
       table.

       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)
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