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 prefer, 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.