SI(4)

NAME
si - SI 9500/CDC 9766 moving head disk

SYNOPSIS
/sys/conf/SYSTEM:
	NSI	si_drives	# SI 9500 driver for CDC 9766 disks
/etc/dtab:
	#Name	Unit#	Addr	Vector	Br	Handler(s)		# Comments
	si	?	176700	170	5	siintr		# si9500
major device number(s):
	raw: 18
	block: 9
minor device encoding:
	bits 0007 specify partition of SI drive
	bits 0070 specify SI 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. The standard device names begin with ``si'' 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 origin and size (in sectors) of the pseudo-disks on each drive are as follows:

SI 9500/CDC9766 partitions:
	disk	 start	length	     cyls	comments
	xp?a	     0	  9120	  0 -  14	/
	xp?b	  9120	  9120	 15 -  29	swap
	xp?c	 18240	234080	 30 - 414
	xp?d	252320	247906	415 - 822*
	xp?e	 18240	164160	 30 - 299	/usr
	xp?f	182400	152000	300 - 549
	xp?g	334400	165826	550 - 822*
	xp?h	     0	500384	  0 - 822	whole pack

Those partitions marked with an asterisk (``*'') actually stop short of the indicated ending cylinder to protect any bad block forwarding information on the packs. The indicated lengths are correct. Partition ``h'' must be used to access the bad block forwarding area. N.B.: the si driver does not support bad block forwarding; the space is reserved in the event bad block forwarding is ever added to the driver.

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

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

DIAGNOSTICS
si%d%c: hard error sn%d cnr=%b err=%b. An unrecoverable error occurred 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 (including offset positioning and drive recalibration) could not recover the error.

si%d%c: hard error sn%d ssr=%b err=%b. An unrecoverable error occurred 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 (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.

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.