SI(4)							     Kernel Interfaces Manual							     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 par-
       tition.	The contents of the two error registers are also printed in octal and symbolically with bits decoded.  The error was either  unre-
       coverable, 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 par-
       tition.	The contents of the two error registers are also printed in octal and symbolically with bits decoded.  The error was either  unre-
       coverable, 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  pre-
       fer, and this would make packs more portable.

3rd Berkeley Distribution					  August 20, 1987							     SI(4)