SI(4)		    UNIX Programmer's Manual		    SI(4)



NAME
     si - SI 9500/CDC 9766 moving head disk

SYNOPSIS
     /sys/conf/SYSTEM:
	  NSI  _s_i__d_r_i_v_e_s # 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 par-
     titions 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 there-
     fore 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 sec-
     tor).  Likewise _s_e_e_k 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:











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SI(4)		    UNIX Programmer's Manual		    SI(4)



     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 indi-
     cated lengths are correct.  Partition ``h'' must be used to
     access the bad block forwarding area.  N.B.: the _s_i 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 _r_e_a_d and _w_r_i_t_e(2) truncate file offsets to 512-
     byte block boundaries, and _w_r_i_t_e scribbles on the tail of
     incomplete blocks.  Thus, in programs that are likely to
     access raw devices, _r_e_a_d, _w_r_i_t_e and _l_s_e_e_k(2) should always



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SI(4)		    UNIX Programmer's Manual		    SI(4)



     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.

















































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