1XP(4)                      Kernel Interfaces Manual                      XP(4)
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NAME

6       xp - generic SMD moving-head disk
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SYNOPSIS

9       /sys/conf/SYSTEM:
10            NXPC    xp_controllers # Number of controllers
11            NXPD    xp_drives      # RM02/03/05, RP04/05/06,
12                                   # CDC 9766, Fuji 160, etc.
13            BADSECT NO             # Bad sector handling (see BUGS)
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15       /etc/dtab:
16            #Name Unit# Addr   Vector Br Handler(s)      # Comments
17            xp    ?     176700 254    5  xpintr          # xp driver
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19       major device number(s):
20            raw: 19
21            block: 10
22       minor device encoding:
23            bits 0007 specify partition of XP drive
24            bits 0370 specify XP drive
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DESCRIPTION

27       The  xp  driver is a generic SMD storage module disk driver.  It can be
28       adapted to most SMD controllers although bootstrapping will not  neces‐
29       sarily  be  directly  possible.  The drives are numbered from 0 to n on
30       controller 0, from n+1 to m on controller 1, etc.  The drives may  have
31       different geometries.
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33       The  xp  driver  is  unique  amoungst  2BSD drivers in its numbering of
34       drives.  Other drivers (ra for example) number drives 0 thru 7 on  con‐
35       troller  1,  8 thru 15 on controller 2 and so on.  xp on the other hand
36       can have drives 0 and 1 on controller 1, drives 2, 3, 4 and 5  on  con‐
37       troller  2  and  drives  6, 7 and 8 on controller 3.  This is different
38       from boot's view of the world, so if you are booting  from  other  than
39       unit 0 you may have to experiment a bit.
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41       Files  with  minor device numbers 0 through 7 refer to various portions
42       of drive 0; minor devices 8 through 15 refer  to  drive  1,  etc.   The
43       standard  device  names  begin with ``xp'' followed by the drive number
44       and then a letter a-h for partitions 0-7 respectively.  The character ?
45       stands here for a drive number in the range 0-7.
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47       The block files access the disk via the system's normal buffering mech‐
48       anism and may be read and  written  without  regard  to  physical  disk
49       records.   There  is  also  a `raw' interface which provides for direct
50       transmission between the disk and the user's read or write  buffer.   A
51       single  read  or  write  call  results in exactly one I/O operation and
52       therefore raw I/O is considerably more efficient when  many  words  are
53       transmitted.   The  names of the raw files conventionally begin with an
54       extra `r.'
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56       In raw I/O the buffer must begin on a word (even) boundary, and  counts
57       should  be  a  multiple  of  512 bytes (a disk sector).  Likewise lseek
58       calls should specify a multiple of 512 bytes.
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DISK SUPPORT

61       Disks must be labeled using either the standalone disklabel program  on
62       the  boot  tape or with the disklabel(8) program.  The kernel no longer
63       attempts to determine the drive type and geometry, instead reading this
64       information  from  the  disklabel.  There are no partition tables coded
65       into the xp driver, these must be placed on the drive with disklabel.
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67       Special files should only be created for the partitions that are  actu‐
68       ally  used,  as  the overlap in these addresses could lead to confusion
69       otherwise.  Traditionally the xp?a partition is normally used  for  the
70       root  file system, the xp?b partition as a swap area, and the xp?c par‐
71       tition for pack-pack copying (it maps the entire disk).
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FILES

74       /dev/xp[0-7][a-h]   block files
75       /dev/rxp[0-7][a-h]  raw files
76       /dev/MAKEDEV        script to create special files
77       /dev/MAKEDEV.local  script to localize special files
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SEE ALSO

80       hk(4), ra(4), ram(4), rk(4), rl(4), rp(4), rx(4), si(4), dtab(5), auto‐
81       config(8), newfs(8)
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DIAGNOSTICS

84       xp%d%c: hard error sn%d cs2=%b er1=%b.  An unrecoverable error occurred
85       during transfer of the specified sector of the  specified  disk  parti‐
86       tion.   The  contents  of  the  two error registers are also printed in
87       octal and symbolically with bits decoded.  The error was  either  unre‐
88       coverable,  or a large number of retry attempts (including offset posi‐
89       tioning and drive recalibration) could not recover the error.
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91       xp%d: write locked.  The write protect switch was set on the drive when
92       a write was attempted.  The write operation is not recoverable.
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94       xp%d%c:  soft ecc sn%d.  A recoverable ECC error occurred on the speci‐
95       fied sector of the specified disk partition.  This happens  normally  a
96       few  times a week.  If it happens more frequently than this the sectors
97       where the errors are occurring should be  checked  to  see  if  certain
98       cylinders  on the pack, spots on the carriage of the drive or heads are
99       indicated.
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101       xp%d: unknown device type 0%o.  The number in the  drive's  drive  type
102       register is unknown to the xp driver.
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BUGS

105       In  raw  I/O  read and write(2) truncate file offsets to 512-byte block
106       boundaries, and write scribbles  on  the  tail  of  incomplete  blocks.
107       Thus,  in  programs  that are likely to access raw devices, read, write
108       and lseek(2) should always deal in 512-byte multiples.
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110       DEC-standard error logging should be supported.
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112       The kernel uses partition 'h' to access the badblock information.  This
113       should have been 'c' except that almost all of the /etc/disktab entries
114       (and thus existing systems) use 'h' for this purpose.  Unless  you  are
115       very careful with disklabel|(8) (to make certain that no data partition
116       overlaps the badblock area) you should probably leave BADSECT undefined
117       in the kernel config file.
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1213rd Berkeley Distribution       August 14, 1995                          XP(4)
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