linux-old/Documentation/ide.txt
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   1ide.txt -- Information regarding the Enhanced IDE drive in Linux 2.2/2.3/2.4
   2===============================================================================
   3
   4   +-----------------------------------------------------------------+
   5   |  The hdparm utility for controlling various IDE features is     |
   6   |  packaged separately.  Look for it on popular linux FTP sites.  |
   7   +-----------------------------------------------------------------+
   8
   9See description later on below for handling BIG IDE drives with >1024 cyls.
  10
  11Major features of the 2.1/2.2 IDE driver ("NEW!" marks changes since 2.0.xx):
  12
  13NEW!    - support for IDE ATAPI *floppy* drives
  14        - support for IDE ATAPI *tape* drives, courtesy of Gadi Oxman
  15                (re-run MAKEDEV.ide to create the tape device entries in /dev/)
  16        - support for up to *four* IDE interfaces on one or more IRQs
  17        - support for any mix of up to *eight* IDE drives
  18        - support for reading IDE ATAPI cdrom drives (NEC,MITSUMI,VERTOS,SONY)
  19        - support for audio functions
  20        - auto-detection of interfaces, drives, IRQs, and disk geometries
  21                - "single" drives should be jumpered as "master", not "slave"
  22                  (both are now probed for)
  23        - support for BIOSs which report "more than 16 heads" on disk drives
  24        - uses LBA (slightly faster) on disk drives which support it
  25        - support for lots of fancy (E)IDE drive functions with hdparm utility
  26        - optional (compile time) support for 32-bit VLB data transfers
  27        - support for IDE multiple (block) mode (same as hd.c)
  28        - support for interrupt unmasking during I/O (better than hd.c)
  29        - improved handshaking and error detection/recovery
  30        - can co-exist with hd.c controlling the first interface
  31        - run-time selectable 32bit interface support (using hdparm-2.3)
  32        - support for reliable operation of buggy RZ1000 interfaces
  33                - PCI support is automatic when rz1000 support is configured
  34        - support for reliable operation of buggy CMD-640 interfaces
  35                - PCI support is automatic when cmd640 support is configured
  36                - for VLB, use kernel command line option:   ide0=cmd640_vlb
  37                - this support also enables the secondary i/f when needed
  38                - interface PIO timing & prefetch parameter support
  39        - experimental support for UMC 8672 interfaces
  40        - support for secondary interface on the FGI/Holtek HT-6560B VLB i/f
  41                - use kernel command line option:   ide0=ht6560b
  42        - experimental support for various IDE chipsets
  43                - use appropriate kernel command line option from list below
  44        - support for drives with a stuck WRERR_STAT bit
  45        - support for removable devices, including door lock/unlock
  46        - transparent support for DiskManager 6.0x and "Dynamic Disk Overlay"
  47        - works with Linux fdisk, LILO, loadlin, bootln, etc..
  48        - mostly transparent support for EZ-Drive disk translation software
  49                - to use LILO with EZ, install LILO on the linux partition
  50                  rather than on the master boot record, and then mark the
  51                  linux partition as "bootable" or "active" using fdisk.
  52                  (courtesy of Juha Laiho <jlaiho@ichaos.nullnet.fi>).
  53        - auto-detect of disk translations by examining partition table
  54        - ide-cd.c now compiles separate from ide.c
  55        - ide-cd.c now supports door locking and auto-loading.
  56                - Also preliminary support for multisession
  57                  and direct reads of audio data.
  58        - experimental support for Promise DC4030VL caching interface card
  59                - email thanks/problems to: peterd@pnd-pc.demon.co.uk
  60        - the hdparm-3.1 package can be used to set PIO modes for some chipsets.
  61NEW!    - support for setting PIO modes with the OPTi 82C621, courtesy of Jaromir Koutek.
  62NEW!    - support for loadable modules
  63NEW!    - optional SCSI host adapter emulation for ATAPI devices
  64NEW!    - generic PCI Bus-Master DMA support
  65NEW!            - works with most Pentium PCI systems, chipsets, add-on cards
  66NEW!            - works with regular DMA as well as Ultra DMA
  67NEW!            - automatically probes for all PCI IDE interfaces
  68NEW!    - generic support for using BIOS-configured Ultra-DMA (UDMA) transfers
  69
  70
  71***  IMPORTANT NOTICES:  BUGGY IDE CHIPSETS CAN CORRUPT DATA!!
  72***  =================
  73***  PCI versions of the CMD640 and RZ1000 interfaces are now detected
  74***  automatically at startup when PCI BIOS support is configured.
  75***
  76***  Linux disables the "prefetch" ("readahead") mode of the RZ1000
  77***  to prevent data corruption possible due to hardware design flaws.
  78***
  79***  For the CMD640, linux disables "IRQ unmasking" (hdparm -u1) on any
  80***  drive for which the "prefetch" mode of the CMD640 is turned on.
  81***  If "prefetch" is disabled (hdparm -p8), then "IRQ unmasking" can be
  82***  used again.
  83***
  84***  For the CMD640, linux disables "32bit I/O" (hdparm -c1) on any drive
  85***  for which the "prefetch" mode of the CMD640 is turned off.
  86***  If "prefetch" is enabled (hdparm -p9), then "32bit I/O" can be
  87***  used again.
  88***
  89***  The CMD640 is also used on some Vesa Local Bus (VLB) cards, and is *NOT*
  90***  automatically detected by Linux.  For safe, reliable operation with such
  91***  interfaces, one *MUST* use the "ide0=cmd640_vlb" kernel option.
  92***
  93***  Use of the "serialize" option is no longer necessary.
  94
  95This is the multiple IDE interface driver, as evolved from hd.c.
  96It supports up to six IDE interfaces, on one or more IRQs (usually 14 & 15).
  97There can be up to two drives per interface, as per the ATA-2 spec.
  98
  99Primary:    ide0, port 0x1f0; major=3;  hda is minor=0; hdb is minor=64
 100Secondary:  ide1, port 0x170; major=22; hdc is minor=0; hdd is minor=64
 101Tertiary:   ide2, port 0x1e8; major=33; hde is minor=0; hdf is minor=64
 102Quaternary: ide3, port 0x168; major=34; hdg is minor=0; hdh is minor=64
 103fifth..     ide4, usually PCI, probed
 104sixth..     ide5, usually PCI, probed
 105
 106To access devices on interfaces > ide0, device entries must first be
 107created in /dev for them.  To create such entries, simply run the included
 108shell script:   /usr/src/linux/scripts/MAKEDEV.ide
 109
 110Apparently many older releases of Slackware had incorrect entries
 111in /dev for hdc* and hdd* -- this can also be corrected by running MAKEDEV.ide
 112
 113ide.c automatically probes for most IDE interfaces (including all PCI ones),
 114for the drives/geometries attached to those interfaces, and for the
 115IRQ numbers being used by the interfaces (normally 14, 15 for ide0/ide1).
 116
 117For special cases, interfaces may be specified using kernel "command line"
 118options.  For example,
 119
 120        ide3=0x168,0x36e,10     /* ioports 0x168-0x16f,0x36e, irq 10 */
 121
 122Normally the irq number need not be specified, as ide.c will probe for it:
 123
 124        ide3=0x168,0x36e        /* ioports 0x168-0x16f,0x36e */
 125
 126The standard port, and irq values are these:
 127
 128        ide0=0x1f0,0x3f6,14
 129        ide1=0x170,0x376,15
 130        ide2=0x1e8,0x3ee,11
 131        ide3=0x168,0x36e,10
 132
 133Note that the first parameter reserves 8 contiguous ioports, whereas the
 134second value denotes a single ioport. If in doubt, do a 'cat /proc/ioports'.
 135
 136In all probability the device uses these ports and IRQs if it is attached
 137to the appropriate ide channel.  Pass the parameter for the correct ide
 138channel to the kernel, as explained above.
 139
 140Any number of interfaces may share a single IRQ if necessary, at a slight
 141performance penalty, whether on separate cards or a single VLB card.
 142The IDE driver automatically detects and handles this.  However, this may
 143or may not be harmful to your hardware.. two or more cards driving the same IRQ
 144can potentially burn each other's bus driver, though in practice this
 145seldom occurs.  Be careful, and if in doubt, don't do it!
 146
 147Drives are normally found by auto-probing and/or examining the CMOS/BIOS data.
 148For really weird situations, the apparent (fdisk) geometry can also be specified
 149on the kernel "command line" using LILO.  The format of such lines is:
 150
 151        hdx=cyls,heads,sects,wpcom,irq
 152or      hdx=cdrom
 153
 154where hdx can be any of hda through hdh, Three values are required
 155(cyls,heads,sects).  For example:
 156
 157        hdc=1050,32,64  hdd=cdrom
 158
 159either {hda,hdb} or {hdc,hdd}.  The results of successful auto-probing may
 160override the physical geometry/irq specified, though the "original" geometry
 161may be retained as the "logical" geometry for partitioning purposes (fdisk).
 162
 163If the auto-probing during boot time confuses a drive (ie. the drive works
 164with hd.c but not with ide.c), then an command line option may be specified
 165for each drive for which you'd like the drive to skip the hardware
 166probe/identification sequence.  For example:
 167
 168        hdb=noprobe
 169or
 170        hdc=768,16,32
 171        hdc=noprobe
 172
 173Note that when only one IDE device is attached to an interface,
 174it should be jumpered as "single" or "master", *not* "slave".
 175Many folks have had "trouble" with cdroms because of this requirement,
 176so ide.c now probes for both units, though success is more likely
 177when the drive is jumpered correctly.
 178
 179Courtesy of Scott Snyder and others, the driver supports ATAPI cdrom drives
 180such as the NEC-260 and the new MITSUMI triple/quad speed drives.
 181Such drives will be identified at boot time, just like a hard disk.
 182
 183If for some reason your cdrom drive is *not* found at boot time, you can force
 184the probe to look harder by supplying a kernel command line parameter
 185via LILO, such as:
 186
 187        hdc=cdrom       /* hdc = "master" on second interface */
 188or
 189        hdd=cdrom       /* hdd = "slave" on second interface */
 190
 191For example, a GW2000 system might have a hard drive on the primary
 192interface (/dev/hda) and an IDE cdrom drive on the secondary interface
 193(/dev/hdc).  To mount a CD in the cdrom drive, one would use something like:
 194
 195        ln -sf /dev/hdc /dev/cdrom
 196        mkdir /cd
 197        mount /dev/cdrom /cd -t iso9660 -o ro
 198
 199If, after doing all of the above, mount doesn't work and you see
 200errors from the driver (with dmesg) complaining about `status=0xff',
 201this means that the hardware is not responding to the driver's attempts
 202to read it.  One of the following is probably the problem:
 203
 204  - Your hardware is broken.
 205
 206  - You are using the wrong address for the device, or you have the
 207    drive jumpered wrong.  Review the configuration instructions above.
 208
 209  - Your IDE controller requires some nonstandard initialization sequence
 210    before it will work properly.  If this is the case, there will often
 211    be a separate MS-DOS driver just for the controller.  IDE interfaces
 212    on sound cards usually fall into this category.  Such configurations
 213    can often be made to work by first booting MS-DOS, loading the
 214    appropriate drivers, and then warm-booting linux (without powering
 215    off).  This can be automated using loadlin in the MS-DOS autoexec.
 216
 217If you always get timeout errors, interrupts from the drive are probably
 218not making it to the host.  Check how you have the hardware jumpered
 219and make sure it matches what the driver expects (see the configuration
 220instructions above).  If you have a PCI system, also check the BIOS
 221setup; I've had one report of a system which was shipped with IRQ 15
 222disabled by the BIOS.
 223
 224The kernel is able to execute binaries directly off of the cdrom,
 225provided it is mounted with the default block size of 1024 (as above).
 226
 227Please pass on any feedback on any of this stuff to the maintainer,
 228whose address can be found in linux/MAINTAINERS.
 229
 230Note that if BOTH hd.c and ide.c are configured into the kernel,
 231hd.c will normally be allowed to control the primary IDE interface.
 232This is useful for older hardware that may be incompatible with ide.c,
 233and still allows newer hardware to run on the 2nd/3rd/4th IDE ports
 234under control of ide.c.   To have ide.c also "take over" the primary
 235IDE port in this situation, use the "command line" parameter:  ide0=0x1f0
 236
 237The IDE driver is partly modularized.  The high level disk/cdrom/tape/floppy
 238drivers can always be compiled as loadable modules, the chipset drivers
 239can only be compiled into the kernel, and the core code (ide.c) can be
 240compiled as a loadable module provided no chipset support and no special
 241partition table translations are needed.
 242
 243When using ide.c/ide-tape.c as modules in combination with kerneld, add:
 244
 245        alias block-major-3 ide-probe
 246        alias char-major-37 ide-tape
 247
 248respectively to /etc/modules.conf.
 249
 250When ide.c is used as a module, you can pass command line parameters to the
 251driver using the "options=" keyword to insmod, while replacing any ',' with
 252';'.  For example:
 253
 254        insmod ide.o options="ide0=serialize ide2=0x1e8;0x3ee;11"
 255
 256
 257================================================================================
 258
 259Summary of ide driver parameters for kernel "command line":
 260----------------------------------------------------------
 261 "hdx="  is recognized for all "x" from "a" to "h", such as "hdc".
 262 "idex=" is recognized for all "x" from "0" to "3", such as "ide1".
 263
 264 "hdx=noprobe"          : drive may be present, but do not probe for it
 265 "hdx=none"             : drive is NOT present, ignore cmos and do not probe
 266 "hdx=nowerr"           : ignore the WRERR_STAT bit on this drive
 267 "hdx=cdrom"            : drive is present, and is a cdrom drive
 268 "hdx=cyl,head,sect"    : disk drive is present, with specified geometry
 269 "hdx=autotune"         : driver will attempt to tune interface speed
 270                                to the fastest PIO mode supported,
 271                                if possible for this drive only.
 272                                Not fully supported by all chipset types,
 273                                and quite likely to cause trouble with
 274                                older/odd IDE drives.
 275 "hdx=slow"             : insert a huge pause after each access to the data
 276                                port. Should be used only as a last resort.
 277 "hdx=swapdata"         : when the drive is a disk, byte swap all data
 278
 279 "hdxlun=xx"            : set the drive last logical unit
 280
 281 "idebus=xx"            : inform IDE driver of VESA/PCI bus speed in MHz,
 282                                where "xx" is between 20 and 66 inclusive,
 283                                used when tuning chipset PIO modes.
 284                                For PCI bus, 25 is correct for a P75 system,
 285                                30 is correct for P90,P120,P180 systems,
 286                                and 33 is used for P100,P133,P166 systems.
 287                                If in doubt, use idebus=33 for PCI.
 288                                As for VLB, it is safest to not specify it.
 289                                Bigger values are safer than smaller ones.
 290
 291 "idex=noprobe"         : do not attempt to access/use this interface
 292 "idex=base"            : probe for an interface at the addr specified,
 293                                where "base" is usually 0x1f0 or 0x170
 294                                and "ctl" is assumed to be "base"+0x206
 295 "idex=base,ctl"        : specify both base and ctl
 296 "idex=base,ctl,irq"    : specify base, ctl, and irq number
 297 "idex=autotune"        : driver will attempt to tune interface speed
 298                                to the fastest PIO mode supported,
 299                                for all drives on this interface.
 300                                Not fully supported by all chipset types,
 301                                and quite likely to cause trouble with
 302                                older/odd IDE drives.
 303 "idex=noautotune"      : driver will NOT attempt to tune interface speed
 304                                This is the default for most chipsets,
 305                                except the cmd640.
 306 "idex=serialize"       : do not overlap operations on idex and ide(x^1)
 307 "idex=reset"           : reset interface after probe
 308 "idex=dma"             : automatically configure/use DMA if possible.
 309 "idex=nohighio"        : don't use i/o to high memory addresses on this
 310                                interface. i/o to memory locations higher
 311                                than ~860MiB will be bounced.
 312
 313 The following are valid ONLY on ide0,
 314 and the defaults for the base,ctl ports must not be altered.
 315
 316 "ide0=dtc2278"         : probe/support DTC2278 interface
 317 "ide0=ht6560b"         : probe/support HT6560B interface
 318 "ide0=cmd640_vlb"      : *REQUIRED* for VLB cards with the CMD640 chip
 319                          (not for PCI -- automatically detected)
 320 "ide0=qd65xx"          : probe/support qd65xx interface
 321 "ide0=ali14xx"         : probe/support ali14xx chipsets (ALI M1439/M1445)
 322 "ide0=umc8672"         : probe/support umc8672 chipsets
 323
 324There may be more options than shown -- use the source, Luke!
 325
 326Everything else is rejected with a "BAD OPTION" message.
 327
 328================================================================================
 329
 330Some Terminology
 331----------------
 332IDE = Integrated Drive Electronics, meaning that each drive has a built-in
 333controller, which is why an "IDE interface card" is not a "controller card".
 334
 335IDE drives are designed to attach almost directly to the ISA bus of an AT-style
 336computer.  The typical IDE interface card merely provides I/O port address
 337decoding and tri-state buffers, although several newer localbus cards go much
 338beyond the basics.  When purchasing a localbus IDE interface, avoid cards with
 339an onboard BIOS and those which require special drivers.  Instead, look for a
 340card which uses hardware switches/jumpers to select the interface timing speed,
 341to allow much faster data transfers than the original 8MHz ISA bus allows.
 342
 343ATA = AT (the old IBM 286 computer) Attachment Interface, a draft American
 344National Standard for connecting hard drives to PCs.  This is the official
 345name for "IDE".
 346
 347The latest standards define some enhancements, known as the ATA-2 spec,
 348which grew out of vendor-specific "Enhanced IDE" (EIDE) implementations.
 349
 350ATAPI = ATA Packet Interface, a new protocol for controlling the drives,
 351similar to SCSI protocols, created at the same time as the ATA2 standard.
 352ATAPI is currently used for controlling CDROM and TAPE devices, and will
 353likely also soon be used for Floppy drives, removable R/W cartridges,
 354and for high capacity hard disk drives.
 355
 356How To Use *Big* ATA/IDE drives with Linux
 357------------------------------------------
 358The ATA Interface spec for IDE disk drives allows a total of 28 bits
 359(8 bits for sector, 16 bits for cylinder, and 4 bits for head) for addressing
 360individual disk sectors of 512 bytes each (in "Linear Block Address" (LBA)
 361mode, there is still only a total of 28 bits available in the hardware).
 362This "limits" the capacity of an IDE drive to no more than 128GB (Giga-bytes).
 363All current day IDE drives are somewhat smaller than this upper limit, and
 364within a few years, ATAPI disk drives will raise the limit considerably.
 365
 366All IDE disk drives "suffer" from a "16-heads" limitation:  the hardware has
 367only a four bit field for head selection, restricting the number of "physical"
 368heads to 16 or less.  Since the BIOS usually has a 63 sectors/track limit,
 369this means that all IDE drivers larger than 504MB (528Meg) must use a "physical"
 370geometry with more than 1024 cylinders.
 371
 372   (1024cyls * 16heads * 63sects * 512bytes/sector) / (1024 * 1024) == 504MB
 373
 374(Some BIOSs (and controllers with onboard BIOS) pretend to allow "32" or "64"
 375 heads per drive (discussed below), but can only do so by playing games with
 376 the real (hidden) geometry, which is always limited to 16 or fewer heads).
 377
 378This presents two problems to most systems:
 379
 380        1. The INT13 interface to the BIOS only allows 10-bits for cylinder
 381        addresses, giving a limit of 1024cyls for programs which use it.
 382
 383        2. The physical geometry fields of the disk partition table only
 384        allow 10-bits for cylinder addresses, giving a similar limit of 1024
 385        cyls for operating systems that do not use the "sector count" fields
 386        instead of the physical Cyl/Head/Sect (CHS) geometry fields.
 387
 388Neither of these limitations affects Linux itself, as it (1) does not use the
 389BIOS for disk access, and it (2) is clever enough to use the "sector count"
 390fields of the partition table instead of the physical CHS geometry fields.
 391
 392        a) Most folks use LILO to load linux.  LILO uses the INT13 interface
 393        to the BIOS to load the kernel at boot time.  Therefore, LILO can only
 394        load linux if the files it needs (usually just the kernel images) are
 395        located below the magic 1024 cylinder "boundary" (more on this later).
 396
 397        b) Many folks also like to have bootable DOS partitions on their
 398        drive(s).  DOS also uses the INT13 interface to the BIOS, not only
 399        for booting, but also for operation after booting.  Therefore, DOS
 400        can normally only access partitions which are contained entirely below
 401        the magic 1024 cylinder "boundary".
 402
 403There are at least seven commonly used schemes for kludging DOS to work
 404around this "limitation".  In the long term, the problem is being solved
 405by introduction of an alternative BIOS interface that does not have the
 406same limitations as the INT13 interface.  New versions of DOS are expected
 407to detect and use this interface in systems whose BIOS provides it.
 408
 409But in the present day, alternative solutions are necessary.
 410
 411The most popular solution in newer systems is to have the BIOS shift bits
 412between the cylinder and head number fields.  This is activated by entering
 413a translated logical geometry into the BIOS/CMOS setup for the drive.
 414Thus, if the drive has a geometry of 2100/16/63 (CHS), then the BIOS could
 415present a "logical" geometry of 525/64/63 by "shifting" two bits from the
 416cylinder number into the head number field for purposes of the partition table,
 417CMOS setup, and INT13 interfaces.  Linux kernels 1.1.39 and higher detect and
 418"handle" this translation automatically, making this a rather painless solution
 419for the 1024 cyls problem.  If for some reason Linux gets confused (unlikely),
 420then use the kernel command line parameters to pass the *logical* geometry,
 421as in:  hda=525,64,63
 422
 423If the BIOS does not support this form of drive translation, then several
 424options remain, listed below in order of popularity:
 425
 426        - use a partition below the 1024 cyl boundary to hold the linux
 427        boot files (kernel images and /boot directory), and place the rest
 428        of linux anywhere else on the drive.  These files can reside in a DOS
 429        partition, or in a tailor-made linux boot partition.
 430        - use DiskManager software from OnTrack, supplied free with
 431        many new hard drive purchases.
 432        - use EZ-Drive software (similar to DiskManager).  Note though,
 433        that LILO must *not* use the MBR when EZ-Drive is present.
 434        Instead, install LILO on the first sector of your linux partition,
 435        and mark it as "active" or "bootable" with fdisk.
 436        - boot from a floppy disk instead of the hard drive (takes 10 seconds).
 437
 438If you cannot use drive translation, *and* your BIOS also restricts you to
 439entering no more than 1024 cylinders in the geometry field in the CMOS setup,
 440then just set it to 1024.  As of v3.5 of this driver, Linux automatically
 441determines the *real* number of cylinders for fdisk to use, allowing easy
 442access to the full disk capacity without having to fiddle around.
 443
 444Regardless of what you do, all DOS partitions *must* be contained entirely
 445within the first 1024 logical cylinders.  For a 1Gig WD disk drive, here's
 446a good "half and half" partitioning scheme to start with:
 447
 448        geometry = 2100/16/63
 449        /dev/hda1 from cyl    1 to  992         dos
 450        /dev/hda2 from cyl  993 to 1023         swap
 451        /dev/hda3 from cyl 1024 to 2100         linux
 452
 453To ensure that LILO can boot linux, the boot files (kernel and /boot/*)
 454must reside within the first 1024 cylinders of the drive.  If your linux
 455root partition is *not* completely within the first 1024 cyls (quite common),
 456then you can use LILO to boot linux from files on your DOS partition
 457by doing the following after installing Slackware (or whatever):
 458
 459        0. Boot from the "boot floppy" created during the installation
 460        1. Mount your DOS partition as /dos (and stick it in /etc/fstab)
 461        2. Move /boot to /dos/boot with:  cp -a /boot /dos ; rm -r /boot
 462        3. Create a symlink for LILO to use with:  ln -s /dos/boot /boot
 463        4. Move your kernel (/vmlinuz) to /boot/vmlinuz:  mv /vmlinuz /boot
 464        5. Edit /etc/lilo.conf to change /vmlinuz to /boot/vmlinuz
 465        6. Re-run LILO with:  lilo
 466
 467        A danger with this approach is that whenever an MS-DOS "defragmentation"
 468        program is run (like Norton "speeddisk"), it may move the Linux boot
 469        files around, confusing LILO and making the (Linux) system unbootable.
 470        Be sure to keep a kernel "boot floppy" at hand for such circumstances.
 471        A possible workaround is to mark the Linux files as S+H+R (System,
 472        Hidden, Readonly), to prevent most defragmentation programs from
 473        moving the files around.
 474
 475If you "don't do DOS", then partition as you please, but remember to create
 476a small partition to hold the /boot directory (and vmlinuz) as described above
 477such that they stay within the first 1024 cylinders.
 478
 479Note that when creating partitions that span beyond cylinder 1024,
 480Linux fdisk will complain about "Partition X has different physical/logical
 481endings" and emit messages such as "This is larger than 1024, and may cause
 482problems with some software".   Ignore this for linux partitions.  The "some
 483software" refers to DOS, the BIOS, and LILO, as described previously.
 484
 485Western Digital ships a "DiskManager 6.03" diskette with all of their big
 486hard drives.  Use BIOS translation instead of this if possible, as it is a
 487more generally compatible method of achieving the same results (DOS access
 488to the entire disk).  However, if you must use DiskManager, it now works
 489with Linux 1.3.x in most cases.  Let me know if you still have trouble.
 490
 491My recommendations to anyone who asks about NEW systems are:
 492
 493        - buy a motherboard that uses the Intel Triton chipset -- very common.
 494        - use IDE for the first two drives, placing them on separate interfaces.
 495                - very fast 7200rpm drives are now available
 496                (though many problems have been reported with Seagate ones).
 497        - place the IDE cdrom drive as slave on either interface.
 498        - if additional disks are to be connected, consider your needs:
 499                - fileserver?  Buy a SC200 SCSI adaptor for the next few drives.
 500                - personal system?  Use IDE for the next two drives.
 501                - still not enough?  Keep adding SC200 SCSI cards as needed.
 502
 503Most manufacturers make both IDE and SCSI versions of each of their drives.
 504The IDE ones are usually as fast and cheaper, due to lower command overhead
 505and the higher data transfer speed of UDMA2.  But fast/ultrawide/superlative
 506SCSI is still king of the heap, especially for servers, if you've got the bucks.
 507
 508mlord@pobox.com
 509--
 510For current maintainers of this stuff, see the linux/MAINTAINERS file.
 511
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