ide.txt

嵌入式系统设计与实例开发实验教材二源码 多线程应用程序设计 串行端口程序设计 AD接口实验 CAN总线通信实验 GPS通信实验 Linux内核移植与编译实验 IC卡读写实验 SD驱动使

================================================================================

Summary of ide driver parameters for kernel "command line":
----------------------------------------------------------
 "hdx="  is recognized for all "x" from "a" to "h", such as "hdc".
 "idex=" is recognized for all "x" from "0" to "3", such as "ide1".

 "hdx=noprobe"		: drive may be present, but do not probe for it
 "hdx=none"		: drive is NOT present, ignore cmos and do not probe
 "hdx=nowerr"		: ignore the WRERR_STAT bit on this drive
 "hdx=cdrom"		: drive is present, and is a cdrom drive
 "hdx=cyl,head,sect"	: disk drive is present, with specified geometry
 "hdx=autotune"		: driver will attempt to tune interface speed
				to the fastest PIO mode supported,
				if possible for this drive only.
				Not fully supported by all chipset types,
				and quite likely to cause trouble with
				older/odd IDE drives.
 "hdx=slow"		: insert a huge pause after each access to the data
				port. Should be used only as a last resort.
 "hdx=swapdata"		: when the drive is a disk, byte swap all data

 "hdxlun=xx"		: set the drive last logical unit

 "idebus=xx"		: inform IDE driver of VESA/PCI bus speed in MHz,
				where "xx" is between 20 and 66 inclusive,
				used when tuning chipset PIO modes.
				For PCI bus, 25 is correct for a P75 system,
				30 is correct for P90,P120,P180 systems,
				and 33 is used for P100,P133,P166 systems.
				If in doubt, use idebus=33 for PCI.
				As for VLB, it is safest to not specify it.
				Bigger values are safer than smaller ones.

 "idex=noprobe"		: do not attempt to access/use this interface
 "idex=base"		: probe for an interface at the addr specified,
				where "base" is usually 0x1f0 or 0x170
				and "ctl" is assumed to be "base"+0x206
 "idex=base,ctl"	: specify both base and ctl
 "idex=base,ctl,irq"	: specify base, ctl, and irq number
 "idex=autotune"	: driver will attempt to tune interface speed
				to the fastest PIO mode supported,
				for all drives on this interface.
				Not fully supported by all chipset types,
				and quite likely to cause trouble with
				older/odd IDE drives.
 "idex=noautotune"	: driver will NOT attempt to tune interface speed
				This is the default for most chipsets,
				except the cmd640.
 "idex=serialize"	: do not overlap operations on idex and ide(x^1)
 "idex=reset"		: reset interface after probe
 "idex=dma"		: automatically configure/use DMA if possible.

 The following are valid ONLY on ide0,
 and the defaults for the base,ctl ports must not be altered.

 "ide0=dtc2278"		: probe/support DTC2278 interface
 "ide0=ht6560b"		: probe/support HT6560B interface
 "ide0=cmd640_vlb"	: *REQUIRED* for VLB cards with the CMD640 chip
			  (not for PCI -- automatically detected)
 "ide0=qd65xx"		: probe/support qd65xx interface
 "ide0=ali14xx"		: probe/support ali14xx chipsets (ALI M1439/M1445)
 "ide0=umc8672"		: probe/support umc8672 chipsets

There may be more options than shown -- use the source, Luke!

Everything else is rejected with a "BAD OPTION" message.

================================================================================

Some Terminology
----------------
IDE = Integrated Drive Electronics, meaning that each drive has a built-in
controller, which is why an "IDE interface card" is not a "controller card".

IDE drives are designed to attach almost directly to the ISA bus of an AT-style
computer.  The typical IDE interface card merely provides I/O port address
decoding and tri-state buffers, although several newer localbus cards go much
beyond the basics.  When purchasing a localbus IDE interface, avoid cards with
an onboard BIOS and those which require special drivers.  Instead, look for a
card which uses hardware switches/jumpers to select the interface timing speed,
to allow much faster data transfers than the original 8MHz ISA bus allows.

ATA = AT (the old IBM 286 computer) Attachment Interface, a draft American
National Standard for connecting hard drives to PCs.  This is the official
name for "IDE".

The latest standards define some enhancements, known as the ATA-2 spec,
which grew out of vendor-specific "Enhanced IDE" (EIDE) implementations.

ATAPI = ATA Packet Interface, a new protocol for controlling the drives,
similar to SCSI protocols, created at the same time as the ATA2 standard.
ATAPI is currently used for controlling CDROM and TAPE devices, and will
likely also soon be used for Floppy drives, removable R/W cartridges,
and for high capacity hard disk drives.

How To Use *Big* ATA/IDE drives with Linux
------------------------------------------
The ATA Interface spec for IDE disk drives allows a total of 28 bits
(8 bits for sector, 16 bits for cylinder, and 4 bits for head) for addressing
individual disk sectors of 512 bytes each (in "Linear Block Address" (LBA)
mode, there is still only a total of 28 bits available in the hardware).
This "limits" the capacity of an IDE drive to no more than 128GB (Giga-bytes).
All current day IDE drives are somewhat smaller than this upper limit, and
within a few years, ATAPI disk drives will raise the limit considerably.

All IDE disk drives "suffer" from a "16-heads" limitation:  the hardware has
only a four bit field for head selection, restricting the number of "physical"
heads to 16 or less.  Since the BIOS usually has a 63 sectors/track limit,
this means that all IDE drivers larger than 504MB (528Meg) must use a "physical"
geometry with more than 1024 cylinders.

   (1024cyls * 16heads * 63sects * 512bytes/sector) / (1024 * 1024) == 504MB

(Some BIOSs (and controllers with onboard BIOS) pretend to allow "32" or "64"
 heads per drive (discussed below), but can only do so by playing games with
 the real (hidden) geometry, which is always limited to 16 or fewer heads).

This presents two problems to most systems:

	1. The INT13 interface to the BIOS only allows 10-bits for cylinder
	addresses, giving a limit of 1024cyls for programs which use it.

	2. The physical geometry fields of the disk partition table only
	allow 10-bits for cylinder addresses, giving a similar limit of 1024
	cyls for operating systems that do not use the "sector count" fields
	instead of the physical Cyl/Head/Sect (CHS) geometry fields.

Neither of these limitations affects Linux itself, as it (1) does not use the
BIOS for disk access, and it (2) is clever enough to use the "sector count"
fields of the partition table instead of the physical CHS geometry fields.

	a) Most folks use LILO to load linux.  LILO uses the INT13 interface
	to the BIOS to load the kernel at boot time.  Therefore, LILO can only
	load linux if the files it needs (usually just the kernel images) are
	located below the magic 1024 cylinder "boundary" (more on this later).

	b) Many folks also like to have bootable DOS partitions on their
	drive(s).  DOS also uses the INT13 interface to the BIOS, not only
	for booting, but also for operation after booting.  Therefore, DOS
	can normally only access partitions which are contained entirely below
	the magic 1024 cylinder "boundary".

There are at least seven commonly used schemes for kludging DOS to work
around this "limitation".  In the long term, the problem is being solved
by introduction of an alternative BIOS interface that does not have the
same limitations as the INT13 interface.  New versions of DOS are expected
to detect and use this interface in systems whose BIOS provides it.

But in the present day, alternative solutions are necessary.

The most popular solution in newer systems is to have the BIOS shift bits
between the cylinder and head number fields.  This is activated by entering
a translated logical geometry into the BIOS/CMOS setup for the drive.
Thus, if the drive has a geometry of 2100/16/63 (CHS), then the BIOS could
present a "logical" geometry of 525/64/63 by "shifting" two bits from the
cylinder number into the head number field for purposes of the partition table,
CMOS setup, and INT13 interfaces.  Linux kernels 1.1.39 and higher detect and
"handle" this translation automatically, making this a rather painless solution
for the 1024 cyls problem.  If for some reason Linux gets confused (unlikely),
then use the kernel command line parameters to pass the *logical* geometry,
as in:  hda=525,64,63

If the BIOS does not support this form of drive translation, then several
options remain, listed below in order of popularity:

	- use a partition below the 1024 cyl boundary to hold the linux
	boot files (kernel images and /boot directory), and place the rest
	of linux anywhere else on the drive.  These files can reside in a DOS
	partition, or in a tailor-made linux boot partition.
	- use DiskManager software from OnTrack, supplied free with
	many new hard drive purchases.
	- use EZ-Drive software (similar to DiskManager).  Note though,
	that LILO must *not* use the MBR when EZ-Drive is present.
	Instead, install LILO on the first sector of your linux partition,
	and mark it as "active" or "bootable" with fdisk.
	- boot from a floppy disk instead of the hard drive (takes 10 seconds).

If you cannot use drive translation, *and* your BIOS also restricts you to
entering no more than 1024 cylinders in the geometry field in the CMOS setup,
then just set it to 1024.  As of v3.5 of this driver, Linux automatically
determines the *real* number of cylinders for fdisk to use, allowing easy
access to the full disk capacity without having to fiddle around.

Regardless of what you do, all DOS partitions *must* be contained entirely
within the first 1024 logical cylinders.  For a 1Gig WD disk drive, here's
a good "half and half" partitioning scheme to start with:

	geometry = 2100/16/63
	/dev/hda1 from cyl    1 to  992		dos
	/dev/hda2 from cyl  993 to 1023		swap
	/dev/hda3 from cyl 1024 to 2100		linux

To ensure that LILO can boot linux, the boot files (kernel and /boot/*)
must reside within the first 1024 cylinders of the drive.  If your linux
root partition is *not* completely within the first 1024 cyls (quite common),
then you can use LILO to boot linux from files on your DOS partition
by doing the following after installing Slackware (or whatever):

	0. Boot from the "boot floppy" created during the installation
        1. Mount your DOS partition as /dos (and stick it in /etc/fstab)
        2. Move /boot to /dos/boot with:  cp -a /boot /dos ; rm -r /boot
        3. Create a symlink for LILO to use with:  ln -s /dos/boot /boot
        4. Move your kernel (/vmlinuz) to /boot/vmlinuz:  mv /vmlinuz /boot
        5. Edit /etc/lilo.conf to change /vmlinuz to /boot/vmlinuz
        6. Re-run LILO with:  lilo

	A danger with this approach is that whenever an MS-DOS "defragmentation"
	program is run (like Norton "speeddisk"), it may move the Linux boot
	files around, confusing LILO and making the (Linux) system unbootable.
	Be sure to keep a kernel "boot floppy" at hand for such circumstances.
	A possible workaround is to mark the Linux files as S+H+R (System,
	Hidden, Readonly), to prevent most defragmentation programs from
	moving the files around.

If you "don't do DOS", then partition as you please, but remember to create
a small partition to hold the /boot directory (and vmlinuz) as described above
such that they stay within the first 1024 cylinders.

Note that when creating partitions that span beyond cylinder 1024,
Linux fdisk will complain about "Partition X has different physical/logical
endings" and emit messages such as "This is larger than 1024, and may cause
problems with some software".   Ignore this for linux partitions.  The "some
software" refers to DOS, the BIOS, and LILO, as described previously.

Western Digital ships a "DiskManager 6.03" diskette with all of their big
hard drives.  Use BIOS translation instead of this if possible, as it is a
more generally compatible method of achieving the same results (DOS access
to the entire disk).  However, if you must use DiskManager, it now works
with Linux 1.3.x in most cases.  Let me know if you still have trouble.

My recommendations to anyone who asks about NEW systems are:

        - buy a motherboard that uses the Intel Triton chipset -- very common.
        - use IDE for the first two drives, placing them on separate interfaces.
		- very fast 7200rpm drives are now available
		(though many problems have been reported with Seagate ones).
	- place the IDE cdrom drive as slave on either interface.
        - if additional disks are to be connected, consider your needs:
                - fileserver?  Buy a SC200 SCSI adaptor for the next few drives.
                - personal system?  Use IDE for the next two drives.
                - still not enough?  Keep adding SC200 SCSI cards as needed.

Most manufacturers make both IDE and SCSI versions of each of their drives.
The IDE ones are usually as fast and cheaper, due to lower command overhead
and the higher data transfer speed of UDMA2.  But fast/ultrawide/superlative
SCSI is still king of the heap, especially for servers, if you've got the bucks.

[e-mail]
--
For current maintainers of this stuff, see the linux/MAINTAINERS file.