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diff --git a/share/doc/handbook/esdi.sgml b/share/doc/handbook/esdi.sgml deleted file mode 100644 index a7ca386..0000000 --- a/share/doc/handbook/esdi.sgml +++ /dev/null @@ -1,421 +0,0 @@ -<!-- $Id$ --> -<!-- The FreeBSD Documentation Project --> - -<!-- - <title>An introduction to ESDI hard disks and their use with FreeBSD</title> - <author>(c) 1995, Wilko Bulte, <tt/wilko@yedi.iaf.nl/ - <date>Tue Sep 12 20:48:44 MET DST 1995</date> - - Copyright 1995, Wilko C. Bulte, Arnhem, The Netherlands - - <abstract> - This document describes the use of ESDI disks in combination - with the FreeBSD operating system. Contrary to popular - belief, this is possible and people are using ESDI based - systems successfully! This document tries to explain you - how to do this. - - If you find something missing, plain wrong or have useful - comments on how to improve - the document please send mail to <tt/wilko@yedi.iaf.nl/ - </abstract> ---> - - <sect1><heading>Using ESDI hard disks<label id="esdi"></heading> - - <p><em>Copyright © 1995, &a.wilko;.<newline>24 September 1995.</em> - - ESDI is an acronym that means Enhanced Small Device Interface. - It is loosely based on the good old ST506/412 interface originally - devised by Seagate Technology, the makers of the first affordable - 5.25" winchester disk. - - The acronym says Enhanced, and rightly so. In the first place - the speed of the interface is higher, 10 or 15 Mbits/second - instead of the 5 Mbits/second of ST412 interfaced drives. - Secondly some higher level commands are added, making the ESDI - interface somewhat 'smarter' to the operating system driver - writers. It is by no means as smart as SCSI by the way. ESDI - is standardized by ANSI. - - Capacities of the drives are boosted by putting more sectors - on each track. Typical is 35 sectors per track, high capacity - drives I have seen were up to 54 sectors/track. - - Although ESDI has been largely obsoleted by IDE and SCSI interfaces, - the availability of free or cheap surplus drives makes them - ideal for low (or now) budget systems. - - <sect2><heading>Concepts of ESDI</heading> - <p> - <sect3><heading>Physical connections</heading> - <p> - The ESDI interface uses two cables connected to each drive. - One cable is a 34 pin flat cable edge connector that carries - the command and status signals from the controller to the - drive and vice-versa. The command cable is daisy chained - between all the drives. So, it forms a bus onto which all - drives are connected. - - The second cable is a 20 pin flat cable edge connector that - carries the data to and from the drive. This cable is radially - connected, so each drive has its own direct connection to the - controller. - - To the best of my knowledge PC ESDI controllers are limited - to using a maximum of 2 drives per controller. This is - compatibility feature(?) left over from the WD1003 standard - that reserves only a single bit for device addressing. - - <sect3><heading>Device addressing</heading> - <p> - On each command cable a maximum of 7 devices and 1 controller - can be present. To enable the controller to uniquely - identify which drive it addresses, each ESDI device is equipped - with jumpers or switches to select the devices address. - - On PC type controllers the first drive is set to address 0, - the second disk to address 1. <it>Always make sure</it> you - set each disk to an unique address! So, on a PC with its - two drives/controller maximum the first drive is drive 0, the - second is drive 1. - - <sect3><heading>Termination</heading> - <p> - The daisy chained command cable (the 34 pin cable remember?) - needs to be terminated at the last drive on the chain. - For this purpose ESDI drives come with a termination resistor - network that can be removed or disabled by a jumper when it - is not used. - - So, one and <it>only</it> one drive, the one at - the farthest end of the command - cable has its terminator installed/enabled. The controller - automatically terminates the other end of the cable. - Please note that this implies that the controller must be - at one end of the cable and <it>not</it> in the middle. - - <sect2><heading>Using ESDI disks with FreeBSD</heading> - <p> - Why is ESDI such a pain to get working in the first place? - - People who tried ESDI disks with FreeBSD are known to have - developed a profound sense of frustration. A combination of - factors works against you to produce effects that are - hard to understand when you have never seen them before. - - This has also led to the popular legend ESDI and FreeBSD - is a plain NO-GO. - The following sections try to list all the pitfalls and - solutions. - - <sect3><heading>ESDI speed variants</heading> - <p> - As briefly mentioned before, ESDI comes in two speed flavors. - The older drives and controllers use a 10 Mbits/second - data transfer rate. Newer stuff uses 15 Mbits/second. - - It is not hard to imagine that 15 Mbits/second drive cause - problems on controllers laid out for 10 Mbits/second. - As always, consult your controller <it>and</it> drive - documentation to see if things match. - - <sect3><heading>Stay on track</heading> - <p> - Mainstream ESDI drives use 34 to 36 sectors per track. - Most (older) controllers cannot handle more than this - number of sectors. - Newer, higher capacity, drives use higher numbers of sectors - per track. For instance, I own a 670 Mb drive that has - 54 sectors per track. - - In my case, the controller could not handle this number - of sectors. It proved to work well except that it only - used 35 sectors on each track. This meant losing a - lot of disk space. - - Once again, check the documentation of your hardware for - more info. Going out-of-spec like in the example might - or might not work. Give it a try or get another more - capable controller. - - <sect3><heading>Hard or soft sectoring</heading> - <p> - Most ESDI drives allow hard or soft sectoring to be - selected using a jumper. Hard sectoring means that the - drive will produce a sector pulse on the start of each - new sector. The controller uses this pulse to tell when - it should start to write or read. - - Hard sectoring allows a selection of sector size (normally - 256, 512 or 1024 bytes per formatted sector). FreeBSD uses - 512 byte sectors. The number of sectors per track also varies - while still using the same number of bytes per formatted sector. - The number of <em>unformatted</em> bytes per sector varies, - dependent on your controller it needs more or less overhead - bytes to work correctly. Pushing more sectors on a track - of course gives you more usable space, but might give - problems if your controller needs more bytes than the - drive offers. - - In case of soft sectoring, the controller itself determines - where to start/stop reading or writing. For ESDI - hard sectoring is the default (at least on everything - I came across). I never felt the urge to try soft sectoring. - - In general, experiment with sector settings before you install - FreeBSD because you need to re-run the low-level format - after each change. - - <sect3><heading>Low level formatting</heading> - <p> - ESDI drives need to be low level formatted before they - are usable. A reformat is needed whenever you figgle - with the number of sectors/track jumpers or the - physical orientation of the drive (horizontal, vertical). - So, first think, then format. - The format time must not be underestimated, for big - disks it can take hours. - - After a low level format, a surface scan is done to - find and flag bad sectors. Most disks have a - manufacturer bad block list listed on a piece of paper - or adhesive sticker. In addition, on most disks the - list is also written onto the disk. - Please use the manufacturer's list. It is much easier - to remap a defect now than after FreeBSD is installed. - - Stay away from low-level formatters that mark all - sectors of a track as bad as soon as they find one - bad sector. Not only does this waste space, it also - and more importantly causes you grief with bad144 - (see the section on bad144). - - <sect3><heading>Translations</heading> - <p> - Translations, although not exclusively a ESDI-only problem, - might give you real trouble. - Translations come in multiple flavors. Most of them - have in common that they attempt to work around the - limitations posed upon disk geometries by the original - IBM PC/AT design (thanks IBM!). - - First of all there is the (in)famous 1024 cylinder limit. - For a system to be able to boot, the stuff (whatever - operating system) must be in the first 1024 cylinders - of a disk. Only 10 bits are available to encode the - cylinder number. For the number of sectors the limit - is 64 (0-63). - When you combine the 1024 cylinder limit with the 16 head - limit (also a design feature) you max out at fairly limited - disk sizes. - - To work around this problem, the manufacturers of ESDI - PC controllers added a BIOS prom extension on their boards. - This BIOS extension handles disk I/O for booting (and for - some operating systems <it>all</it> disk I/O) by using - translation. For instance, a big drive might be presented - to the system as having 32 heads and 64 sectors/track. - The result is that the number of cylinders is reduced to - something below 1024 and is therefore usable by the system - without problems. - It is noteworthy to know that FreeBSD does not use the - BIOS after its kernel has started. More on this later. - - A second reason for translations is the fact that most - older system BIOSes could only handle drives with 17 sectors - per track (the old ST412 standard). Newer system BIOSes - usually have a user-defined drive type (in most cases this is - drive type 47). - - <em>Whatever you do to translations after reading this document, - keep in mind that if you have multiple operating systems on the - same disk, all must use the same translation</em> - - While on the subject of translations, I have seen one controller - type (but there are probably more like this) offer the option - to logically split a drive in multiple partitions as a BIOS - option. I had select 1 drive == 1 partition because this - controller wrote this info onto the disk. On power-up it - read the info and presented itself to the system based on - the info from the disk. - - <sect3><heading>Spare sectoring</heading> - <p> - Most ESDI controllers offer the possibility to remap bad sectors. - During/after the low-level format of the disk bad sectors are - marked as such, and a replacement sector is put in place - (logically of course) of the bad one. - - In most cases the remapping is done by using N-1 sectors on - each track for actual data storage, and sector N itself is - the spare sector. N is the total number of sectors physically - available on the track. - The idea behind this is that the operating system sees - a 'perfect' disk without bad sectors. In the case of - FreeBSD this concept is not usable. - - The problem is that the translation from <it>bad</it> to <it>good</it> - is performed by the BIOS of the ESDI controller. FreeBSD, - being a true 32 bit operating system, does not use the BIOS - after it has been booted. Instead, it has device drivers that - talk directly to the hardware. - - <em>So: don't use spare sectoring, bad block remapping or - whatever it may be called by the controller manufacturer when you - want to use the disk for FreeBSD.</em> - - <sect3><heading>Bad block handling</heading> - <p> - The preceding section leaves us with a problem. The controller's - bad block handling is not usable and still FreeBSD's filesystems - assume perfect media without any flaws. - To solve this problem, FreeBSD use the <it>bad144</it> tool. - Bad144 (named after a Digital Equipment standard for bad block - handling) scans a FreeBSD slice for bad blocks. Having found - these bad blocks, it writes a table with the offending block - numbers to the end of the FreeBSD slice. - - When the disk is in operation, the disk accesses are checked - against the table read from the disk. Whenever a block number - is requested that is in the bad144 list, a replacement block - (also from the end of the FreeBSD slice) is used. - In this way, the bad144 replacement scheme presents 'perfect' - media to the FreeBSD filesystems. - - There are a number of potential pitfalls associated with - the use of bad144. - First of all, the slice cannot have more than 126 bad sectors. - If your drive has a high number of bad sectors, you might need - to divide it into multiple FreeBSD slices each containing less - than 126 bad sectors. Stay away from low-level format programs - that mark <em>every</em> sector of a track as bad when - they find a flaw on the track. As you can imagine, the - 126 limit is quickly reached when the low-level format is done - this way. - - Second, if the slice contains the root filesystem, the slice - should be within the 1024 cylinder BIOS limit. During the - boot process the bad144 list is read using the BIOS and this - only succeeds when the list is within the 1024 cylinder limit. - <em>Note</em> that the restriction is not that only the root - <em>filesystem</em> must be within the 1024 cylinder limit, but - rather the entire <em>slice</em> that contains the root filesystem. - - - <sect3><heading>Kernel configuration</heading> - <p> - ESDI disks are handled by the same <it>wd</it>driver as - IDE and ST412 MFM disks. The <it>wd</it> driver should work - for all WD1003 compatible interfaces. - - Most hardware is jumperable for one of two different I/O - address ranges and IRQ lines. This allows you to have - two wd type controllers in one system. - - When your hardware allows non-standard strappings, you - can use these with FreeBSD as long as you enter the - correct info into the kernel config file. - An example from the kernel config file (they live in - <tt>/sys/i386/conf</tt> BTW). - -<tscreen><verb> -# First WD compatible controller -controller wdc0 at isa? port "IO_WD1" bio irq 14 vector wdintr -disk wd0 at wdc0 drive 0 -disk wd1 at wdc0 drive 1 - -# Second WD compatible controller -controller wdc1 at isa? port "IO_WD2" bio irq 15 vector wdintr -disk wd2 at wdc1 drive 0 -disk wd3 at wdc1 drive 1 -</verb></tscreen> - -<!-- - <sect3><heading>Tuning your ESDI kernel setup</heading> - <p> ---> - - <sect2><heading>Particulars on ESDI hardware</heading> - <p> - <sect3><heading>Adaptec 2320 controllers</heading> - <p> - I successfully installed FreeBSD onto a ESDI disk controlled by a - ACB-2320. No other operating system was present on the disk. - - To do so I low level formatted the disk using NEFMT.EXE - (<it>ftp</it>able from <it>www.adaptec.com</it>) and answered NO - to the question whether the disk should be formatted with a - spare sector on each track. The BIOS on the ACD-2320 was - disabled. I used the 'free configurable' option in the system - BIOS to allow the BIOS to boot it. - - Before using NEFMT.EXE I tried to format the disk using the - ACB-2320 BIOS builtin formatter. This proved to be a show stopper, - because it did not give me an option to disable spare sectoring. - With spare sectoring enabled the FreeBSD installation - process broke down on the bad144 run. - - Please check carefully which ACB-232xy variant you have. The - x is either 0 or 2, indicating a controller without or with - a floppy controller on board. - - The y is more interesting. It can either be a blank, - a "A-8" or a "D". A blank indicates a plain 10 Mbits/second - controller. An "A-8" indicates a 15 Mbits/second controller - capable of handling 52 sectors/track. - A "D" means a 15 Mbits/second controller that can also - handle drives with > 36 sectors/track (also 52 ?). - - All variations should be capable of using 1:1 interleaving. Use 1:1, - FreeBSD is fast enough to handle it. - - <sect3><heading>Western Digital WD1007 controllers</heading> - <p> - I successfully installed FreeBSD onto a ESDI disk controlled by a - WD1007 controller. To be precise, it was a WD1007-WA2. Other - variations of the WD1007 do exist. - - To get it to work, I had to disable the sector translation and - the WD1007's onboard BIOS. This implied I could not use - the low-level formatter built into this BIOS. Instead, I grabbed - WDFMT.EXE from www.wdc.com Running this formatted my drive - just fine. - - <sect3><heading>Ultrastor U14F controllers</heading> - <p> - According to multiple reports from the net, Ultrastor ESDI - boards work OK with FreeBSD. I lack any further info on - particular settings. - -<!-- - - <sect2><heading>Tracking down problems</heading> - <p> ---> - - <sect2><heading>Further reading<label id="esdi:further-reading"></> - <p> - If you intend to do some serious ESDI hacking, you might want to - have the official standard at hand: - - The latest ANSI X3T10 committee document is: - <itemize> -<item>Enhanced Small Device Interface (ESDI) [X3.170-1990/X3.170a-1991] - [X3T10/792D Rev 11] - </itemize> - On Usenet the newsgroup <htmlurl url="news:comp.periphs" - name="comp.periphs"> is a noteworthy place to look - for more info. - - The World Wide Web (WWW) also proves to be a very handy info source: - For info on Adaptec ESDI controllers see <htmlurl - url="http://www.adaptec.com/">. - For info on Western Digital controllers see <htmlurl - url="http://www.wdc.com/">. - - <sect2>Thanks to... - <p> - Andrew Gordon for sending me an Adaptec 2320 controller and ESDI disk - for testing. - |
