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fdformat - Set of floppy utilities including xformat.exe - Format Floppy Disks with Higher Capacity

This project is of historic interest only.
Christoph Hochstätter worked on it between 1988 and 1991.
It is written in Turbo Pascal and x86 Assembly.
It runs under MS-DOS/PC-DOS 3.20 or higher and also Windows 95/98/98SE/ME.

IBM or compatible Computer
DOS 3.20 or above
4.77Mhz. 8088

FDFORMAT is a replacement for the DOS-Format program, which has thefollowing advantages:

1. Supporting 3½"-1.44 MB drives with any BIOS-Versions in ATs andClones. This saves you a lot of money, you would need for a newBIOS-Version.
2. Formatting and using of 720/820 kByte disks in AT 5¼"-1.2 MByteDrives using cheap double-density (DD) disks.
3. Increasing the capacity of your disks up to 300 kByte additionalstorage.
4. Supporting 3½"-360 kByte format. This is useful, when you want tomake copies of 5¼"-disks to 3½"-Disks using DISKCOPY
5. Enhance speed of your diskette I/O up to 100% with sector sliding.This is a method of physical ordering sectors in a way, that yourdrive is ready to read the next logical sector, when your headadvances one track.
6. Improved BOOT-Sector, which automatically boots from harddisk, ifthe diskette in drive A: is not a system disk. This allows you toleave the diskette in drive A:, when you reboot the system.

To make full use of FDFORMAT, you have to make a small TSR resident inmemory. There are two different TSRs for XT-computers and AT-computers. 80386/80486 machines are treated as AT computers here. TheTSR for AT computers is FDREAD.EXE and for XT computers it isFDR88.EXE. Both TSRs use less than 200 Bytes resident memory.

To make FDREAD (or FDR88) resident simply type FDREAD (or FDR88) fromthe DOS-Command-Line. Or install it in your AUTOEXEC.BAT file. If youhave a memory-manager installed, that supports UMB (like QEMM, QRAM,mov'em or 386-Max), do not load FDREAD (or FDR88) high. The TSRautomatically detects the memory manager and will load high itself.

FDREAD will also automatically load high on computers with a 286(!!!)processor and up, if DOS 5 or higher is used. You must have HIMEM.SYS(or another XMS-Driver) installed and put DOS=HIGH in your CONFIG.SYSfile. Since this technique of high-loading is quite tricky, you mustensure, that FDREAD is loaded before any program that plays with theA20 line and grabs the Interrupt 13 (Hex). This is the case for somedisk-caching programs like HYPERDISK(TM). If you are using a disk-caching program, load FDREAD before the caching program. Also, if thesystem hangs, after you installed FDREAD, load FDREAD as the firstTSR.

If you get the error "Too much memory available". You must load FDREADtwice to avoid this error.

The TSR is required to support diskette formats, which are non-standard under DOS. If you intend to use FDFORMAT only with DOS-standard-diskette-formats, you do not need FDREAD (or FDR88).

Note, that it is not possible to create bootable diskettes, whichrequire the TSR. It may also be possible, that a format, which can beread without the TSR on your computer, will fail on another computer.If you are creating bootable diskettes, it is recommended only to useDOS-standard-formats.

The general Syntax for FDFORMAT is:

             FDFORMAT <drive> [options]

may be A: or B:. FDFORMAT does not format harddisks. Optionsbegin with a letter or number. Options may be preceeded by '/' or '-'.If you do not preceed options with '/' or '-', you must seperate theoptions with spaces. '.' and ':' are always ignored. So the followingcommands will all format a 1.44 MByte Disk in Drive A:

 FDFORMAT A: /F:1.44 FDFORMAT A: -F144 FDFORMAT A: F144

You may precede all numbers with a $-sign to indicate, that they arehexadecimal numbers.

The most important option is the F-Option. The F-Option determines thegeneral Format, which is used for the target diskette.

The following table shows, which parameters are allowed for the F-Options and for which type of Disk-Drive:

F-Opt Format          360k-Drive 720k-Drive 1.2M-Drive 1.44M-Drive----- --------------- ---------- ---------- ---------- -----------F160  160 kByte Disk  yes        FDREAD     yes        FDREADF180  180 kByte Disk  yes        FDREAD     yes        FDREADF200  200 kByte Disk  FDREAD     FDREAD     FDREAD     FDREADF205  205 kByte Disk  FDREAD     FDREAD     FDREAD     FDREADF320  320 kByte Disk  yes        FDREAD     yes        FDREADF360  360 kByte Disk  yes        FDREAD     yes        FDREADF400  400 kByte Disk  FDREAD     FDREAD     FDREAD     FDREADF410  410 kByte Disk  FDREAD     FDREAD     FDREAD     FDREADF720  720 kByte Disk  no         yes        FDREAD     yesF800  800 kByte Disk  no         FDREAD     FDREAD     FDREADF820  820 kByte Disk  no         FDREAD     FDREAD     FDREADF120  1.2 MByte Disk  no         no         yes        yesF12   1.2 MByte Disk  no         no         yes        yesF144  1.44 MByte Disk no         no         FDREAD     yesF14   1.44 MByte Disk no         no         FDREAD     yesF148  1.48 MByte Disk no         no         FDREAD     yesF16   1.6 MByte Disk  no         no         no         FDREADF164  1.64 MByte Disk no         no         no         FDREADF168  1.68 MByte Disk no         no         no         FDREADF172  1.72 MByte Disk no         no         no         FDREAD

FDREAD in the above table means, that this format will work only, ifFDREAD (or FDR88) is installed. You may find out, that this table willnot be valid for your table and that you can use certain disketteformats without FDREAD (or FDR88), that are listed to work with FDREAD(or FDR88) only.

The other options are:

    1    : Format single sided Disk (provided for DOS-FORMAT           compatibility).    4    : Format Standard 360 kByte Disk (provided for DOS-FORMAT           compatibility).    8    : Format 8 sector Disk (provided for DOS-FORMAT compatibility).    A    : Use BIOS-Calls only to switch to different diskette types.    Bnnn : Use Disk-Type Byte nnn (for use with older BIOS Versions).    Cnnn : Use nnn Sectors per Cluster (nnn = 1 or 2).    Dnnn : Use nnn Root-Directory-Entries (nnn = 1-224).    Gnnn : Use Gap-Length of nnn (for use by experts only).    Hnnn : Use nnn heads (nnn = 1 or 2).    Innn : Use an Interleave of nnn (for use by experts only).    K    : Do not wait for any keyboard input, when starting FDFORMAT.           (Useful, when starting FDFORMAT from batch files).    Mnnn : Use Media Byte nnn (Useful for ATARI formats).    Mnnn : Use Media-Descriptor-Byte nnn. (Useful when formatting ATARI ST           disks).    Nnnn : Use nnn Sectors.    O    : Format 720 kByte disk for use with AT&T/Olivetti M24/M28.    Q    : Quick Format. Only rewrite the System-Area.    R    : Do not verify disk (and save 33% time).    S    : Make System-Disk.    Snnn : Use nnn Sectors.    Tnnn : Use nnn Tracks.    U    : Unconditionally format the diskette.    V    : Write Label to Disk.    W    : Format with erase. Physically reformat diskette without data           loss    Xnnn : Slide nnn Sectors, when head changes.    Ynnn : Slide nnn Sectors nnn, when track changes.

Examples:

    FDFORMAT A: /4                                    (format 360 kB disk)    FDFORMAT A: /F:1.72                              (format 1.72 MB disk)    FDFORMAT A: /T:80 /N:9                            (format 720 kB disk)    FDFORMAT A: /O                    (format 720 kB disk for AT&T M24/28)    FDFORMAT A: /F:720 M$F7 B$54         (format 720 kB disk for ATARI ST)    FDFORMAT A: /F:12 D64                (format 1.2 MB disk with 64 RDEs)    FDFORMAT A: /F:410 R               (format 410 kB Disk without verify)

Beginning with version 1.8. FDFORMAT formats disks the same way asDOS-FORMAT of DOS Version 5. If the Q and U options are not specified,FDFORMAT checks, if the diskette is already formatted in the formatyou have choosen. If this is true, FDFORMAT only verifies the disk andrewrites the System-Area. If the disk is formatted in another format,a real low-level formatting is performed. If you specify the U option,the diskette will be low-level formatted in any case.

The Q option specifies a quick format. FDFORMAT tries to determine thecurrent diskette format and then only rewrites the system area. Alloptions to specify a different format are ignored, if you specify theQ option. FDFORMAT will also skip verifying, if the Q option isselected. If the Q option is selected and FDFORMAT cannot find a validboot sector, the diskette will be low-level formatted with the formatyou specified.

This option tells FDFORMAT, how many tracks are to be used. A Standard360 kB diskette has 40 tracks, all other standard formats have 80tracks. You can set this option to 1-41 for an 360 kB drive and to 1-82 for all other drives. The more tracks you use, the more storage youwill receive. Some drives allow even more than 41 or 82 tracks, butyou may have trouble, when trying to read this diskette on anotherdisk drive. The default is 40 for a 360 kB Drive and 80 for all otherdrives.

Example: FDFORMAT A: /T:41 (format a disk with 41 Tracks. This willgive you 369 kB storage in a 360 kB drive)

This option determines the number of sectors per track you will use.The standard and default values for the different formats are:

    disk format standard value maximum value possible    ----------- -------------- ----------------------    360 kB            9                  10    720 kB            9                  10    1.2 MB           15                  18    1.44 MB          18                  21

You may use this option to increase the storage of your diskette too.

Example: FDFORMAT A: /N:10 (format a disk with 10 sectors. This givesyou 400 kB storage in a 360 kB drive).

You can set this option to 1 or 2. The default is always 2. Normallyyou do not need this option, since single-sided disks are rarely used.

These three options determine your diskette storage. The formula forthe diskette storage is:

                  tracks * sectors * sides  storage in kB = ------------------------                              2

Since diskettes use usually 2 sided, you can simplify this formula to:

  storage in kB = tracks * sectors

Examples:

          FORMAT A: /T:80 /N:9 /H:2 (format a 720 kB disk)          FORMAT A: /T:82 /N:10 /H:2 (format a 820 kB disk)          FORMAT A: /T:40 /N:9 /H:2 (format a 360 kB disk)          FORMAT A: /T:41 /N:10 /H:2 (format a 410 kB disk)

You can use the F-Option (described above) as a shortcut for the T, Hand N options (eg. FORMAT A: /F:1.44 is equal to FORMAT A: /T:80 /N:18/H:2).

Note: Always use High-Density-Diskettes when you format with more than11 sectors/track and always use double-density-disks, when you formatwith 10 sectors and below.

Look at the following table to see, which values are maximum for T, Hand N.

    Drive and disk                  max T  max N  max H Storage    ------------------------------  -----  -----  ----- -------    360 kB drive with DD-diskette    41     10      2    410 kB    720 kB drive with DD-diskette    82     10      2    820 kB    1.2 MB drive with DD-diskette    82     10      2    820 kB    1.2 MB drive with HD-diskette    82     18      2   1.48 MB    1.44 MB drive with DD-diskette   82     10      2    820 kB    1.44 MB drive with DD-diskette   82     21      2   1.72 MB

A cluster is the minimum allocation unit DOS can handle. DOS supports1 or 2 sectors per cluster for floppy disks. If you specify /C:1 spaceis allocated in 512 Bytes steps. /C:2 means that space is allocated in1024 Byte steps. You can optimize your disk organization, if you use/C:1, when you plan to store "many small" files and specify /C:2, whenyou plan to store "few large" files on the disk to be formatted. Thedefault is /C:1 for high density disks and /C:2 for double densitydisks

Example: FORMAT A: /F:360 /C:1 (format a 360 kB disk with 1 sectorper cluster)

Note: A blank formatted disk with /C:2 always has more bytes free thanwith /C:1. But when files are stored to the disk, your disk space willbe handled more dynamically.

This option determines the number of Root-Directory-Entries. Thedefault is 112 for double density disks and 224 for high densitydisks. This value can be reduced to get additional space on disk orincreased up to 240 to reserve for space for files in the rootdirectory. This option does not affect any of your subdirectories.Subdirectories are dynamically allocated. You only have to determinethe size of root directory. Legal values for disks with 1 sector percluster are 16, 32, 48, .... and for disks with 2 sectors per cluster16, 48, 80, .... if you specify a value between two legal values, itwill be increased to next legal valueautomatically.

Example: You need a disk that will not have more than 40 files in theroot directory. So type: FDFORMAT A: /D:40. You will get a disk with48 root directory entries and you have more space for data.

This option is actually a shortcut for /T:80 /N:9 /H:2 /D:144. TheAT&T and Olivetti M24/M28 Computers use 720 kB Disks with 144 rootdirectory entries. The standard IBM 720 kB format has 112 rootdirectory entries. So simply use the /O option to format a diskette ina 5¼"-1.2 MB drive or a 5¼"-720 kB drive.

Example: FDFORMAT A: /O

Note: If you could not read M24/M28 720 kB disks in your 1.2 MBdrive until now, try again with FDREAD installed. It will workfine.

FDFORMAT uses the same media descriptor byte as DOS-Format would do.If you override this value, this has no effect under DOS 3.3x or DOS4.0x. But you may not be able to read the disk under DOS 3.2x. Thisoption was added to support to format disks for the ATARI ST. Refer tothe ATARI Documentation to set the correct Values for the mediadescriptor and track, heads, sectors.

The R option skips verifying each track after it has been formatted.This saves 33%-50% of time during formatting a diskette. Thedisadvantage is that errors on the diskette are not detected. Atypical example for missing error detection is typing FDFORMAT A: /Rin an 1.2 MB drive with a double density disk inserted. FDFORMAT willnot report any errors in this case. If you are sure that you have agood diskette and you specified no wrong parameters, the /R option isa good choice to save time.

The K option suppresses the message "Insert new disk in drive...." andstarts formatting immediately, after FDFORMAT is started. This isuseful, if you want to start FDFORMAT from a batch file or an externalprogram. You can also suppress any screen output, if you add ">NUL" tothe FDFORMAT command (See your DOS Manual for piping input andoutput). FDFORMAT returns an exit code or errorlevel, which can beused in batch files. The exit codes are:

Exit Code Meaning--------- ----------------------------------------------------  0       normal completion  1       syntax error or illegal parameters  2       specified drive cannot be formatted  3       cannot determine format for format without erase  4       aborted by user (after I/O error or by Ctrl-Break)  8       I/O error for config file 16       syntax error or illegal parameters in config file 32       error writing disk label128       incorrect DOS version (< 3.20)

The S option lets you format a system disk. It copies boot-sector,DOS-System-file and COMMAND.COM to your disk. FDFORMAT does not dothese task by itself, but calls the DOS-Command SYS to do so. Thus youmust make sure, that SYS.COM or SYS.EXE is in a directory, which isincluded in your PATH Environment Variable. The call to SYS is made toensure compatibility with any DOS Version.

Note: You cannot create a system disk, which cannot be read withoutFDREAD.

Example: FDFORMAT A: /F:360 /S (correct)         FDFORMAT A: /F:410 /S (incorrect, because this                                format requires FDREAD)

This is the same as the /H:1 option. provided for syntax compatibilitywith DOS-Format.

This is the same as the /S:8 option. provided for syntax compatibilitywith DOS-Format.

This is the same as the /F:360 option. provided for syntaxcompatibility with DOS-Format.

This option does really nothing in FDFORMAT Versions above 1.2. It wasprovided for compatibility with earlier versions.

This option writes a volume label to your disk. You may specify simply/V. This will prompt you for a volume label. You may also specify/V:. This will write the name to your disk.

Example: FDFORMAT A: /F:820 /V (prompts for volume label)FDFORMAT A: /V:mydisk (Writes volume label MYDISK)

These options can be used to enhance the performance of your disk upto 100%. This is a bit difficult to explain. Imagine a standard 360 kBdisk. It has 9 sectors on each track numbered 1 to 9. Normally thesectors on all tracks ordered "1 2 3 4 5 6 7 8 9". With sector slidingof 1 you order "1 2 3 4 5 6 7 8 9" on track 0, "9 1 2 3 4 5 6 7 8" ontrack 1, "8 9 1 2 3 4 5 6 7" of track 2 and so on.

You can easily imagine, that it takes a little time, when yourdiskette drive head steps from one track to another. But your diskettecontinues rotating. Without sector sliding your diskette is positionedto sector 2 or 3 on the next track, when the stepping is done. Itneeds nearly a full revolution until sector 1 of the next track can beread. With sector sliding of 1 or 2 your diskette is positionedexactly on sector 1, when it starts reading again.

The DOS-Format program always formats with sector sliding 0. FDFORMATprovides two parameters to do sector sliding. /Xn slides n sectors,when you change the head, but not the track. /Ym slides m sectors,when you change the track. Normally only /Y is useful, but on somesystems, especially XTs, you can reach additional speed by using /X.

Now, how to determine the correct value for sector sliding. In generalyou can say good values for /X are 0-2 and for /Y 0-4. The default is0 for /X and /Y. You to experiment with your configuration, whichvalue is optimal for you. You may reconfigure your default sectorsliding in the FDFORMAT.CFG file (described later). You have to findout this for each format seperately. Always good choices are thefollowing:

Disk-Size          Good choice for sector sliding------------------ ------------------------------320-410 kB              /X:1 /Y:3720-820 kB              /X:1 /Y:21.2 MB-1.72 MB          /X:2 /Y:3

This will improve your diskette perfomance 50%-100% on almost anysystem.

Example: FDFORMAT A: /4 /X:1 /Y:2 /R/K/V:SLIDE_DISK

This option is used to reformat a diskette. This is useful, when youhave diskette, that is still readable, but only with several retries.This is often the case, if you try to read a 360 kB Diskette in a 360kB drive, that was written in an 1.2 MB drive.

If you choose this option, no modifications are made to diskette. Ifyou e.g. specify a different format or volume label, these options areignored. The diskette will be read in track by track. Then the trackwill be reformatted and the data is written back to the diskette.

It is safe to press Ctrl-Break during format without erase, becausethe exit-request is notified, when you press Ctrl-Break, butperformed, when the current track is completely written.

This option tells FDFORMAT to use only BIOS-Calls to change thediskette type and not to write the Media Byte directly. This option isrequired on most XT-Systems with HD-Controllers and external diskettedrives. It has the typical disadvantage, that some BIOS Versions donot support every Media Type in every drive. So use this option only,if you encounter problems without it. This option is also configurablein the FDFORMAT.CFG file descrived later.

The I option changes the Interleave factor for diskette format.Normally the best interleave is 1, thus it takes only 1 revolution toread an entire track. But there are 2 exceptions to it. Whenformatting a 21 sector 3½"-HD disk or a 18 sector 5¼"-HD disk. Youneed an interleave of 2 in these cases, because a data sector is usedas GAP. If you do not use an interleave of at least 2, the disk willbecome unreadable.

But you do not have to take care about this option, FDFORMATautomatically determines the best interleave for you (1 or 2). Howeveryou can set your interleave whatever you like, but the only effect is,that your disk becomes slower.

Example: FDFORMAT A: /I:6 (format a very slow disk)

The GAP length is the fill space between two sectors on one track. Aswith the Interleave, FDFORMAT determines the best value for you. Youcan reduce the GAP length to speed up your diskette. But this reducesyour safety, when storing data, unless you choose an interleave of 2.And an interleave of drastically slows down your disk performance. Ifyou want to reduce your GAP length anyway, do not set it below 32 forhigh density disks and not below 40 for double density disks.

For the safety of your data, it is recommended not to modify the GAPlength. Sector sliding is a better method to speed up your disketteperformance and does not affect the safety of your data.

The Bnnn option - Setting the disk type Byte

This option affects to 80286/80386/80486 Computers only and needs tobe set, if you have an incompatible or older BIOS, which does notsupport 1.44 MByte Drives. It is configurable in the FDFORMAT.CFG filedescribed later. This byte is made out of the following components:

Group Decimal Hexadecimal  Meaning-----------------------------------------------------------------         0         0       Media Type unknown 1      16        10       Media Type known-----------------------------------------------------------------        32        20       double stepping (40 Tracks) 2       0         0       single stepping (80 Tracks)-----------------------------------------------------------------         0         0       Data-Transfer-Rate: 500 kBaud        64        40       Data-Transfer-Rate: 300 kBaud 3     128        80       Data-Transfer-Rate: 250 kBaud-----------------------------------------------------------------         0         0       360 kB Disk in 360 kB Drive, unchecked         1         1       360 kB Disk in 1.2 MB Drive, unchecked         2         2       1.2 MB Disk in 1.2 MB Drive, unchecked         3         3       360 kB Disk in 360 kB Drive, checked         4         4       360 kB Disk in 1.2 MB Drive, checked         5         5       1.2 MB Disk in 1.2 MB Drive, checked 4       7         7       state not defined (3½"-Drive)-----------------------------------------------------------------

To get the correct value for your format, select one Value out of eachgroup and add these values. Normally the media type byte is setcorrectly, following these rules:

Group 1: Always set to 16Group 2: 32, if tracks from 1-43, else 0Group 3: high density disks: always 0 double density disks: 64 for         5¼"-Disks, 128 for 3½"-DisksGroup 4: always set to 3

Why set group 4 always to 3? There is a problem with DTK-BIOS. DTK-BIOS seems not to work with any other value than 3. All other BIOSVersions I have tested, seem to ignore the Value of Group 4. So itwill be the best choice to set it always to 3. In some few cases. YourSystem will not work with the default value. In this case, try out anyvalue from 0-7 for Group 4. It should work with at least one value. Ifyou have determined the correct value, you can write it in theFDFORMAT.CFG file.

Before you start setting up a configuration file, you should try, ifall formats will work correctly. FDFORMAT normally automaticallydetermines the best options for you. If something seems to fail, thenset up a configuration file.

You must also create a configuration file, if you have one of thefollowing situations.

1. You have an XT with a high density controller to support 1.2 MByteor 1.44 MByte drives.
2. You have an AT and an 1.44 MByte drive, but you cannot install itwith your setup program (e.g. IBM/Advanced diagnostics).
3. You have an XT (like EPSON QX-16 or AT&T/Olivetti M24/M28), whichhas one or more 720 kByte drives, that also supports 360 kBytediskettes.
4. You have a 5¼"-720 kByte drive in an AT.

The general format for FDFORMAT.CFG is:

: [XT|AT] [BIOS] [40=n] [80=n] [F=n] [360=n] [720=n] [1.2=n][1.44=n] [X=n] [Y=n]

Example for a configuration file:

REM Configure drive B: for 1.44 MByteB: AT BIOS F=7 360=$B7 720=$97 1.44=$17 X=2 Y=2

REM Configure drive A: for 5¼"-720 kByteA: AT F=2 BIOS 720=$54 X=0 Y=0REM All Numbers preceded by a $-sign are hexadecimal

The options in detail:

XT : Tell FDFORMAT that your Computer is an XT or compatible anddoes not perform any AT-BIOS functions. This option is onlyneeded, if FDFORMAT does not automatically recognizes, thatyour computer is an XT. This option is also needed, if your XTsupports 720 kByte drives, that can handle 360 kByte diskettestoo.

AT : Tell FDFORMAT that your Computer is an 80286/386 or 80486Computer or an XT, that supports AT-BIOS functions. This optionis only needed, if FDFORMAT does not recognize, that you canuse AT-BIOS functions. A typical case, where you need thisparameter is, when you have an XT with a high densitycontroller installed.

BIOS : This option works only with AT-like-BIOS. It tells FDFORMAT notto modify the disk type byte directly, as it is the default,but try to change the format information via BIOS-Calls. Thisoption should only be used, if FDFORMAT does not work withoutthis option. The BIOS option has the typical disadvantage thatsome BIOS-Versions do not support all formats for all drives.In this case you must set the disk type byte for theunsupported format in your configuration file. This option isdescribed later.

40 : This option works only with a few XT-BIOS-Versions for 720kByte drives. You can specify an offset to the physical drivenumber, that indicates, that a 40 Track Diskette (360 kByte) isinserted, when calling BIOS-Disk I/O. Normally this option isset to 0.

80 : This option works with most XT-BIOS-Versions, that support 720kByte Drives, who also can handle 360 kByte diskettes. Theseare for example AT&T M24/M28 or EPSON-QX16. The most often usedoffset is 64. Try 64 first, if it does not work try 32, 16, 8,4 or 2. Do not try any other values, it will not work.

F : This option needs to be set only, if your BIOS does not supportthe your type of disk drive. You need this option, if you havean 1.44 MB drive installed and your BIOS does not support it.If you want to install this option use the following values:F=0 for 360 kByte Drive, F=1 for 1.2 MB drive, F=3 for 720 kBDrive and F=7 for 1.44 MB drive.

360 : Use this option to use another disk type byte for 360 kBdiskettes than the default value of $73. If you have set theBIOS option, the 360 kByte format will not be set by BIOS, butdirectly using this disk type byte. Refer to the B command lineoption to see how you can determine the correct disk type byte.

720 : same as 360, but for 720 kB format.1.2 : same as 360, but for 1.2 MB format.1.44 : same as 360, but for 1.44 MB format.

X : can be used to override the default of 0 for sector sliding,when the head changes.Y : can be used to override the default of 0 for sector sliding,when the track changes.

A: XT PC80=64               720 kB drive in XT like AT&T M24A: AT F=7                   1.44 MB drive in AT or XTA: AT F=1                   1.2 MB drive in AT or XTA: AT F=2 360=$74 720=$57   720 kB 5¼"-Drive in ATA: AT F=2 360=$73 720=$53   720 kB 5¼"-Drive in AT & DTK-BIOS

Special thanks to the following people:

Christoph Hochstätter: The original Author

Jochen Roderburg: For suggestions and improvements to supportcompatibility with several BIOS-Versions.

Michael Ho: For an improvement in sector sliding.

Joel Armengaud: For supporting automatic detection of 720 kBytediskettes in FDREAD.

Jörg-Stefan Sell: For supporting an interface routine to lesscompatible XT computers.

Michael D. Lawler: For lots of suggestions of improvemnts.

Peter Summers: For an improvement in FDREAD/FDR88