Please read this entire file before contacting us for help.

• Drive letters can be individually assigned.
• Improved performance in large long filename directories.
• Several minor bug fixes.

• README.TXT: This file
• NTFSDOS.EXE: DOS/Windows NTFS file-system driver
• NTFSHLP.VXD: Helper VxD needed only for long filename support in Windows 95

When NTFSDOS starts, it will scan all hard-disk partitions on your system to look for NTFS drives. It will mount all NTFS drives it finds as unique DOS logical drive letters, and will inform you as it does so.

If you run NTFSDOS under DOS 7.0, NTFS drives will support long filename calls even before Windows starts. To propagate this support into Windows 95, NTFSDOS automatically has Windows run the NTFSHLP.VXD VxD device driver. No changes to SYSTEM.INI or the registry are necessary for this to occur - NTFSDOS will detect when Windows 95 starts and load the driver without user-intervention. You need NTFSHLP.VXD only if you will be running NTFSDOS with Windows 95.

NTFSDOS implements its own caching, and uses one of two types of memory, depending on how your system is configured. Its first choice is to use XMS memory for caching, as this minimizes demands placed on conventional memory. If you start NTFSDOS before Windows, then HIMEM.SYS, which can be found in the WINDOWS directory under Windows 95 or the DOS directory under Windows 3.1, or its equivalent, must be started before NTFSDOS. If NTFSDOS does not detect an XMS erver, it will resort to allocating 64KB of conventional memory for ts cache. In either case, it will inform you of its action.

NTFSDOS takes five command line parameters. The /L parameter lets you specify which driver letters NTFSDOS should attempt to use as it mounts NTFS drives. The /C option lets you override the default XMS cache size. The /V option directs NTFSDOS to print some messages detailing the drives it looks at the memory it allocates. The /X switch forces NTFSDOS to use standard BIOS int 13 services. Use this if NTFSDOS has problems with your computer's extended int 13 services. Finally, the /N switch can be used to disable NTFSDOS support for compression. Much of the conventional memory that NTFSDOS normally uses is for compression buffers, so if you will be accessing drives or files that are not compressed and would like to optimize NTFSDOS use of memory, use this switch.

The syntax for these parameters is:

/C:<size>

/V

/X

/N

Specifies size of XMS cache in KB

Verbose

Disable extended int 13 support

Disable Support for Compression

There is no way to unload NTFSDOS from memory once it has started.

NTFSDOS does not recognize my NTFS drive

NTFSDOS does not handle cluster sizes > 4K on NT 4.0 formatted drives. This is rare, since NTFS compression does not handle these cluster sizes either.

NTFSDOS requires that disks be accessible via BIOS, using the INT 13 or extended INT 13 services. In some cases, SCSI drives may not be fully accessible without a DOS device driver (see your SCSI adapter documentation).

NTFSDOS uses too much conventional memory

Some people have complained that NTFSDOS is a memory hog. Unfortunately, this fact is largely imposed on us by the architecture of NTFS itself (sorry, but its a little more complicated than FAT, and much more memory intensive), coupled with our desire to provide reasonable performance across a wide variety of NTFS installations. In general, the footprint of NTFSDOS increases largely with the clustersize of the largest NTFS partition, and slightly with the number of NTFS volumes mounted.

Accessing an NTFSDOS drive causes a hang or crash

NTFSDOS does not support disk striping. Further, it cannot handle drives that are on partitions extending beyond the 2GB boundary, or that are larger than 2GB in size, UNLESS the computer's BIOS has extended INT 13 support for the drives in question. The latter restrictions are due to limitations in standard disk BIOS code that prevent it from addressing sectors 2GB or more from the start of a disk.

NTFSDOS has not been thoroughly bullet-proofed against corrupt NTFS drive data structures, so it may cause Windows to crash or hang when it runs into problems. To insure that a crash or hang is due to a problem with NTFSDOS rather than your NTFS drive, be sure to chkdsk the drive from Windows NT and try NTFSDOS again.

Starting programs or loading files seems very slow

Access of large compressed files may be noticeably slower than of their non-compressed versions.

File times are not correct when running under DOS 7.0 without Windows 95

This problem is due to the fact that NTFS and LFN FAT time stamps are stored in Coordinated Universal Time (UTC), which is based on Greenwich Mean Time, and Windows 95 automatically converts times stamps returned by LFN calls to local time. Since local time zone information is not accessible outside of Windows 95, running NTFSDOS under DOS 7.0 without Windows 95 results in the display of unadjusted times.

Programs complain about not being able to find files when they are there

A directory listing of files that have no short filename will result in the short filename field of the listing being blank. Changing the current directory to a path where any component of the pathname does not have a short filename will result in all short filename calls failing while in the directory. This makes most Windows 3.1 and DOS programs and many DOS commands (e.g. MORE) inoperative in these directories. However, LFN calls are supported in these directories.

Data read from a file appears to be corrupt

Since this work is based on reverse-engineering rather than official Microsoft specifications (which are reportedly available under special circumstances for large amounts of money), we do not guarantee data integrity of NTFSDOS drives. This is especially important if you are considering using NTFSDOS as a file backup utility.

Files or directories seem to be missing

Remember that files and directories that were created with no DOS 8.3 short filenames will not be visible if you are running DOS versions earlier than 7.0.

You get the message "No drive letter to mount NTFS partition..."

If NTFSDOS complains that it cannot mount a drive because there are no available drive letters, you must find the line in your CONFIG.SYS that begins with "LASTDRIVE=". If you do not find one, then add one. Set the LASTDRIVE variable to a letter that is greater, by the number of NTFS drives on your system, than the largest drive letter you normally have under DOS/Windows. For example, if the highest drive letter normally in use is E: and you have two NTFS drives, set LASTDRIVE to G: with a statement in CONFIG.SYS like:

LASTDRIVE=G:

If you still get the message then increment the letter and try again.

Remember to reboot after every change to CONFIG.SYS.

You get the message "Could not allocate XMS or conventional cache"

Memory usage on your machine is so high that NTFSDOS could not allocate 64KB for a conventional cache. Try removing unnecessary TSRs and drivers and/or running a DOS memory optimizer or manager.

XCOPY does not work in a DOS box

XCOPY will not work on NTFS drives that are mounted in DOS boxes under Windows 95 (e.g. running NTFSDOS in a DOS box). This is because you cannot run Windows programs off of non-global drives, and under Windows 5, XCOPY starts the Windows console program XCOPY32.EXE.

• disk types (IDE, etc.)
• disk and partition sizes
• BIOS version
• drive sizes and formats
• version of NT that was used to format NTFS drives
• version of NTFSDOS you are using
• an output dump of NTFSDOS run with the /V (verbose) option.
• version of DOS and/or Windows you are running NTFSDOS on

To provide long filename support (LFN), NTFSDOS hooks INT 21/AH=0x71 calls and implements LFN functionality when it sees an LFN call. Under Windows 95, NTFSHLP.VXD is required to send LFN calls down to the NTFSDOS for it to process; otherwise NTFSDOS would not see LFN calls since Windows assumes DOS redirected drives do not provide LFN support.

NTFSDOS also uses the INT 2F/11 and INT 13 APIs. Otherwise the magic is just memory and cache management plus interpretation of the NTFS on-disk structures.

If you have a dead system that you would like to recover data from or repair, and you have access to a second NT machine, you may want to try NTRecover, another utility we have written. A read-only NTRecover is available for free download, and with it you can access the drives on the dead system from the working system using native NT file systems and uiltities. In fact, to NT the drives appear as if they were local drives on the working system. With the read/write version, you can even chkdsk the dead system's drives.

Significant understanding of the NTFS file system layout was derived by studying the Linux-based NTFS driver code maintained by Martin von Loewis. We acknowledge his indirect contribution to this endeavor.

Andrew Schulman, et. al.'s, book, Undocumented DOS 2nd Edition (Addison-Wesley), was invaluable in providing network redirector information necessary for implementing NTFSDOS.