Subject: v03i057: dsptch, patches msdos 4.0 & 4.1 to fix bug
From: [email-masked]
Date: 13 Jun 89 03:00:15 GMT
Newsgroups: comp.binaries.ibm.pc

A problem was recently found in DOS versions 4.00 and 4.01 which can
cause FAT corruption when files that are larger than 32MB in size are
appended to. The bug is manifested if each and every of the following
occur:

1. BUFFERS (CONFIG.SYS command) are allocated with secondary cache
   enabled.
2. Greater than 32MB disk partition is in effect.
3. The user is sequentially accessing a file and any part of that file
   falls within the range of 32MB to 32MB + 10K on the disk, and the
   portion of the file being accessed falls between that same narrow
   range.
4. Immediately after sequentially accessing this file, the user
   performs an operation that causes the system to read a FAT (file
   allocation table) sector.

If all of these conditions are true, the result is a corruption of the
FAT (and loss of data). The chance of all of the above occuring in the
sequence described is remote.

Microsoft has provided a patch utility that corrects this problem.  The
name of the utility is PATCH.EXE. A description file, READ.ME, is
included to provide instruction on how to use the PATCH.EXE program.
These two files have been archived into the archived file DSPTCH.ARC.
This archive is available on various computer bulletin boards and
information services, such as Microsoft OnLine and Compuserve. [And now
probably Simtel20, if Keith Peterson sees this...]

The patch, has a /F switch (ala CHKDSK), which will allow the actual
patch to occur. Otherwise, it will not modify the DOS system file. If
this switch is not used, PATCH.EXE will examine the boot disk and
determine if the system needs to be patched. The system should be
rebooted after the patch occurs.

See the file READ.ME for further information.
--
Lee Fisher, [email-masked], [email-masked]
{uw-beaver,decvax,decwrl,intelca,sun,tikal,uunet}!microsoft!leefi