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FIXRB.DOC
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Text File
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1987-11-22
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4KB
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67 lines
FIXRB.DOC -- Fix Rainbow IO.SYS Bug
THE PROBLEM
The DEC Rainbow MS-DOS system has a bug which garbles writing to
the console in "raw" mode. Most software does not use raw mode, so
most users are not affected by the problem. It is likely to affect
software which is both DOS-generic and screen-writing intensive. Raw
mode is a good choice for such software because it provides much more
screen speed than normal DOS writing, without the machine-dependency of
direct memory access or interrupts. Raw mode also prevents ^C, ^S and ^P
from adversely affecting a program.
The bug in will make the first letter of each string repeat for the
length of the string. For example, if the string "DEC Rainbow" were
written to the console, you would see "DDDDDDDDDDD". The file TEST.EXE
included with this descripition tests normal console writing and raw
mode writing, and can be use to verify the problem and the fix.
THE SOLUTION
There is a known patch for this bug, which involves switching two
bytes in the MS-DOS system file IO.SYS. The program FIXRB makes this
patch automatically for MS-DOS versions 2.05, 2.11, 2.11-1 and 3.10.17.
Other versions of 3.10 may also be correctly patched, but we have not
tested them. There is no harm done by making this patch, even if the
bug is not causing any problems right now.
To make the patch, set the default drive to the drive containing the
disk from which you boot up your system. The disk to be patched must NOT
have a write-protect tab. Then run FIXRB. For example, if drive A:
contains the disk from which you normally boot the system and B: contains
a disk with FIXRB.EXE, you would type the following two DOS commands:
A:
B:FIXRB
The program will display which version of DOS you are running and will
give messages to indicate when it has completed the patch. The patch
will not take effect until the next time you boot MS-DOS to this disk.
If you boot to different disks at different times, the patch must be
made to each of them.
If the file has already been patched, if the version of DOS
currently running is different from the version of IO.SYS, or if
there is no IO.SYS on the default drive, this information is reported.
The FIXRB patch can be undone by running the SYS command from an
MS-DOS system disk which has NOT had FIXRB run on it. Although we know
of no reason for wanting to undo this patch, it is always prudent to
keep one unmodified MS-DOS boot disk (for example, your original
MS-DOS distribution disk).
WHO, WHY, HOW, WHEN
FIXRB was written by Willett Kempton, Visible Software, using
information provided by FinalWord (via Michael MacMillan). It is
written in Standard Pascal with DOS extensions of ProPascal ver 3.1.
ProPascal is a high-powered optimizing Pascal compiler which greatly
facilitates DOS system accesses from Pascal. FIXRB was written because
we needed to make our product, Dr. Pascal version 2.0, run correctly on
the DEC Rainbow. Dr. Pascal is a program development system which
facilitates writing, debugging, and understanding execution of Pascal
programs (most of our sales are for IBM-PC clones, but the Rainbow is
our development environment of choice.)
This version of FIXRB was finalized on 22 November 1987. The first
version, of 4 November 1987, was identical but could not patch MS-DOS
3.10.17. FIXRB is donated to the public domain by Willett Kempton. This
program and documentation are provided "as is", without any warranty.