System Clock Speeds Up When Using Task Swapper (77246)
The information in this article applies to:
- Microsoft MS-DOS operating system 5.0
- Microsoft MS-DOS operating system 5.0a
- Microsoft MS-DOS operating system 6.0
This article was previously published under Q77246 SYMPTOMS
Your system's time and date increment at an unusually fast rate when
Task Swapper is used. Your real-time clock is not affected, and
rebooting the system sets the time and date back to their correct
values.
CAUSE
The Task Swapper in MS-DOS Shell can cause the system clock to speed
up on systems where the speaker port (61H) is not properly initialized
to an "off" state.
WORKAROUND
Task Swapper has code to manage programs that reprogram the
timer. This code is dependent upon the value returned by the speaker
port (61H). In particular, the lower two bits of this port (bits 0
and 1) control the speaker. When the computer is first turned on,
both of these bits should be cleared (zeroed) to indicate the speaker
is off. If your computer's hardware does not properly initialize the
speaker port, you can use the MS-DOS Debug utility to create a program
that will. Follow the instructions below to create SPKROFF.COM.
- At the command prompt, start Debug by typing the following command
and pressing ENTER:
- Enter the Debug commands as outlined below:
Debug Command
Prompts to Enter Comments
------- -------- --------
- a 100 Assemble beginning at CS:0100
nnnn:0100 in ax,61 Read port 61H into AX register
nnnn:0102 and al,fc Clear bits 0 and 1 - leave rest alone
nnnn:0104 out 61,al Write new value to port 61H
nnnn:0106 int 20 Call DOS int 20H - terminate program
nnnn:0108 <ENTER> Press ENTER to end assemble process
- n spkroff.com Name file SPKROFF.COM
- rcx Replace CX register
CX 0000
: 0008 Place 0008 into CX register
- w Write file
Writing 00008 bytes
- q Quit DEBUG
Each time you reboot your computer you should execute SPKROFF.COM
before starting Shell. It may work best to execute SPKROFF.COM from
your AUTOEXEC.BAT file. If you load Shell from AUTOEXEC.BAT, be sure
to place the line that executes SPKROFF.COM before the line that
executes Shell.
Modification Type: | Major | Last Reviewed: | 10/10/2003 |
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Keywords: | KB77246 |
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