AT-SLOW Demo Version
Version 4.00 Unregistered
PC-AT High Performance Slowdown
By David Keil
This is a demo version of AT-SLOW. It has all the features of the
registered version to give you an idea of how it works but is limited
to aprox 5min of operation.
Send for your registered version of AT-SLOW today by using the
registeration form at the end of this doc file.
AT-SLOW is a utility which when loaded will use the high
resolution timer found in a PC-AT or close clone, to slowdown
games and other programs which run to fast on PC-AT's.
This program is hardware dependent and requires a PC-AT or
close clone and a 80286/80386/80486 processor to operate. AT-SLOW
uses the AT's real time clock found at interrupt 70h to slowdown the
Using the real time clock's interrupt has two advantages
over the usual use of the normal PC's timer.
1 - The high resolution timer can occur up to 8192 times a second
(as opposed to 18.2 with the normal timer). This provides a much
smoother slowdown than with the normal timer. This also
provides a higher degree of performance reduction.
2 - Since this slowdown uses interrupt 70h and only AT's use
this interrupt, programs don't know to re-vector it. So
programs that don't work with normal slowdown programs
will work with AT-SLOW.
Version 4.00 contains several enhancements and additions that
were not available in the previous shareware version.
1 - Friendlier user interface.
2 - Option to remove program from memory.
3 - Optional 1024, 2048 & 4096 int's/second for slower AT machines and
for slowing 80486 machines down to 80386 speeds.
4 - Standby mode which lets the computer run at full speed until the
delay is wanted. Then it can be activated by a sequence of
5 - Hot-key enabling, disabling & changing of the delay value while in
the program you want delayed
6 - Hot-key to DOS function for older programs that don't allow an
easy exit to DOS.
7 - New CPU option allowing you to enter a CPU clock speed you want the
the system to run at.
The command for using AT-SLOW is
/t = ???? is amount to slowdown PC-AT. Valid range is 0-1999.
/c = ?? is CPU speed in MHZ wanted. Valid range is 2-99.
/z = Tell AT-SLOW the processor is a 80486 for CPU calabration.
/s = Put AT-SLOW in standby mode.
/1 = Use 1024 INT's/second.
/2 = Use 2048 INT's/second.
/4 = Use 4096 INT's/second.
/8 = Use 8192 INT's/second. (Default value)
/d = Disable slowdown.
/e = Enable slowdown.
/r = Remove program from memory.
/h = Show this help screen.
/? = Show current program settings.
The range of values for delay is 1-1999. Values of 20-60
on 286 machines is usually adequate. As the delay value is increased
there will come a point when the computer actually is to slow to
function. If this happens use the hot-keys to disable the delay and
then try a smaller value or use the /c option.
The range of values for the CPU command are 2-99 mhz. This command
is used instead of the /t command.
The CPU command will compute the correct delay value to give the
speed requested. The message:
'CPU delay being calabrated, please wait!' will be displayed during
which time the system will appear to to locked up.
When finished if it was possible to give the requested CPU speed the
message: 'CPU set to speed requested.' will be displayed.
If the speed selected is to fast or slow to be achieved then the message:
'Unable to set CPU to speed requested, delay disabled!' is displayed.
Possible reasons the speed could not be set are:
1 - speed higher then real CPU speed. (buy faster machine)
2 - Speed higher then possible with ints/sec selected.
(select a lower number of ints/sec)
3 - Speed lower then possible with ints/sec selected.
(select a higher number of ints/sec)
1 IT MAY TAKE AS LONG A 1MIN TO CALABRATE SPEED.
2 This function is used to help compute a delay value required for a
particular program. Once the speed has been computed and fine tuned
(using the hot-keys) the delay value should be determined using the
/? option and that value used with the /t option. This will
eliminate the calabration delay.
3 A valid /t or /c command must be given before the program will
Using AT-SLOW continued:
/z Tell AT-SLOW that the processor is a 80486 so the /c option will
calabrate the system speed correctly. Include this option each time you
use the /c option on a 80486 computer.
EX. AT-SLOW /c50/z (slow down a 80486 to the speed of a 80386-33)
Selects an interrupt rate of 1024ints/sec.
Selects an interrupt rate of 2048ints/sec.
Selects an interrupt rate of 4096ints/sec.
The previous three options are used when a smaller delay is wanted then
the 8192ints/sec option allows.
EX. For slower AT's (like the original 6mhz IBM AT).
To slow down a 80486 to 80386 speeds.
Slow down a game a little making it easer to play.
Restores the int's/second back to the normal 8192. This is the
default when the program is first installed.
Disables AT-SLOW's delay and hot-keys.
AT-SLOW is completely inactive at this point and can only be reactivated
by the enable command or entering a new delay or CPU value.
Enables AT-SLOW's delay and Hot-keys with the previous delay value.
Disables AT-SLOW's delay but not the hot-keys. When in standby mode
AT-SLOW checks for the hot-key sequence to reactivate and for exit to
DOS. It also insures that the hot-keys are not disabled by any other
program while in standby mode.
Using standby mode you can set the delay you want for a game, then
activate the delay after the program is loaded.
Disable AT-SLOW and remove it from memory
Show AT-SLOW's current status. Use this function to determine the
delay value after you have fine tuned it using the hot-keys or the CPU
Using AT-SLOW's Hot-keys
AT-SLOW's hot-keys are activated in a way that prevents them from
interfering with other programs function keys.
To use AT-SLOW's hot-keys they must be activated first. This is done
by pushing the ALT key twice in a row. Pushing the ALT key again or any
other key except for AT-SLOW's hot-keys will deactivate them. This is done
so that the hot-keys cannot be activated by accident. For best results in
activating the hot-keys push another key other then the hot-keys (such as
CTRL or SHIFT) to clear any sequence already started, then push the ALT
key twice in a row.
Once the hot-keys have been activated you can use them to speedup and
slowdown the computer or remove AT-SLOW and all programs loaded after it
including the one that is curently running from memory and exit to DOS.
The Hot-keys are:
E Enables the delay value.
D Disables the delay value.
Gray + Increases delay by 1 each time pushed.
Gray - Decreases delay by 1 each time pushed.
ESC Pushed 4 times in a row will cause the computer to exit to DOS
The (E) key enables the delay with the previous value. So by entering
a command such as:
the program requiring slowdown can be loaded at full computer speed and
then the desired delay can be enabled by using the (E) hot-key.
After hot-keys have been enabled pushing any key other than the 5
mentioned above will deactivate the hot-keys and the ALT will have to
be pushed twice in a row again to re-activate them.
More information about the Hot-key to DOS
This option can be very useful and dangerous too. It should be used
with care and only when necessary.
This option works by making a snapshot of memory when AT-SLOW is
loaded. Then when the sequence is activated all programs loaded after
AT-SLOW are removed from memory (much like other TSR memory managers) and
the computer system is restored to the state it was in before AT-SLOW
was loaded. Then AT-SLOW is also removed from memory and the system
returns to the DOS prompt.
Care should be used when activating the exit to DOS function. Wait
until the program is not active (such as waiting for input). Do not
activate when program is reading or writing to disk. This could cause
loss of data.
In must cases the system should have been restored to a reliable
condition however, don't exit to DOS from a game and then start work on
that spreadsheet you've been working on for the past two weeks, reboot
instead. This option allows you to run several games and other non-
critical programs that normally require you to reboot to exit, without
In most cases AT-SLOW's exit to DOS function should be as reliable
as other TSR memory managers. Experiment, over time you will find out
what works and what doesn't. In time this function may become even more
valuable then the slowdown function.
If you find AT-SLOW useful:
This program is copyrighted and may only be distributed
in unmodified form and with the .DOC & .DIZ file included.
A lot of time and effort went into the finding of information
and writing of AT-SLOW. So if you find this program useful (and I'm
sure you will) and would like to support the development of more PC-AT
(and other high performance computers) related software.
Please fill out the registration form on the following page and send it
along with the registration fee to:
David Keil / Better Software Co.
10 W. Wilburn Ave.
Greenville, S.C. 29611
This program is provided AS IS without any warranty, expressed
or implied, including but not limited to fitness for a particular
Please support quality shareware by registering it.
We thank you for your support.
AT-SLOW PAID Registration form
Remit To: David Keil / Better Software Co.
10 W. Wilburn Ave.
Greenville, SC 29611
Voice (803) 295-4971
Data #1 (803) 269-7899
Data #2 (803) 269-7045
____ AT-SLOW Registration $15.00
____ Update on 5.25 inch disk $ 0.00
____ Update on 3.25 inch disk $ 0.00
____ Update to be downloaded off BBS $ 0.00
____ Outside USA shipping & handling $ 5.00
Total amount enclosed $_______
Payment by check or money order (U.S. bank or branch)
Make check payable to: Better Software Co.
..... Following needed for download of upgrade off BBS
Work Phone _____ __________ Home Phone _____ __________
The following will be your user ID:
First Name _____________
Last Name _____________
An account will be setup for you within 24 after receiving your
registration (10 days for personal check). Mail will be left for you which
will tell you how to download your upgrade. Registered users will be notified
on the BBS of upgrades in AT-SLOW.
..... Following needed for shipment of upgrade.