Epson 486SX - Manual (Page 82)

(This command sets the processor speed to change to low speed
automatically when the computer accesses a diskette.)
If you include the switch when you type the initial ESPEED
command, the program changes the speed without displaying
the command options.
The processor speed you set remains in effect until you change
it using the Setup program, a keyboard command, or the
ESPEED program again or until you press the
RESET
button or
turn off the computer.
Entering the ESPEED command in a batch file
You may want to run the ESPEED program by including the
command in a batch file. For example, let’s say you have a
program called SLOWDOWN which requires a slower
processor speed. You could include the following commands in
a batch file to start the SLOWDOWN program:
ESPEED /A
SLOWDOWN
You could name the batch file SLOW.BAT. Whenever you need
to run the SLOWDOWN program, insert the program diskette
into drive A. Then type
SLOW
and press The computer
changes the processor speed to automatic and starts the
program.
4-6 Enhancing System Operations