Epson 486SX - Manual (Page 78)

One batch file that you may find particularly useful is called
AUTOEXEC.BAT. Every time you turn on your computer,
MS-DOS looks for the AUTOEXEC.BAT file and automatically
executes each of the commands in the file.
When you install MS-DOS, it creates an AUTOEXEC.BAT file
for you. To modify the file or replace it with a new one, you can
use the COPY or EDLIN command, a text editor, or a word
processing program that can save a file as text-only. Be sure to
name the file AUTOEXEC.BAT and store it in the root directory
of the hard disk or diskette from which you load MS-DOS.
See your MS-DOS manual for more information about creating
and using batch files.
Changing the Processor Speed
Your computer’s processor can operate at two speeds: high and
low. High speed is 25 MHz or 50 MHz (depending on your
model) and low speed simulates an 8 MHz processor speed. At
high speed, the computer can access memory faster than at low
speed. The default setting is high speed unless you changed it
in Setup to low or to change automatically.
Note
When your computer is operating at high speed, the TURBO
light on the front panel is on. It is off when the computer is
operating at low speed.
You should use high speed for almost everything you do
because your programs will work faster. However, certain
application programs have specific timing requirements and
can run only at the slower speed. See your software manual to
determine if this is the case.
4-2 Enhancing System Operations