Epson 3865X Plus - Manual (Page 96)

There are three ways to change the processor speed:
Run the Setup program on your Reference diskette
Enter a keyboard command
Run the ESPEED program.
If you frequently use programs that require the processor to
operate at low speed or require the automatic speed change
when your computer is accessing a diskette, use the Setup
program to change the processor speed. See Chapter 2 for
instructions.
If you use these programs only occasionally, you should use the
keyboard commands or the ESPEED program (described below)
to change the processor speed.
Entering Keyboard Commands
Whenever you are at an MS-DOS command prompt, you can
change the processor speed by entering one of the following
commands:
CTRL ALT + Changes the processor speed to high
(16 MHz).
CTRL ALT -
Changes the processor speed to low
(simulated 8 MHz).
CTRL ALT *
Sets the processor speed to change to low
speed automatically when the computer is
accessing a diskette.
4-4 Enhancing System Operating