Epson 486SX - Manual (Page 48)

You can also set the processor to change its speed
automatically. This enables the computer to switch to low
speed whenever it needs to access a diskette drive, but run at
high speed for all other operations.
Note
You may not want to use the automatic setting for certain
copy-protected programs. See “Changing the Processor
Speed” in Chapter 4 for more information.
In addition to selecting the default operating speed through
the Setup program, you can change the speed temporarily by
entering a keyboard command or running the ESPEED
program. See “Changing the Processor Speed” in Chapter 4
for details.
Follow these steps to set your processor speed:
1. At the main Setup menu, highlight Processor speed.
The current status appears:
Speed: High
If the displayed setting is correct, skip the rest of this
section.
2. To change the processor speed, press The cursor
moves into the submenu and you see another menu:
High
Automatic
Low
2-14 Running the Setup Program