Epson 4000 - Manual (Page 46)

Changing the Processor Speed
Your computer’s processor can operate at two speeds: fast
speed (the speed of your microprocessor) or slow speed
(8 MHz). The slow speed is available to provide compatibility
with older application programs.
When your computer is operating at fast speed, the TURBO light
on the front panel is on. When the computer is operating at
slow speed, the light is off.
You should use fast 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.
Some copy-protected programs require the computer to run at
slow speed while accessing the program on a diskette. These
programs also usually require you to leave a key disk-the
diskette that contains the copy protection-in the diskette
drive. If you use a copy-protected program, you can change the
speed to slow to access the diskette and return it to fast speed
when you are finished.
You can change the processor speed temporarily by entering
one of the following commands from the numeric keypad on
your keyboard:
To select slow speed, hold down the Ctrl key and the Alt key
simultaneously and then press the - key on the numeric
keypad. This turns off the speed light.
To select fast speed, hold down the Ctrl and Alt keys and
press + on the numeric keypad. The speed light comes on.
3-6 Using Your Computer