Specifications
3 - 5
3.3 CPU AND BUS SPEED INITIALIZATION
One of the most important system parameters to configure is the half-speed option for the CPU
and/or expansion bus. In most installations, you will want to have the CPU operate at full speed.
Assuming 12 or 16 MHz operation of the board's CPU, it is most common to operate the bus at
"half-speed", due to the fact that many PC and AT bus expansion boards require a maximum bus
speed of 8 MHz.
There are two ways to control the half-speed options:
3.3.1 Fixed Speed Operation (Using SETUP)
The onboard nonvolatile configuration memory contains two parameters which indicate to the
ROM-BIOS whether to automatically set the CPU and/or expansion bus half-speed options, on
powerup or reset. The Ampro SETUP function allows you to store the desired values for these two
parameters in the board's Configuration Memory. Note that the effect of using SETUP to change
either half-speed option does not take effect until you reboot the system.
3.3.2 Variable Speed Operation (Using SETSPEED)
During system operation, you can dynamically alter the half-speed option for either the CPU or
expansion bus using the Ampro SETSPEED utility. The SETSPEED program can be invoked
manually, from the DOS command line. Alternatively, a SETSPEED command can be issued
automatically, from within a batch file. The effect of using SETSPEED is immediate, and does not
require rebooting the system.
Some examples of when you might use the SETSPEED command are:
n To reduce CPU speed for the purpose of conserving power during battery operation (up to
15%).
n To allow the use of a program which was intended for operation on a slower computer; you
might run the speed-critical from a batch file such as this:
SETSPEED /P=LO
SLOWPROG
SETSPEED /P=HI
n To allow the use of an expansion bus card that cannot operate at full bus speed; you might
shift the bus to half-speed prior to running the slow card's operating software, and then return
the bus to full speed afterwards, as in the previous example.
n For a brief SETSPEED help screen, use the command:
A>SETSPEED ?<Enter>