adnan@screech.rice.edu (Sarmad Adnan) (11/03/90)
I need to write a piece of code that would allow me to
change the speed of the cpu (in a dual speed AT, with
AMI bios) through software.
Some of the compaq have a 'MODE speed' command implimented
in the dos does something similar exist or can be written
for a computer with AMI bios ?.
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Sarmad Adnan (adnan@rice.edu)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~briggs@tamunix (Mark Lowe) (11/03/90)
In article <1990Nov3.014940.9232@rice.edu> adnan@screech.rice.edu (Sarmad Adnan) writes: > >I need to write a piece of code that would allow me to >change the speed of the cpu (in a dual speed AT, with >AMI bios) through software. >Some of the compaq have a 'MODE speed' command implimented >in the dos does something similar exist or can be written >for a computer with AMI bios ?. > Sarmad Adnan (adnan@rice.edu) I once wrote a short machine language routine for a former roommate's computer that had two speeds. He has one of those computers that allows you to toggle between speeds by hitting CTRL-ALT-HYPHEN or some such keystroke. I messed around with the system enough to figure out that an unused bit in I/O port 60 or 61 controlled the speed. Make sure you disable interrupts before toggling the bit, though, or you'll hang the machine. I hope this vague description gives you some clues. Mark C. Lowe - KB5III
rcollins@altos86.Altos.COM (Robert Collins) (11/09/90)
In article <9802@helios.TAMU.EDU> briggs@tamunix (Mark Lowe) writes: >I messed around with the system enough to figure out that an unused bit in >I/O port 60 or 61 controlled the speed. Make sure you disable interrupts >before toggling the bit, though, or you'll hang the machine. > >I hope this vague description gives you some clues. > By no means is CPU speed change consistent among machines. Some use an I/O port. Some use the keyboard controller, some use memory mapped I/O. And you can almost guarantee, that writing to I/O port 61 in this guy's machine won't do it (unless it is the same motherboard as the abovementioned). The bottom line? CPU Speed change is hardware/motherboard dependant. -- "Worship the Lord your God, and serve him only." Mat. 4:10 Robert Collins UUCP: ...!sun!altos86!rcollins HOME: (408) 225-8002 WORK: (408) 432-6200 x4356