Want to control CPU internal clock

[Barry Kaufman]

I want to set clock multiplier in Athlon XP-M 2400+ in DOS. Have
eMachines M5312 laptop with an MS-DOS 7.1 bootable partition. Bios
defaults the CPU clock to full speed (1.8GHz) and the thing then gets
tooo hot. When booted in WIN XP partition, CPU is throttled by ACPI and
runs cool.

So with PowerBasic 3.5 for DOS, I want to issue commands to set CPU to
lower clock speed, perhaps around half the maximum. Would also be
nice to program core voltage lower commensurate with the lower clock
speed. I would appreciate info on memory or I/O locations of control
registers, bit pattern, sequence of instructions, etc. to change
these CPU parameters.

Thanks, Barry.

[Wayne Suite]

Locations / Control

Sounds like CMOS locations 2 me.

[Paul Dixon]

Bary,

Bios defaults the CPU clock to full speed (1.8GHz) and the thing then gets tooo hot

That suggests that you need to look into the CPU cooling. The CPU with the proper heatsink and fans should be able to run indefinitely at full speed.
Check that the CPU fan is working and not covered in dust, the heatsink is properly mounted, there are no obstructions to air flow in the case and that the contact between heatsink and CPU is using heat sink compound.

Paul.

[Wayne Suite]

Cmos

This might help point u in the direction some.

This unit (by an unknown other) shows you how it's done. The CMOS memory is
not part of the PC's main memory. Values are written/read by accessing an
I/O port.
 
}
unit CMOS;
 
Interface
 
const
     ClockSec  = $00;    { RTclock seconds }
     ClockMin  = $02;    { RTclock minutes }
     ClockHour = $04;    { RTclock hours }
     ClockDOW  = $06;    { RTclock day of week }
     ClockDay  = $07;    { RTclock day in month }
     ClockMon  = $08;    { RTclock month }
     ClockYear = $09;    { RTclock year (mod 100)}
     AlarmSec  = $01;    { Alarm seconds }
     AlarmMin  = $03;    { Alarm minutes }
     AlarmHour = $05;    { Alarm hours }
     Diskettes = $10;    { Floppy disk type byte }
     HardDisk  = $12;    { Regular hard disk type }
     HDExt1    = $19;    { Extended hard disk type, unit 1 }
     HDExt2    = $1A;    { Extended hard disk type, unit 2 }
     Equipment = $14;    { Equipment list }
     CheckLo   = $2F;    { Checksum low }
     CheckHi   = $2E;    { Checksum high }
     BaseLo    = $15;    { Base mem low }
     BaseHi    = $16;    { Base mem high }
     ExpdLo    = $17;    { Expansion mem size low }
     ExpdHi    = $18;    { Expansion mem size high }
     StatRegA  = $0A;    { Status Register A }
     StatRegB  = $0B;    { Status register B }
     StatRegC  = $0C;    { Status register C }
     StatRegD  = $0D;    { Status register D }
     DiagStat  = $0E;    { Diagnostic status byte }
     ShutDown  = $0F;    { Shutdown status byte }
     Century   = $32;    { BCD Century number }
     AltExpdLo = $30;    { Expansion mem size low (alternate) }
     AltExpdHi = $31;    { Expansion mem size high (alternate) }
     InfoFlags = $33;    { Bit 7 set = top 128k installed, bit
                           6 set = first user message (?) }
 
function ReadCmos(Address: byte): byte;
          { Returns the byte at the given CMOS ADDRESS }
 
procedure WriteCmos(Address, Data: byte);
          { Writes DATA to ADDRESS in CMOS ram }
 
procedure SetCMOSCheckSum;
          { Sets the CMOS checksum after you've messed with it :-}
 
{ The following bytes are RESERVED: $11, $13, $1B-$2D, and
  $34-$3F ($3F marks the end of the CMOS area).  You'll note that
  some of these are included in the checksum calculation. }
 
implementation
 
const
     CmosAddr  = $70;    { CMOS control port }
     CmosData  = $71;    { CMOS data port }
 
function ReadCmos(Address: byte): byte;
begin
     port[CmosAddr] := Address;
     ReadCmos := port[CmosData]
end; {ReadCmos}
 
procedure WriteCmos(Address, Data: byte);
begin
     port[CmosAddr] := Address;
     port[CmosData] := Data
yend; {WriteCmos}
 
procedure SetCMOSCheckSum;
{ The checksum is simply the sum of $10 to $2D 
  (some of these bytes are reserved) }
 
var
     I, Sum: word;
begin
     Sum := 0;
     for I:= $10 to $2D do Sum := Sum + ReadCmos(I);
     WriteCmos(CheckHi, Hi(sum));
     WriteCmos(CheckLo, Lo(sum));
end; {SetCMOSCheckSum}
 
end.