var
  Form1: TForm1;
  nOldIdleTime: Int64 = 0;
  nOldSystemTime : INT64 = 0;
  nNewCPUTime : ULONG = 0;

const
  SYS_BASIC_INFO = 0;
  SYS_PERFORMANCE_INFO = 2;
  SYS_TIME_INFO = 3;

type
  SYSTEM_BASIC_INFORMATION = packed record
    dwUnknown1 : DWORD;
    uKeMaximumIncrement : ULONG;
    uPageSize : ULONG;
    uMmNumberOfPhysicalPages: ULONG;
    uMmLowestPhysicalPage : ULONG;
    uMmHighestPhysicalPage : ULONG;
    uAllocationGranularity : ULONG;
    pLowestUserAddress : POINTER;
    pMmHighestUserAddress : POINTER;
    uKeActiveProcessors : POINTER;
    bKeNumberProcessors : BYTE;
    bUnknown2 : BYTE;
    wUnknown3 : WORD;
  end;

  SYSTEM_PERFORMANCE_INFORMATION = packed record
    nIdleTime : INT64;
    dwSpare : array[0..75]of DWORD;
  end;

  SYSTEM_TIME_INFORMATION = packed record
    nKeBootTime : INT64;
    nKeSystemTime : INT64;
    nExpTimeZoneBias : INT64;
    uCurrentTimeZoneId : ULONG;
    dwReserved : DWORD;
  end;

  function NTQuerySystemInformation(SystemInformationClass: Longint;
                                    SystemInformation: Pointer;
                                    SystemInformationLength: Longint;
                                    ReturnLength: Longint): Longint; stdcall;
                                    external 'ntdll.dll' name 'NtQuerySystemInformation';

implementation

{$R *.dfm}


function GetCPUUsage: Integer;
var
  spi : SYSTEM_PERFORMANCE_INFORMATION;
  sti : SYSTEM_TIME_INFORMATION;
  sbi : SYSTEM_BASIC_INFORMATION;
begin
  if (NTQuerySystemInformation(SYS_BASIC_INFO, @sbi, sizeof(SYSTEM_BASIC_INFORMATION), 0) = NO_ERROR) then
  begin
    if (NTQuerySystemInformation(SYS_TIME_INFO, @sti, sizeof(SYSTEM_TIME_INFORMATION), 0) = NO_ERROR) then
    if (NTQuerySystemInformation(SYS_PERFORMANCE_INFO, @spi, sizeof(SYSTEM_PERFORMANCE_INFORMATION), 0)= NO_ERROR) then
    begin
      if (nOldIdleTime <> 0) then
      begin
        nNewCPUTime:= trunc(100-((spi.nIdleTime-nOldIdleTime)/(sti.nKeSystemTime-nOldSystemTime)*100)/sbi.bKeNumberProcessors+0.5);
        if (nNewCPUTime <> nOldIdleTime) then
        begin
          Result := nNewCPUTIME;
        end;
      end;
      nOldIdleTime := spi.nIdleTime;
      nOldSystemTime := sti.nKeSystemTime;
    end;
  end;
end;