[AccessD] Classes and Events - EVENTS NOT REQUIRED

Stuart,

My understanding of the 10 ms deal is simply that each time slice allocated by the OS (pre-emptive 
multitasker) is 10 ms.  The tick count is still 1 ms regardless of the time slice length, even for 
XP / 2K.  Again my understanding is that the tick count comes off the system clock.  I will admit it 
has been a long time since I looked at that stuff however.

http://www.experts-exchange.com/Programming/Misc/Q_21889245.html

Who know how accurate these "experts" are, but it SOUNDS good!  ;-)

John W. Colby
www.ColbyConsulting.com


Stuart McLachlan wrote:
> JC is using the timeGetTime() API call.   
> 
> Windows95/98 has a 1ms resolution for this
> W2K/XP generally have a resolution of about 10ms 
> My Vista machiine has a  resolution of 1ms, so it looks as though MS may have fixed this.
> 
> Note however:
> - you can use the timeBeginPeriod() API call to increase the granularity in W2K/XP.
> - it is a low priority call and can be delayed or even dropped if the queue is busy.
> 
> Another problem is that it rolls over every 49 days so there is a *very* slight possibility that 
> the Stop time may be much smaller than the Start time.  
> 
> If your programmers want accurate time, they should be using 
> QueryPerformanceFrequency and QueryPerformanceCounter, using them you can get sub- 
> microsecond (close to nanosecond) accuracy.
> 
> Try pasting this into a Module and see what your numbers are like.
> 
> 
> <start code>
>        Option Explicit
> 
>       Declare Function QueryPerformanceCounter Lib "Kernel32" _
>                                  (X As Currency) As Boolean
>       Declare Function QueryPerformanceFrequency Lib "Kernel32" _
>                                  (X As Currency) As Boolean
>       Declare Function GetTickCount Lib "Kernel32" () As Long
>       Declare Function timeGetTime Lib "winmm.dll" () As Long
> 
>       Sub Test_Timers()
>       Dim Ctr1 As Currency, Ctr2 As Currency, Freq As Currency
>       Dim Count1 As Long, Count2 As Long, Loops As Long
>       '
>       ' Time QueryPerformanceCounter
>       '
>         If QueryPerformanceCounter(Ctr1) Then
>           QueryPerformanceCounter Ctr2
>           Debug.Print "Start Value: "; Format$(Ctr1, "0.0000")
>           Debug.Print "End Value: "; Format$(Ctr2, "0.0000")
>           QueryPerformanceFrequency Freq
>           Debug.Print "QueryPerformanceCounter minimum resolution: 1/" & _
>                       Freq * 10000; " sec"
>           Debug.Print "API Overhead: "; (Ctr2 - Ctr1) / Freq; "seconds"
>         Else
>           Debug.Print "High-resolution counter not supported."
>         End If
>       '
>       ' Time GetTickCount
>       '
>         Debug.Print
>         Loops = 0
>         Count1 = GetTickCount()
>         Do
>           Count2 = GetTickCount()
>           Loops = Loops + 1
>         Loop Until Count1 <> Count2
>         Debug.Print "GetTickCount minimum resolution: "; _
>                     (Count2 - Count1); "ms"
>         Debug.Print "Took"; Loops; "loops"
>       '
>       ' Time timeGetTime
>       '
>         Debug.Print
>         Loops = 0
>         Count1 = timeGetTime()
>         Do
>           Count2 = timeGetTime()
>           Loops = Loops + 1
>         Loop Until Count1 <> Count2
>         Debug.Print "timeGetTime minimum resolution: "; _
>                     (Count2 - Count1); "ms"
>         Debug.Print "Took"; Loops; "loops"
>       End Sub
> 						
> <end code>