Clock speed?

[Ralph]

I was just thinking that, if a program can detect the computer speed for the computer it is running on, we could just use that value as part of our short program pauses, so that the pause time would be the same length of real time, no matter the particular speed of the computer in use. For instance, if my computer clock speed = 3GHx, I could write use it for a program, like this:

Code:

CLS
SCREEN 13
'LIGHTNING
CS = 3                          'clock speed, in MHz
T = 30000*CS                   'a short time
bg = 0                          'clock speed, in MHz

FOR I= 1 TO 20
   LINE (0,0)-(319.199),15,BF   'show the screen as bright white
   FOR J = 1 TO T:NEXT J        'short pause
   LINE(0,0)-(319,199),bg,BF    'show the screen with the bg color
   FOR J = 1 TO T:NEXT J        'short pause
NEXT I

So, is it possible - and fairly easy - to detect the computer's clock speed? If so, how?

[DrV]

Clock speed is not really a good thing to base delays on, for various reasons, the most important being that you can't depend on your program getting the CPU all of the time (unless you're running on DOS). If you need to wait for a particular amount of real time, just check TIMER in a loop.

[Ralph]

DrV:

The best I can get with TIMER is something like 0.56 or so of a second. I can't get less! I'll give it a try, though.

(Pause, to give it a try)

I'm back. Nope, it didn't work good enough for my lightning program, using this code:

Code:

T1 = 0.00000005
T0 = TIMER
WHILE TIMER-0 < T1:WEND

I started with T1 = 0.5, and worked my self all the way down to
T1 = 0.00000005. Am I doing it right?

[nkk_kan]

But does that count clock speed?


Don't u need to use an ASM Interuppt to find it out?

[DrV]

You might be interested in these articles: http://faq.qbasicnews.com/?blast=TimerTopics

[Ralph]

I tried the CLOCK function from the link in DrV's post, with the code below. My part is the "to test it:" part, where I'm trying to flash the screen to show lightning. It does a very poor job, as the timing I get seems very inconsistent!

Code:

DECLARE FUNCTION CLOCK& ()

'to test it:
SCREEN 13
CLS
t1 = .02
t2 = 2 * t1

FOR I = 1 TO 1220
  clockVal! = CLOCK / 4660.859#
  LINE (0, 0)-(319, 199), 15, BF
  WHILE (TIMER - clockVal!) < t1: WEND
  LINE (0, 0)-(319, 199), 0, BF
  WHILE (TIMER - clockVal!) < t2: WEND
NEXT I



FUNCTION CLOCK&

  ' Get the number of timer ticks at
  ' 0000:046C
  DEF SEG = 0
  Ticks& = PEEK(&H46C)
  Ticks& = Ticks& + PEEK(&H46D) * 256&
  Ticks& = Ticks& + PEEK(&H46E) * 65536
  DEF SEG

  ' Latch the counter and obtain the PIT
  ' countdown status.
  OUT &H43, &H4
  LSB = INP(&H40)
  HSB = 255 - INP(&H40)

  ' Compute the CLOCK& value
  CLOCK& = Ticks& * 256& + HSB

END FUNCTION

[Dinosaur]

Ralph

The only way to use timer tick accurately is to get the interupt to update your variable each time the interupt happens. I use a scheme as below to accurately time events, without creating a lot of overhead.

Code:

'---------------------------------
TYPE TIMES
    Clk        AS    INTEGER
    Divider        AS    INTEGER
    Speed        AS    INTEGER
    Increment    AS    LONG
    Msec        AS    LONG
    NowTime        AS    LONG
    KeyTime                   AS    LONG
    PassCount    AS           LONG
    StartTime                    AS           LONG
    WaitState                    AS    LONG
    RunTime                  AS            LONG
    OldTime                  AS            LONG
    ShowTime              AS            LONG
    Hours                     AS           INTEGER
    Minutes                 AS            INTEGER
    Seconds                 AS            INTEGER
    Tyd        AS    STRING * 7
END TYPE                            
COMMON SHARED TIMES AS TIMES
'---------------------------------
DECLARE FUNCTION TsrTime& (byval a&,byval B&)

'First Hook the Interupt so that everytime the clock tick increments,
'your variable increments.(If you want the asm routine that I can send it)

A& = TsrTime& (byval varptr(Times.NowTime),byval varseg(Times.NowTime))

'I write my programs so that I never hang around or wait for a delay.
'Then at the beginning there is a main loop

DO
    TimeShow
    'call whatever else here,

LOOP

'So if you need an accurate delay.
Times.StartTime = Times.Msec
'then in your loop
IF Times.Msec - Times.StartTime > 12 THEN ......


'You can also use it to see how long your loop takes
'by printing Times.Increment on the screen

SUB TimeShow
        Times.PassCount  = Times.PassCount  + 1        'increment the program loops        
        Times.Msec = clng((Times.NowTime * 54.9254) + (Times.Increment \ 1000 ))    '
        '-----------------------------------------------
        IF Times.NowTime > Times.OldTime  THEN                'if a tick has happened ,recalculate
            Times.Increment  = (54.9254 / Times.PassCount) * 1000     '55 msec / Nr of Passes = msec per pass
            Times.OldTime    = Times.NowTime
            Times.PassCount  = 0
        END IF
END SUB

[Ralph]

Thanks to all that suggested different methods of obtaining the desired time delay for values much less than 1 second. As I am getting over my head, I will stay with my present method, which seems "good enough", even though far from perfect. You know, the old KISS principle, which I had forgotten to apply!