Time running fast

[Guest]

I have a PBDOS program that displays the time on the screen.
The program is running on a WIN2K SP3 machine. After the program
runs for a while (20-30 minuites) the time is several minutes
ahead of the time displayed on the task bar.

Any ideas why?

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[Davide Vecchi]

Talking about TIME$ or TIMER or other ?

Is it the time showed by your program that runs faster, or the time in the taskbar that becomes slower ? Might it be that your program running in the DOS box takes too much CPU giving problems to Windows ?

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Davide Vecchi
[email protected]

[This message has been edited by Davide Vecchi (edited November 27, 2002).]

[Guest]

Here is the code I using to displat the time

Locate 1,72
Print GoodTime(Time$)+" "+Toggle$

FUNCTION GoodTime(EdStr As String) As String
DIM A AS LOCAL STRING
DIM HOUR AS LOCAL INTEGER
DIM PA AS LOCAL STRING
If Len(EdStr)=8 Then A=Left$(EdStr,2)+Mid$(EdStr,4,2) Else _
A=EdStr
REPLACE " " WITH "0" IN A
Hour=Val(Left$(A,2))
If Hour>12 then 'Takes time in HH:MM:SS or HHMM format and
DECR Hour,12 'returns in HH:MM{am|pm} non-military
PA="pm"
ElseIf Hour=12 then
PA="pm"
ElseIf Hour=0 then
Hour=12
PA="am"
Else
PA="am"
End If
GoodTime=Using$("##",Hour)+":"+Right$(A,2)+PA
End FUNCTION

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[Tom Hanlin]

The "DOS" you see under NT-based operating systems (like Win2k) is
actually a virtual DOS box. Each "box" gets its own pretend copy of
the whole computer, with certain safeguards in place to avoid having
the "box" conflict with other programs. As part of this virtual DOS,
your "DOS" programs get their own copy of the system time and date,
which runs separately from the real system time and date.

Try setting TIME$ to something different in your DOS program, and
note that the Windows time doesn't follow suit.

PB/DOS needs to do some twiddling with the timer chip in order to
provide better timing resolution. It has secondary routines in place
that keep the time/date value at its normal speed, regardless. But,
these routines were designed for a real timer chip, not the virtual
timer chip provided by the DOS box. My guess would be that Win2k is
not emulating the timer chip with perfect fidelity, causing some
drift in the apparent time/date value. That's just a guess, though.


------------------
Tom Hanlin
PowerBASIC Staff

[Clay Clear]

Tom,

Would this Windows-"virtualized" system time also apply to directly
reading the system clock with INT &H21 service &H2C? I have a
PBU function that does that, and if you think it'll help, I can post
the code for Doug? Doug - please note that my PBU code has ONLY
been tested under my Win98SE, so USE AT YOUR OWN RISK! Also, I have
not run it cyclically for long periods of time, so I do not know if
it would have the same problems as the PB/DOS TIME$ command. Might
be an idea to wait for Tom to answer.


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[Clay Clear]

Doug,

Here's a "beefed up" version of my PBU code. My original code only
returned the same info that the native PB/DOS TIME$ does. This code
will retrieve the time from the system clock, convert it to 12-hour
clock, and append the appropriate "AM" or "PM".

USE AT YOUR OWN RISK! It has NOT been tested on a Platform 2 OS!
I also do not know if it will return better results than the TIME$
verb!

$COMPILE UNIT
'
DEFSTR S
DEFINT I
'
%FLAGS = 0
%AX    = 1
%BX    = 2
%CX    = 3
%DX    = 4
%SI    = 5
%DI    = 6
%BP    = 7
%DS    = 8
%ES    = 9
'
FUNCTION GetTime2$() PUBLIC
    I1 = 0
    I2 = 0
    ! PUSH DS
    REG %AX, &H2C00
    CALL INTERRUPT &H21
    I1 = REG(%CX)
    I2 = REG(%DX)
    ! POP DS
    IHour = (I1 AND &HFF00)
    SHIFT RIGHT IHour, 8
    IMinutes = (I1 AND &H00FF)
    ISeconds = (I2 AND &HFF00)
    SHIFT RIGHT ISeconds, 8
    SELECT CASE IHour
        CASE 0
            SHour = "12"
            SAMPM = " AM"
        CASE 12
            SHour = "12"
            SAMPM = " PM"
        CASE 1 TO 11
            SHour = TRIM$(STR$(IHour))
            SAMPM = " AM"
        CASE > 12
            SHour = TRIM$(STR$(IHour - 12))
            SAMPM = " PM"
    END SELECT
    SMinutes = USING$("##", IMinutes)
    SSeconds = USING$("##", ISeconds)
    REPLACE " " WITH "0" IN SMinutes
    REPLACE " " WITH "0" IN SSeconds
    FUNCTION = SHour + ":" + SMinutes + ":" + SSeconds + SAMPM
END FUNCTION

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[This message has been edited by Clay Clear (edited November 27, 2002).]

[Guest]

The same app runs on several machines that are part of win2k
peer to peer network, the other machines use the following

NET TIME \\"+TimeServerName+" /SET /YES"

to keep their clocks at the same time. The app skips the above
code if it is running on the "timeserver". The other machines
time stays the same as the time on the task bar.

I will have the timeserver shell to net time every few minutes
and see if that resolve the problem.

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[Tom Hanlin]

Clay, DOS only "directly" reads the system clock on start-up. After
that, it maintains its own cheap imitation copy. It's a legacy thing
from the days when a "real-time clock" was an optional add-on card,
without which you were expected to enter the time and date whenever
you started up DOS. Ah, the good old days!

It's this software copy of the real clock that's getting messed over.
Doug's NET TIME approach should work fine, although it's probably
overkill-- Windows still knows what the real time is, so the program
just needs to ask Windows every now and then.

------------------
Tom Hanlin
PowerBASIC Staff