Could you post the output from the following on one machine that gives good results and one that gives bad:

#! perl -slw
use strict;
use Time::HiRes qw[ gettimeofday time ];

use Win32::API::Prototype;

ApiLink( 'kernel32', q[
    BOOL QueryPerformanceCounter( LARGE_INTEGER *lpPerformanceCount )
]) or die $^E;

ApiLink( 'kernel32', q[
    BOOL QueryPerformanceFrequency( LARGE_INTEGER *lpPerformanceCount 
+)
]) or die $^E;

sub int64_to_NV {
    my( $lo, $hi ) = unpack 'VV', $_[ 0 ];
    return $hi * 2**32 + $lo;
}

my $frequency = ' ' x 10;
QueryPerformanceFrequency( $frequency ) or die $^E;

print 'Counter changes ', int64_to_NV( $frequency ), ' times/second';

for ( 1 .. 10 ) {
    QueryPerformanceCounter( $frequency )or die $^E;
    print 'QPC: ',int64_to_NV( $frequency );
}


printf "GToD: %.8f\n", scalar gettimeofday() for 1 .. 10;
printf "Time: %.8f\n", time() for 1 .. 10;
[download]

If I run your script on my machine (bad) I get:

Counter changes 3579545 times/second
QPC: 35752003971
QPC: 35752004170
QPC: 35752004356
QPC: 35752004527
QPC: 35752004695
QPC: 35752004854
QPC: 35752005017
QPC: 35752005169
QPC: 35752005333
QPC: 35752005487
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
GToD: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
Time: 1219149309.90625000
[download]

And here is the output from a "good" machine:

Counter changes 3579545 times/second
QPC: 76031246430
QPC: 76031246657
QPC: 76031246790
QPC: 76031247127
QPC: 76031247273
QPC: 76031247479
QPC: 76031247686
QPC: 76031247838
QPC: 76031247972
QPC: 76031248165
GToD: 1219150762.25000000
GToD: 1219150762.25004410
GToD: 1219150762.25007610
GToD: 1219150762.25010900
GToD: 1219150762.25013900
GToD: 1219150762.25017500
GToD: 1219150762.25020500
GToD: 1219150762.25024100
GToD: 1219150762.25027490
GToD: 1219150762.25030590
Time: 1219150762.25033810
Time: 1219150762.25036690
Time: 1219150762.25039600
Time: 1219150762.25042800
Time: 1219150762.25047900
Time: 1219150762.25053190
Time: 1219150762.25058200
Time: 1219150762.25063110
Time: 1219150762.25066710
Time: 1219150762.25069900
[download]

It's not your hardware!

Your machine is equally capable of high resolution as the "good" machine. That's identified by the first line: Counter changes 3579545 times/second which displays the granularity of the timer, which is the same on both machines.

That means if they are both using the same version of Time::HiRes, then they should be giving the same results. The first thing I would try is re-installing the module. From CPAN if you are compiler-capable. From a PPM otherwise. And, if your paranoid like me, you'll blow away the existing files first:

<yourperl>/lib/Time::HiRes.pm
<yourperl>/lib/auto/Time/HiRes/*
[download]

If the problem persists after that, something very hookey is going on with your install.

---

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"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

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