I've certainly seen suspect behaviour from microtime() too, but I
never chased it down.

    -- Lennart

David Laight wrote:

>I've added some diagnostics to the end of (my) microtime()
>code to detect time travel.
>
>microtime leapt back to 3d46cc10:44307 (+2457) from 3d46cc10:44326 (+2476)
>microtime leapt back to 3d46cc9c:41be2 (+2442) from 3d46cc9c:41c06 (+2466)
>microtime leapt back to 3d46cc9e:6ddcd (+270d) from 3d46cc9e:6ddfd (+2d)
>microtime leapt back to 3d46ccb0:77669 (+2369) from 3d46ccb0:7768b (+238b)
>microtime leapt back to 3d46ccb1:c22f (+25ef) from 3d46ccb1:c259 (+2619)
>microtime leapt back to 3d46ccfb:731f6 (+606) from 3d46ccfb:73217 (+627)
>microtime leapt back to 3d46cd23:89ca6 (+1126) from 3d46cd23:89cc5 (+1145)
>microtime leapt back to 3d46cd23:8d9a1 (+1) from 3d46cd23:8d9d0 (+30)
>microtime leapt back to 3d46cd2b:3088b (+225b) from 3d46cd2b:308aa (+227a)
>microtime leapt back to 3d46cd2b:b93b7 (+2207) from 3d46cd2b:b93d7 (+2227)
>microtime leapt back to 3d46cd41:2c1b0 (+290) from 3d46cd41:2c1ce (+2ae)
>microtime leapt back to 3d46cd41:5e542 (+18e2) from 3d46cd41:5e561 (+1901)
>microtime leapt back to 3d46cd42:6aeab (+1efb) from 3d46cd42:6aecb (+1f1b)
>microtime leapt back to 3d46cdb4:72d1f (+12f) from 3d46cdb4:72d3d (+14d)
>microtime leapt back to 3d46cdcf:e876e (+87e) from 3d46cdcf:e878a (+89a)
>microtime leapt back to 3d46cdd0:be032 (+2062) from 3d46cdd0:be050 (+2080)
>
>The values are 'seconds:usecs (+time that microtime added on)'.
>
>My 'best guess' is that the errors happen when an interrupt is
>lost.  However I haven't traced the whether microtime() added
>10000us because in interrupt was deferred.
>(This ought to require that microtime be called with the timer
>interrupt disabled.)
>
>It is certainly possible to generate the errors my moving
>mozilla windows around the screen.
>
>	David
>
>  
>