every 5 seconds, slick lag any ideas?

[booyah]

In windows I can watch my system clock, and every 5 seconds there seems to be like a 50ms lag.. I also notice it when undoing rar files.. the miliseconds lag once and awhile.. any idea what would cause this?? I have a 1.8ghz p4, with a gigabyte ga-8pe667 mobo.. got big fans.. cpu has been over clocked to 2.4ghz, but I clocked it down and it still happens.. could it be ram? thanx hope someone knows what would cause this.

[bigH2O]

You can notice a 50ms lag while watching your system clock? Wow. 50ms is 1/20th of a second. Talk about watching the clock! You must be in middle management somewhere.

Seriously though, your clock is managed by the clock crystal on the motherboard. This crystal oscillates at a particular frequency, and the number of wiggles of the crystal is used by the bios to keep the system time accurate. It really has nothing to do with whether you've overclocked the processor or the ram. If you're noticing lags in the clock, you're not actually noticing time standing still, you're noticing delays in the OS getting around to updating the clock. Events are assigned a priority by the OS. Updating the clock is an event that takes very little processor time, however it is a re-occurring event that were it assigned a high affinity in the pecking order, would cause noticable delays in applications. So the refresh of the clock is on the bottom of the totem pole as far as priority goes. If time comes to update the clock and the processor is busy doing something else, the clock doesn't get updated until the next time the processor gets a break. No big deal. The time isn't off, the system just isn't refreshing the display accurately.

Usually your clock crystals are fairly accurate, but they all depend on the accuracy of the frequency of the power supply coming into the box. If your power isn't running exactly at 60Hz (or 50Hz for our European friends), then the clock will vary by the amound of discrepancy in the expected cycle frequency of the supply times the multiplier frequency of the clock crystal. The higher the frequency of the crystal, the more accurate the clock will be.

Sometimes you'll get a clock crystal that is badly out of tolerance, and that will cause your clock to drift. I had a system one time that would lose 7 minutes of time over a 24 hour period. In that case, it was such a significant amount of time variation that I couldn't live with it and had to find a way to keep my clock updated without user intervention. I found a really good utility for setting the clock from here (http://www.arachnoid.com/abouttime/) for keeping the clock updated. It connects to one of several "official" time sites... mostly government and educational facilities that use atomic clocks to keep accurate time. It grabs the time off of the site it connects to, then calculates the round trip time for the connection, and sets your computer clock to the precise time. It's a very small unobtrusive application which can be set up to run as a silent re-occurring event in Windows. I have it set up to run every night on one of my servers, and use that box as a time server to update all the other computers. On that old PC with the bad clock crystal, I had it set up to run twice an hour, and never even noticed it running other than my clock quit losing time.