Accurate Time For Your Computer

Computers maintain time even when powered off by using a battery backed real-time clock. The clock chip uses a quartz crystal as a time reference in exactly the same way as your watch keeps time. However, with the highly competitive mass-production of PC’s, component costs have tumbled. This has resulted in low-cost, sometimes inferior components being used in the manufacture of PC’s. Therefore, many computer clocks are notoriously poor at keeping time. We have come across some computer clocks losing minutes each day.

If your computer systems are used for any form of time stamping, such as data logging or transaction processing, this can cause real problems. Time stamps generated by different computers at the same time can log differing and often inaccurate times. In such circumstances, network time synchronization is a must.

Luckily, there are well-established solutions to these problems:

Internet Based Time References

Probably the most cost-effective way to synchronize a computer network is to use an internet based time server. There are a number of Network Time Protocol (NTP) servers available across the internet that can be used. Using NTP or SNTP client software, simply point your computer to the IP address or domain name of a time reference and it will periodically synchronize. However, there are a number of disadvantages associated with internet time references. Firstly, your network needs to have access to the internet. There are security implications of leaving ports open in your firewall. Additionally, many internet based time references are miss-configured and there have even been cases of them provided an incorrect time.

Local Hardware Clocks

An alternative source of time is a GPS or radio based hardware clock. These are hardware devices that can obtain accurate time from GPS or radio time references and provide an accurate source of time to a PC. The devices generally have RS232 serial or USB interfaces and are provided with driver software that can synchronize a PC’s system time to the hardware clock. These devices are more secure, since an internet connection is not required. Additionally, a very precise time can be obtained from hardware clocks, with very little latency due to close-coupled connectivity. However, these devices do require additional software to be installed on a computer, which does add a small processing overhead. Also, they will only synchronise a single computer rather than a network.

Local NTP Time Servers

A local NTP time server combines the advantages of a local hardware clock with network-wide availability. They use GPS or radio time references to provide a network with a source of accurate time. Any device attached to the network can synchronize time. Additionally, since most operating systems, including Microsoft Windows and Linux, have build-in NTP\SNTP clients, no additional software is required.


About the Author.
Andy Shinton has spent his entire career within the IT industry, mainly in the Time and Frequency sector. Since 2002, he has headed TimeTools Research and Development Division. Andy regularly writes white-papers and articles about NTP and Network Timing Solutions.
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