BOOT CAMP 308 (12/01/04)
As so often happens this
week’s topic was inspired by reader emails, two of them to be precise, though it
was the lack of precision that sparked the whole thing off.
It wasn’t so much the
content of the emails that caught my eye but the time and date they were sent.
The first was apparently written four years ago, on January 1st 1999, which
stretches credulity somewhat, even with the Internet creaking under a deluge of
Spam. The second email was even more remarkable as it bore the date June 2006.
The message referred to a previous week’s Boot Camp and I concluded that it
probably wasn’t from the future, though I emailed the sender for a list of
forthcoming Lotto numbers, just in case…
The ‘sent’ time and date
stamp on an email is determined by the PC on which it originated and it’s
interesting to see how many computer clocks are set wrongly. A random survey of
the sent times of emails in our inbox suggests that at least half of Connected
reader’s PCs may be more than five minutes adrift. You can check the accuracy of
your PC clock (to the nearest second) by going to: http://vancouver-webpages.com/time/.
Normally it doesn’t
matter too much if the clock on home PCs run a little fast or slow, in fact it
is inevitable due to the way most computers keep track of time. The worst that
usually happens is emails and saved files are incorrectly time-stamped. However,
accurate timekeeping can be vitally important on PCs used to keep business
records or conduct financial transactions, but in any case it is worth knowing a
bit about how PCs keep track of time, and what you can do to improve accuracy.
PCs have two clocks; the
first is the hardware or ‘real-time clock’ (RTC), a small battery powered module
on the motherboard that maintains timekeeping when the PC is switched off,
disconnected from the mains or a source of power. It is controlled by a quartz
crystal and accuracy can easily wander by 10 to 15 seconds a day due to
variations in temperature. The battery powering the clock generally lasts for
between 3 and 5 years and towards the end of its life the clock will slow down
or become erratic. Look out for warning messages at boot up, including the
really helpful ‘CMOS checksum invalid’, and ‘Invalid configuration run
Setup’. Replacing the clock battery is not usually too difficult, and they
normally only cost a pound or two but seek expert help if you don’t fancy the
idea of opening up your PC.
The second PC timekeeper is the ‘software’ clock, which is
built into Windows. At boot up Windows receives data from the RTC to set the
clock and then uses system timing signals to keep the display clock ticking. The
accuracy of these timing signals varies, depending on what else the PC is doing.
Clocks on older PCs using early versions of Windows could loose several minutes
a day just by running a couple of applications. Accuracy improved dramatically
from Windows 98 onwards and the clock in Windows XP is largely unaffected by the
PC’s workload, nevertheless, the time on all standalone PCs can and does drift
if the only source of reference is the RTC.
There are several ways
of ensuring that your PC clock is correct. You can set it manually from an
external time signal, such as the ‘pips’ on the radio, the Speaking Clock or
Teletext but this can become tedious if you have to do it every day. There used
to be a range of gadgets, like super-accurate temperature–compensated clocks and
‘MSF’ radio time receiver modules but these days the best way to ensure accuracy
is to log on to a ‘Network Time Protocol’ (NTP) server on the Internet. These
are web sites that provide highly accurate time and date information derived
from atomic clocks. Delays and errors introduced by the Internet, including the
distance between the PC and time server, can be compensated for and it’s
possible to ensure that your clock is never out by more than a second, as well
as checking and correcting for any errors in the PC’s date settings.
Windows XP has an
Internet time facility built in. When online double-click the clock display,
select the Internet Time tab, click the Update button and Windows checks and
synchronises the clock with the two default NTP servers (for a list of
alternative time servers go to: http://www.ntp.org/). After than XP
automatically checks the time once a week. For a list of Internet time sync
utilities for earlier versions of Windows see Tip of the Week.
Next week – Transferring Outlook Express
By analysing the
vibrations of certain atoms (Cesium is the favourite) it is possible to measure
time to an accuracy of a few billionths of a second per
metal oxide semiconductor - family of low power microchips used to store and
process digital data
MSF RADIO TIME
The call sign of a radio signal containing time and date
codes, generated by an atomic clock, broadcast by the UK National Physical
Laboratory near Rugby on a frequency of 60kHz
TIP OF THE WEEK
There are a number of
utilities for Windows 9x (95/98/ME/SE), to check and correct your PC clock and
date settings every time you log on to the Internet or at scheduled intervals.
The freeware offerings are often just as good and in some cases even better than
the commercial programs so have a look at: Time Synchronizer (http://www.itoolpad.com/products/timesync/), DS Clock (http://www.dualitysoft.com/dsclock/) and SymmTime