Does XP by itself write the OS time to the Real Time Clock (RTC)???

[Mike]

Hi, I have a question about Microsoft's OS.

My question is in relation to an stand alone computer with
no network connectivity except dial-up.



QUESTION 1:
Without the user's manual interference does Windows XP
(without SP1) at any time by itself, e.g. when restarting,
write the Operating System Time or CMOS Time to the Real
Time Clock (RTC)???


QUESTION 2:
Without the user's manual interference does Windows 98SE
at any time by itself, e.g. when restarting, write the
Operating System Time or CMOS Time to the Real Time Clock
(RTC)???



Thank you,
Mike.

 

[I'm Dan]

My question is in relation to an stand alone computer with
no network connectivity except dial-up.

Without the user's manual interference does Windows XP
(without SP1) at any time by itself, e.g. when restarting,
write the Operating System Time or CMOS Time to the
Real Time Clock (RTC)???

Without the user's manual interference does Windows
98SE at any time by itself, e.g. when restarting, write the
Operating System Time or CMOS Time to the Real Time
Clock (RTC)???

Think about your question for a moment. When the operating system is
starting up, how would it know the time? It doesn't, so there isn't any
"operating system time" to write to the RTC. The RTC (aka, the CMOS
clock -- they're one and the same) is the hardware component that knows what
time it is because it keeps running when the system is turned off. When the
OS boots, it does not know the time, so it queries the RTC to get the
date/time and initialize the system clock (which runs in RAM). Thereafter,
the system clock and RTC run independently (and may not even stay in synch
if either doesn't keep time accurately).

Normally, the system clock will not write to the RTC unless you manually
edit the system date or time. Then the system updates the RTC immediately.
However, note that XP includes a background process that tries to synch the
system clock with an internet time server every so often (by default, once a
week, I think). If it successfully does so, it probably updates the RTC at
the same time. Does that meet your definition of "without manual
interference"?

 

[Stephan]

Not by itself, no.
If one remembers any of the MS-DOS batch file commands,
one could set the time / date within a batch file,
but this would end up with the same time over and over.

 

[Mike.]

Thanks "I'm Dan" <[email protected]> for your
reaction.

First of all the CMOS clock and RTC are NOT the same at
all as you state.

A PC has 3 clocks (NOT 2):
-RTC
-CMOS CLOCK
-OS CLOCK (this is the time the OS is indicating whist
running)

At POST the RTC initialises the CMOS clock.
When the OS starts the CMOS clock initialises the OS clock.
Thereafter both the CMOS clock and OS clock run
independantly fom eachother and from the RTC. After POST
the RTC is never updates the CMOS time until the next
reboot.

My original post was:

Without the user's manual interference does Windows
98SE at any time by itself, e.g. when restarting, write the
Operating System Time or CMOS Time to the Real Time
Clock (RTC)???

When I used the words "when restarting" in my initial post
I did not mean the period the OS starts but instead the
period the system shuts down to perform a restart .
Sorry for the confusion.

To me and a big brand computer service man it appears XP
upon e.g. shut down writes its (usually incorrect)OS time
to the RTC.


My definition of without "manual interference" is:
OS writes to RTC without the user manually entering the
date/time settings GUI or in any other way influences
writing to the RTC (by e.g. using a batch file).


So anyone with XP insight know if XP writes OS time or
CMOS time to the RTC at any point, e.g. at system shutdown?
It is really important for me to know for sure.

If I reboot XP e.g. 10 times, my RTC is suddenly some
seconds behind. E.g. 7 seconds!!!!
(The RTC is 100% ok and before booting 10 times in XP is
indicating the precice time.)

Please note my internet sync is off.

Please note that I have a clean install of XP running
witout SP1.

XP is runnign on a notebook.

It is a dual boot system using BootStar as the bootmanager.


Anyone???


Thanks in advance.

Mike.

 

[I'm Dan]

First of all the CMOS clock and RTC are NOT the same at
all as you state.

A PC has 3 clocks (NOT 2):
-RTC
-CMOS CLOCK
-OS CLOCK (this is the time the OS is indicating whist
running)

At POST the RTC initialises the CMOS clock.
When the OS starts the CMOS clock initialises the OS clock.

Okay, that I didn't know. Not sure I see the reason for that, but it's been
years since I've had occasion to circuit-trace anything new, so I'll take
your word for it. All the systems I've circuit-traced in the past (at
least, after the 8088 and AT) used a single IC chip with the RTC embedded in
the same chip as the CMOS setup data.