Why aren't computer clocks as accurate as cheap quartz watches?

[DBLEXPOSURE]

Why do the battery powered clocks in personal computers tend to keep
worse time than quartz watches, even the $1 ones?

The computer batteries measure fine, at least 3.15V.

I thought that the problem was temperature swings in the computers
(25-38C), but a couple of cheapo watches taped inside the computers
kept better time.

Because the processor in your computer might hang or busy itself with other
things besides keeping time. It may also have something to do with the
clock pulses your computer uses not being exactly divisible into real time.

look for a program called D4. It is a free download and will keep your
clock synced to universal time. Also, Widows XP can sync to the same time
servers that D4 uses. Both work great!

 

[w_tom]

Why so many "it might be this" or "it might be that" or
"time is updated from the internet"? Every posts says nothing
useful AND does not answer the OPs question. OP even
clarified the question when some replies were rubbish.

The answer -- technically -- was posted without
speculation. Processor hangs obviously do not affect that
clock operation - it one first learned how something works
before posting. The OP posted this - a technical question
that required technical knowledge before replying:

Why do the battery powered clocks in personal computers tend
to keep worse time than quartz watches, even the $1 ones?

See that word "might" ? That word "might" means the poster
does not know the answer and therefore should not have
posted. Anyone can speculate. But even worse, he posted
without reading the answer that was already posted. He did
not read every previous post before replying. A program
called D4 is equivalent to telling us when that mountain will
fall - not relevant to the OP's question. Most replies were
just as useless as this one. Why? How can so many post when
they never bothered to first learn how a computer's battery
powered clock even works?

 

[DBLEXPOSURE]

Who the hell made you the NG God who should say who should and who should
not post a reply. In short, **** You!

Don't tell me that the time kept by your computer does not require a
processor and that it does not ever hang because that is bullshit.

The fact that the OP asked the question leads me to assume that his clock on
his computer not keeping accurate time is annoying him. Therefore, I
recommended the Program called D4. It is a solution to the problem and it
works.

 

[DBLEXPOSURE]

Why so many "it might be this" or "it might be that" or
"time is updated from the internet"? Every posts says nothing
useful AND does not answer the OPs question. OP even
clarified the question when some replies were rubbish.

The answer -- technically -- was posted without
speculation. Processor hangs obviously do not affect that
clock operation - it one first learned how something works
before posting. The OP posted this - a technical question
that required technical knowledge before replying:

See that word "might" ? That word "might" means the poster
does not know the answer and therefore should not have
posted. Anyone can speculate. But even worse, he posted
without reading the answer that was already posted. He did
not read every previous post before replying. A program
called D4 is equivalent to telling us when that mountain will
fall - not relevant to the OP's question. Most replies were
just as useless as this one. Why? How can so many post when
they never bothered to first learn how a computer's battery
powered clock even works?

What Happens and Why
There is a "CMOS clock" in your computer which is powered by a tiny battery.
As long as the battery is good, this clock keeps the correct time, and each
time your computer is restarted, Windows98 reads its initial time from the
CMOS clock. However, while Windows98 is running, it keeps track of the time
on its own without continuing to check the CMOS clock, and keeping track of
the time is not the only thing Windows has to do. The busier your system
gets, the more likely it is to lose time. Generally, the longer you use your
computer, the further behind it gets. When you leave your computer on for an
extended amount of time, the Windows clock (displayed on the taskbar) may
lose from two minutes to an hour per day.

Likely culprits
Anything that makes your computer especially "busy" can take Windows'
attention away from its time-keeping function and lead to this "losing time"
symptom. If you're running lots of programs, or even just one or two very
demanding programs, you may see the computer clock losing time. Furthermore,
anything you are running which causes the computer to have to spend time
"watching" for something to happen can also lead to a slow clock. Here are
the most common culprits:

a.. Games and other video-intensive programs

b.. Screen savers and "scheduling" programs

c.. Internet chat programs (ICQ, IM, etc.)

d.. Playing MP3 files, CDs, or internet audio

e.. Anti-virus programs

f.. Processor-intensive applications

 

[James Sweet]

Why so many "it might be this" or "it might be that" or
"time is updated from the internet"? Every posts says nothing
useful AND does not answer the OPs question. OP even
clarified the question when some replies were rubbish.

The answer -- technically -- was posted without
speculation. Processor hangs obviously do not affect that
clock operation - it one first learned how something works
before posting. The OP posted this - a technical question
that required technical knowledge before replying:



See that word "might" ? That word "might" means the poster
does not know the answer and therefore should not have
posted. Anyone can speculate. But even worse, he posted
without reading the answer that was already posted. He did
not read every previous post before replying. A program
called D4 is equivalent to telling us when that mountain will
fall - not relevant to the OP's question. Most replies were
just as useless as this one. Why? How can so many post when
they never bothered to first learn how a computer's battery
powered clock even works?

Why is speculation useless? Nobody can give one solid answer because the
problem is not identical across all computers, nor is it always caused
by one simple factor. I've learned a fair amount of interesting things
from this thread, I guess you missed all that.

 

[DBLEXPOSURE]

Right on James!

That is how the NG's are suposed to work. But you get these trolls who
think there answer is the only answer. They have closed minds.

 

[JAD]

Why so many "it might be this" or "it might be that" or
"time is updated from the internet"? Every posts says nothing
useful AND does not answer the OPs question. OP even
clarified the question when some replies were rubbish.

The answer -- technically -- was posted without
speculation. Processor hangs obviously do not affect that
clock operation - it one first learned how something works
before posting. The OP posted this - a technical question
that required technical knowledge before replying:

And your answer was? or were you just posting to post.

See that word "might" ? That word "might" means the poster
does not know the answer and therefore should not have
posted. Anyone can speculate.

In this environment speculation is just about all you have as the machine
(subject) is rarely in your hands. Since then a phrase has been invented to
take the place of that....and that would be...YMMV


But even worse, he posted

 

[DBLEXPOSURE]

Just in case anybody is interested

http://www.thinkman.com/dimension4/index.htm

And for the record, Tom, is relevant to the OP's question because it
concerns your PC's clock keeping accurate time. It is a solution to the
problem. What have you to offer?

 

[Rick Yerger]

Just in case anybody is interested

http://www.thinkman.com/dimension4/index.htm

And for the record, Tom, is relevant to the OP's question because it
concerns your PC's clock keeping accurate time. It is a solution to the
problem.

That wasn't the question. The OP didn't ask how to solve
the problem.

 

[DBLEXPOSURE]

That wasn't the question. The OP didn't ask how to solve
the problem.

So what? I had offered an answer to that as well as offering a solution.
Perhaps you didn't read that part of the thread.

Now, Had I said your pc's clock will run slow because magic trolls and
ferries sneak in make adjustments to the master oscillator. That might
warrant an attack. But the rest of this crap is just that, crap!

you see my mind is not one dimensional, I might take a question and expound
on the answer to not only give a reason why this happen but also offer a way
to correct it.

And by the way, my last comment was prefaced, "Just in case anybody is
interested". Obviously you are not so the post was not intended for you.
In other words, Bug Off, pedal on and get a life!

 

[w_tom]

Your other post is classic of those who use emotion as if
emotion was logic. I will pretend you did not post an
outburst in the other post; in respect for your dignity.

Below is a partial description of how the computer's other
clock works. It assumes time lost will also cause the
computer's battery clock to change. Do you know they both use
completely different circuits and oscillators (time bases)?
That battery clock does not change no matter how many seconds
or days the Windows (Operating System) clock changes.

This might be true if the system is not pre-emptive
multitasking or if the OS itself crashes - which is rare
enough to not be relevant:

The busier your system gets, the more likely it is to lose time.
Generally, the longer you use your computer, the further behind
it gets. When you leave your computer on for an extended amount
of time, the Windows clock (displayed on the taskbar) may lose
from two minutes to an hour per day.

Meanwhile, as an OS gains or loses time, the computer's
battery clock remains unaffected. Again, you should have
known this which is why your original post used the word
"might". Well, at least this time you look up some facts
before posting. But you did not obtain all facts. Loss of
time by the OS does not change the CMOS or battery clock.
Made obvious with simple hardware or BIOS knowledge. You are
advised to first learn the basic circuit - as it was designed
even in the original IBM AT. The circuit is based in a famous
IC - Motorola's MC146818 and an equivalent IC from Dallas
Semiconductor.

Not knowing how this battery clock works is not what you are
criticized for. Furthermore an emotional outburst was not
posted - a lesson you should learn from. Criticism is based
on facts. You posted speculation AND you posted things
totally irrelevant to what the OP was asking. Not just you.
This thread is chock full of posters who only speculated and
who did not answer the OP's question.

Now you are also being corrected for not learning all the
facts about how the battery backup data time clock works.
Your "Likely culprits" list is not based on knowledge of a
1984 legacy circuit that is standard in PCs. Gain or loss of
time by the OS - using a completely different clock - does not
affect the battery backup clock. This true in hardware today
as it was in the original IBM AT. Those "most common
culprits" in no way change the date time of a battery backup
clock.

What was do_not_spam_me asking? He was asking about that
battery backup clock also known as the CMOS date time chip -
which is unaffected by and unrelated to your "most common
culprits". IOW again, the answer is not based upon the OP's
original question.

 

[Ol' Duffer]

If you're gonna nitpick...

Why so many "it might be this" or "it might be that" or
"time is updated from the internet"? Every posts says nothing
useful AND does not answer the OPs question.

You apparently didn't read *all* the replies, but more to your
question, a lot of people with too much time on their hands and
too little knowledge to be useful feel compelled to type when
you put a keyboard before them. Must be an ego thing...

See that word "might" ?

No, I don't. Where do you see it?

But even worse, he posted without reading the answer that was
already posted. He did not read every previous post before replying.

UseNet is arcane and slow, so messages may take hours or even
days to propagate through the system. In some cases, it is
even possible to see replies before the original question.
You cannot tell much about what posts someone else has seen
from the time of appearance on *your* screen.

 

[[email protected]]

The only bad thing about these is that these PS/2s make the clocks in
almost all of my other machines look like a sad joke.

Could you have a look into how these clock are constructed.. ?

 

[w_tom]

The battery backup circuit in a PC is a circuit originally
in IBM AT - a legacy of that well established 1984 design
using a Motorola MC146818.

To have posted as DBLEXPOSURE has, he should have first
known about that circuit. A majority of posts in this thread
are total speculation based upon no relevant technical
knowledge. That is shameful if not irresponsible. One even
claims the OS clock causes changes in a completely different
oscillator - the CMOS date time clock. Again, one who did not
first learn basic facts. Unfortunately too many people (often
who are only programmers) somehow become experts on how
hardware works. Had he even learned a PC's BIOS, then this
would have been obvious.

DBLEXPOSURE demonstrates that many just know; cannot bother
to first learn how hardware works. It is the difference
between one who is product oriented (deals in reality) and the
antonym of a product person - the MBA. DBLEXPOSURE posted
wild speculation - even worse doing so without first reading
a previously posted and technical answer. Two problems in his
response are cited. But then he adds a third problem: learns
only half of how a CMOS date time clock works; speculates that
timing changes in the OS changes a date time clock.

First what he (and others) originally posted in response to
do_not_spam_me's original question has nothing to do with the
question asked by do_not_spam_me. Second, many of those posts
all but admit they don't know - based in wild speculation.

At least, in a later post, DBLEXPOSURE attempts to learn how
the CMOS date time clock works. But he still got it wrong.
Those applications - "Likely culprits" - will not affect the
battery backup CMOS date time clock. He should have known
that even from facts that an inquisitive user observes.

BTW, Rick Yerger also criticizes DBLEXPOSURE for not
answering the question. Rather than act product oriented,
DBLEXPOSURE replies as an MBA:

Bug Off, pedal on and get a life!

Again he demonstrates no grasp of facts - instead using
feelings as if his feelings were facts. I don't have anything
to apologize for when I criticize what DBLEXPOSURE and others
have posted. Wild speculation was misrepresented as fact -
and did not even answer do_not_spam_me's question.

Two factors cause significant variation of the CMOS date
time clock. No trimmer capacitor and a timer that varies due
to different voltages.

 

[[email protected]]

Why do the battery powered clocks in personal computers tend to keep
worse time than quartz watches, even the $1 ones?

The computer batteries measure fine, at least 3.15V.

I thought that the problem was temperature swings in the computers
(25-38C), but a couple of cheapo watches taped inside the computers
kept better time.

The answers I found useful in the thread are:
* Use internal capacitor to adjust for the crystal.
* Provide stable voltage.
* DS1387 (suns?) have a good track record.
* Crystal chassi shall be grounded.

Useing these facts it should be possible to construct a fairly precise clock.
A precise crystal with internal capacitor in shielded box powered by it's
own linear voltage regulator should do it?

It could then countup a synchronous counter on positive flank. And be read on
negative flank (and only then).

Regulator could use diodes to enable proper batteri/psu operation. Separate
regulator for counter and crystal.

 

[[email protected]]

If there was an answer in this thread, I must have missed it. So many
ideas, so few applications of the facts

There are two clocks in a PC (I don't know MACs) A hardware one, and the
software clock. When the PC boots, the BIOS reads the hardware clock, and
the OS asks the BIOS what time it is. From there on, good old windows or
whatever is doing the clock counting, using an interrupt timer. Given the
sloppy programming, and the inability of windows to pre-emptively
multitask, the software clock is not going to be very accurate. Just open
your time settings screen and watch the second hand on the clock. That
will show you right away that not only is windows terribly inefficient, it
is unable to update the clock consistently, and accurately, even when it
is 'idling,' due to system overhead, poorly implemented.

Each time you power down or restart the PC, the hardware clock is read,
and it is more accurate than the software, although still subject to
crappy crystals and poorly implemented devices. If you leave the computer
on for days at a time, a restart will probably get the clock back to a
more accurate setting, but not necessarily much better.

The question of why the PC clock is so inaccurate, and yet more expensive
than a cheapo watch is simply a matter of "how ya gonna get the
information out of the cheap watch, and into the PC?" The clock itself,
and the crystal are only a portion of the hardware required by a PC to
know what time it is. The additional requirements increase the sicon die
size, as well as the complexity of the design, so the higher cost is to be
expected. If you can get the time out of a cheap watch, in binary form, at
the proper levels, and the proper timing specs, without raising the price
of the $1 watch, a lot of people would like to hear from you ;-)

There are many sources of RTC boards that plug into a PCI slot and take
over the timekeeping for highly accurate applications, and of course, as
so many pointed out, apps the use the National Standards are free and easy
given net access.

Just another 3.5 cents.

Mark

 

[David Maynard]

The answers I found useful in the thread are:
* Use internal capacitor to adjust for the crystal.
* Provide stable voltage.
* DS1387 (suns?) have a good track record.
* Crystal chassi shall be grounded.

Useing these facts it should be possible to construct a fairly precise clock.
A precise crystal with internal capacitor in shielded box powered by it's
own linear voltage regulator should do it?

It could then countup a synchronous counter on positive flank. And be read on
negative flank (and only then).

Regulator could use diodes to enable proper batteri/psu operation. Separate
regulator for counter and crystal.

Sure its possible to make an 'accurate' hardware clock, and plenty exist,
but there isn't a compelling reason to be obsessive about it for a
'typical' PC as it is either of little consequence (like a standalone PC)
or there is a more convenient solution such as domain/internet time
synchronization.

And domain time synchronization would be needed even if every PC in the
domain had an 'accurate' (however we define that) clock because there are
too many ways even an 'accurate' clock can get off time, not the least of
which being that 'time', when running, is different than the CMOS clock.

Its really more complex than just the CMOS clock as that clock isn't what a
PC really needs. A computer needs a regular interrupt to schedule tasks and
do other time keeping functions so you end up with the situation where the
'software' time doesn't match the 'hardware' time, regardless of how
'accurate' the CMOS clock is, and contrary to w_tom's global assertion that
the software time doesn't affect the CMOS clock it depends on the O.S..
Modern Linux systems (e.g. Debian 2.2 and up), for example, set the CMOS
clock to the software clock at shutdown so they're synchronized.

At any rate, you'd end up going through the pain of trying to make a
blisteringly accurate CMOS clock simply so it's blazingly accurate at post
rather than waiting a minute for it to synchronize after boot and network
access comes up. Is that worth it?

 

[David Maynard]

If there was an answer in this thread, I must have missed it. So many
ideas, so few applications of the facts

There are two clocks in a PC (I don't know MACs) A hardware one, and the
software clock. When the PC boots, the BIOS reads the hardware clock, and
the OS asks the BIOS what time it is. From there on, good old windows or
whatever is doing the clock counting, using an interrupt timer. Given the
sloppy programming,

and the inability of windows to pre-emptively
multitask,

Incorrect.

<snip>

 

[James Sweet]

D

Incorrect.

<snip>

How about offering some insight rather than just a big buzzer?

Depends on the version really, Win 3.1 and earlier didn't offer
pre-emptive multitasking, when an application was minimized it generally
ground to a halt. Win 9x was a big improvement over this but still
mediocre. Win NT/2K/XP is better still, and are generally quite good
OS's, but the multitasking is still rather poor compared to several
other OS's on the market. Of course any OS is a compromise, what you
gain in one area you often lose in another.

 

[[email protected]]

A long time ago, I regularly had good luck by substituting crystals
taken from watches, but when I tried the crystals from computer clocks
in some of those watches, their accuracy would worsen considerably.
And crystals I bought from parts suppliers were so bad that I switched
to getting my crystals from stick-on clocks for cars

A National Semiconductor note for one of their clock chips mentioned
that common crystals varied from 1-100 ppm accuracy per year (~30 secs.
to almost 1 hour), the worst by far being those sealed with solder, the
best sealed in glass or without heat.