Maker Pro
Maker Pro

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

M

Mike Foss

Jan 1, 1970
0
mike said:
Very often, the economic or political considerations
dwarf any technical consideration.
The technical explanation is that they do what's cheap.
Wishing for a grand technical reason won't make it so.
mike

You seem to be saying curiosity is a worthless trait.

I bet you're a republican.
 
D

Don Bruder

Jan 1, 1970
0
Andy Cuffe said:
I've always wondered why the batteries in macs run down so quickly. I
rarely see a PC newer than 10 years old with a bad battery, but I
consistently see 3-5 year old macs with totally dead clock batteries.

I'm not absolutely certain on that myself, though many explanations have
been put forth over the years, with the one I think is probably "the
real situation" being that Macs (A) Don't cut the battery out of the
circuit when powered up and (B) the battery isn't just keeping the RTC
running, but also keeping a chunk of memory (which we call "PRAM" here
in Mac-land - holds various fairly-to-really critical information) alive.
Macs even have a much larger (and more expensive) lithium cell than
most PCs. I've seen a few 15 year old 486's with the same type and
brand battery used by apple that still measures full voltage.

I don't know for certain about measured voltage, but I've only actually
*NEEDED* (as opposed to "shotgunning" a startup issue) to replace one
battery in my <stops to count> Hmmm... I guess that would be about 8
Macs over the last 15 years or so. That was in a Performa 637CD that I
picked up at a thrift store for ten bucks. The machine I'm typing on, a
PowerMac 7500, came to me secondhand also, and as far as I have any way
to know, it's still running on the factory-installed battery - 10+ years
since it came off the line.
 
M

mike

Jan 1, 1970
0
Mike said:
You seem to be saying curiosity is a worthless trait.

Nope, I'm saying insisting on technical explanations for economic
decisions is a worthless trait.
Anybody with a wrist likely understands that it's possible to keep
accurate time. If computer users rated it high in their purchase
decision, you'd see very accurate clocks.
It's all about the Benjamins...
I bet you're a republican.

I'll check my voter registration and get back to you.
mike




--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
 
M

Mike Foss

Jan 1, 1970
0
mike said:
Nope, I'm saying insisting on technical explanations for economic
decisions is a worthless trait.
Anybody with a wrist likely understands that it's possible to keep
accurate time. If computer users rated it high in their purchase
decision, you'd see very accurate clocks.

File that one under D for DUH.

The OP was asking for a technical explanation, and so far the
responses have been enlightening. Well, except for yours.
 
K

Ken

Jan 1, 1970
0
That question have been around for more than 20 years and probably
longer. Even one PC magazine reported a major branded PC that used to
cost $2,000 couldn't keep time as well as a $5 watch from Kmart (not
exact quote but similiar to that)

The OS could check via internet at regular intrevials to make
correction to the clock but that is if the PC does have internet
connection at all.


http://www.tucows.com/downloads/Windows/Internet/TimeSynchronizers/
 
M

mike

Jan 1, 1970
0
Mike said:
File that one under D for DUH.

The OP was asking for a technical explanation, and so far the
responses have been enlightening. Well, except for yours.
There is no technical explanation except that the technology that
is being used does not guarantee accurate clocks.

If you do the math, you'll uncover the fact that a wristwatch is
phenomenally accurate compared to a RTC crystal.

I haven't been responsible for a computer design since 1989. Back
in the day, the philosophy was, "design for the center of the
statistical distribution and fix it in software."
Fortunately, UINX was smart enough to do time correction.

I haven't been responsible for a frequency counter design group since
1975. Back in the day, the philosophy was, "use the cheapest timebase
that guaranteed the specified accuracy."

I've had motherboards where they saved a nickel by leaving off the two
caps on the Xtal. Adding the caps helped, but "net time" fixed it in
software.

Are we seeing a trend yet?
You can get any accuracy you're willing to pay for. Computer users have
voted with their wallets for "lousy". I don't remember ever seeing a
specification for real time clock accuracy on a motherboard.
So if the clock ticks, it's in spec. Statistically, you'll sometimes
get one that's unacceptable and some of those will get bitched about on
the internet. It's the same reason that sometimes your Ford won't run
right.

You're the Chinese engineer. Go tell the bean counter that you want to
add 20 cents worth of parts to adjust the clock frequency, add $4000
worth of capital equipment to each production station, a week of
additional production line time to setup and program the equipment,
30 seconds of operator time to each board test and decrease the overall
yield.

It really is all about the Benjamins.

Let me restate it in technical terms. You get what you pay for, if
you're lucky.

And yes, my motherboard keeps very good time (but still not anywhere
near as good as my wristwatch). It's not because the design is
different from any other motherboard design. It's because all the
variables conspired to keep good time. I got lucky.

Benjamins!!!

mike

--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
 
B

BillW50

Jan 1, 1970
0
Date: 26 Oct 2005 15:03:04 -0700
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.

Not one single person has mentioned that their computer keeps great
time. My first personal computer was back in '81 and it didn't even
sport a clock. Today I have collected about 16 computers (most of them
are in the closet). But the majority of them keeps very good time. Some
haven't been fired up in years, and it is really rare to find one off
more than 5 minutes. So I am at least one user who has been quite
happy with my computer clocks.

______________________________________________
Bill (using a Toshiba 2595XDVD & Windows 2000)
-- written and edited within Word 2000
 
Hi!
I've often wondered the same thing...also why a $9 alarm clock will have
provision for battery backup, but $200 VCR (back when VCRs were $200)
needed to be rweset with each blip in the mains voltage.

Hmmm...not all of them do. I've got a Panasonic VCR that will hold the
time for a couple of hours after a power failure and a Sony that seems
to be good for a few days. (Of course, both are 'mid-range' machines
and the Sony might qualify as lower high end equipment.)

I also have a Panasonic time-lapse VCR that has a NiCad battery in it.
I know it will the clock for at least two weeks. The manual says it
could last for a month.

William
 
Hi!

Is that a DS1387 or something else?

I've got some microchannel-based computers that use that module. None
have died yet but I know it is a matter of time.

How did you get the module open? Do you have pictures?

William
 
O

Ol' Duffer

Jan 1, 1970
0
FWIW, there are utilities which will update your computer clock from the
National Bureau of Standards over the web.....

They call themselves NIST these days, and they also still have
a dialup service.
 
Hi!
I've always wondered why the batteries in macs run down so quickly. I
rarely see a PC newer than 10 years old with a bad battery, but I
consistently see 3-5 year old macs with totally dead clock batteries.

Yep, I've seen the same thing here. I have a number of old Macs (6100,
6300, LC, 9600, SE/30) that still keep decent time on the
factory-installed batteries. Some of these have gotten to the point
where the machines need to be powered up somewhat often to keep the
settings intact.

By compare I have many a G3 CRT-type iMac around (the 2001 models,
350~500MHz) and almost all of them have had to have their batteries
replaced.

Looking at things I can see one difference. Most PCs new and old power
their CMOS RAM chips from the power supply when they're running. A
great many ATX systems seem to keep the CMOS RAM and clock running from
the ATX standby supply as long as it is running. Some older PCs also
have NiCad or NiMH batteries onboard along with the circuitry to charge
them when powered up.

I've investigated the Macintosh a little bit and it looks like the
clock/NVRAM battery is constantly pulled upon, even when the computer
is on. This could also shorten battery life.

William
 
Hi!
Not one single person has mentioned that their computer keeps great
time.

Okay then, I'll jump in here. I was just waiting for someone to say it.
:)

I am a collector and operator of the IBM PS/2 line of computers. I have
a lot of them and most are powered up and running fairly often. Some
run 24/7 as servers.

The clocks on these things are--for the most part--extremely accurate.
I synchronize the clocks on my computers by way of the 'net to one of
the many network time protocol servers in the world. The
synchronization happens at least once a week, sometimes more often. I
don't think I've ever seen one drift more than a second or three
between synchronizations. Of course, it does depend upon the health of
the clock battery. Most people never changed them during the lives of
these computers...so they still run, but are rather weak. I usually
replace them immediately just to avoid a leaking episode.

You can also use these computers as rather large and heavy digital
clocks--they have a flourescent display panel near the power switch
that is normally used for power on self test codes. Fortunately, it is
is user/software-addressable and can be misused in a variety of fun
ways.

http://www.walshcomptech.com/ps2/images/server95big.jpg

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. :)

William
 
G

GregS

Jan 1, 1970
0
Hi!


Hmmm...not all of them do. I've got a Panasonic VCR that will hold the
time for a couple of hours after a power failure and a Sony that seems
to be good for a few days. (Of course, both are 'mid-range' machines
and the Sony might qualify as lower high end equipment.)

I also have a Panasonic time-lapse VCR that has a NiCad battery in it.
I know it will the clock for at least two weeks. The manual says it
could last for a month.

William

I wanted to add, my alarm clock has a nicad battery backup, which
is why I bought it. Changing batteries is rediculous and expensive.
Why take the time and expense of changing batteries when a built
in nicad is all you need. I have also seen various VCR's that seem
to hold time for a certain period.

greg
 
G

GregS

Jan 1, 1970
0
Hi!


Okay then, I'll jump in here. I was just waiting for someone to say it.
:)

I am a collector and operator of the IBM PS/2 line of computers. I have
a lot of them and most are powered up and running fairly often. Some
run 24/7 as servers.

The clocks on these things are--for the most part--extremely accurate.
I synchronize the clocks on my computers by way of the 'net to one of
the many network time protocol servers in the world. The
synchronization happens at least once a week, sometimes more often. I
don't think I've ever seen one drift more than a second or three
between synchronizations. Of course, it does depend upon the health of
the clock battery. Most people never changed them during the lives of
these computers...so they still run, but are rather weak. I usually
replace them immediately just to avoid a leaking episode.

You can also use these computers as rather large and heavy digital
clocks--they have a flourescent display panel near the power switch
that is normally used for power on self test codes. Fortunately, it is
is user/software-addressable and can be misused in a variety of fun
ways.

http://www.walshcomptech.com/ps2/images/server95big.jpg

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. :)

William

I have seem many computers loose time, and a low battery seems
to increase the loss. An online computer can also be reset. There are programs which
sync to Universal Time, and networks, and even mail programs can
perform syncronization automatically.

greg
 
D

Dan Hollands

Jan 1, 1970
0
Making a accurate oscillator requires two key things
1. An accurate crystal (note stability is not the same as accuracy)
2. An oscillator circuit design that does not "pull" or otherwise change the
basic frequency of the crystal.

Clearly if you design a watch these are primary concerns, so even a cheap
watch is done well

For a computer this not a primary concern and I am sure there is a wide
range of accuracy in different models of computers depending on the amount
of attention paid to these issues. My current computer with an intel mother
board does keep could time.

Dan

--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
[email protected]
www.QuickScoreRace.com
 
M

Michael Black

Jan 1, 1970
0
Don said:
I'm not absolutely certain on that myself, though many explanations have
been put forth over the years, with the one I think is probably "the
real situation" being that Macs (A) Don't cut the battery out of the
circuit when powered up and (B) the battery isn't just keeping the RTC
running, but also keeping a chunk of memory (which we call "PRAM" here
in Mac-land - holds various fairly-to-really critical information) alive.

That second means nothing in itself. "IBM PC" type computers have a tiny
bit of static RAM to hold the bios settings. If it wasn't there, and kept
alive, you'd always have to set those things every time you turn the computer
on.

Now, it may be that one uses more current than the other, but I can't
really see that being a significant difference.

Michael
 
I

Impmon

Jan 1, 1970
0
Not one single person has mentioned that their computer keeps great
time. My first personal computer was back in '81 and it didn't even
sport a clock. Today I have collected about 16 computers (most of them
are in the closet). But the majority of them keeps very good time. Some
haven't been fired up in years, and it is really rare to find one off
more than 5 minutes. So I am at least one user who has been quite
happy with my computer clocks.

There are probably more PC with good clocks than cheap inaccurate
clocks. The reason we rarely saw such posts are because people
usually complain loudly if their product is a bit "off" for any reason
and not many post positive comment on their product.

If everyone were to post every reviews, the bad one would get buried
in a hurry.
 
w_tom said:
Watches have an internal capacitor to adjust for each
crystal. I have never seen that capacitor on motherboards
since (I believe it was) the IBM AT. Furthermore, the PC
clock operates at two significantly different voltages that
will change crystal frequency. Battery voltage and voltage
when PC is powered will cause additional fluctuation. Which
voltage should they adjust the capacitor to? Just easier to
not install and adjust the capacitor.

I have an ancient Seiko quartz with a trimmer inside, and by adjusting
it I was able to make it accurate to 30 seconds a year. But few cheap
watches have them, including none of those I tried in this test.
 
W

w_tom

Jan 1, 1970
0
There are two ways to do as suggested. The first is to make
'Benjamins' part of the technical facts during design. The
second is to do the design, then let bean counters change the
design per what they 'feel' is not worth the bucks. The
latter is too often how GM cars are designed. Which is why a
GM car needs two extra pistons to get the same horsepower as
the competition. Which is why GM cars even in the 1990s
required annual wheel alignment. Which is why GM cars would
have what appeared to be computer failures when failure was
really due to cheap connectors. Classic examples of failures
when the design is modified after the design.

Two examples: how 'Benjamin' decisions become part of a
successful design verses how 'Benjamin' decisions after
application of technical facts makes bankruptcy.

Meanwhile, the technical reason for high verses low accuracy
timers was provided. Computer motherboards don't have the
trimming capacitor and the oscillator is subject to wider
voltage variations. Why this technical decision was made was
not asked and would only be speculation.
 
A

Andy Cuffe

Jan 1, 1970
0
ways.

http://www.walshcomptech.com/ps2/images/server95big.jpg

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. :)

William

IBM did a lot of things wrong with their PCs in terms of performance,
upgradability and user friendliness, but their quality was second to
none un until the end of the PS/2 line.
Andy Cuffe

[email protected] <-- Use this address until 12/31/2005

[email protected] <-- Use this address after 12/31/2005
 
Top