I'm not sure. I can only tell you that DOS has it's own clock device.
Checkit! (v3, for example) has got a clock testing part, some Y2K test programs have it, too.
Maybe the Real Time Clock or the system timer is faulty ? Perhaps it just a defective crystal (xtal) on the mainboard also, who knows ?

Edit: Also try the System Board test. Shouldn't hurt..

i tried it and the real-time clock test immediately failed. but i am not good at hardware repairing so which component is the real-time clock? or which oscillator is related to it?
i'll upload a picture of the board soon after i remove the cards.

Had this happen on a 286 board, sometimes doing a few years in a single day. On the oscillator input of the RTC I measured between ~160kHz and a few MHz. The 32.768kHz crystal was defective.

my board is identical to this one(which has its bios socket emptied to reveal a chip under it):
download/file.php?id=56933&mode=view
can you tell me which component is the RTC and which oscillator works with it?

It's the part marked Y1, a small metal cylinder next to the keyboard controller with AMIKEY logo.

EDIT: That's the crystal resonator you should replace (or test if you have a scope). It'll be connected to that 4069 below it, and that in turn will feed a MC68HC68-like chip, that'll be the RTC itself.

Deunan wrote:

It's the part marked Y1, a small metal cylinder next to the keyboard controller with AMIKEY logo.

EDIT: That's the crystal resonator you should replace (or test if you have a scope). It'll be connected to that 4069 below it, and that in turn will feed a MC68HC68-like chip, that'll be the RTC itself.

thanks for the info. however i don't see any MC68HC68-like chip on the board, almost all the chips i can see are 74-series logic gates. could it be integrated in that um82c493f chip which seems to be an io controller chip? could't find any info on it and the um82c491 chipset though.

Oh sure, if there is no external RTC then it's integrated into the chipset.

Yes, it could also be integrated. Though I believe that externals oscillators are more likely to fail. Not because of differences in quality, but mechanical stability.
Oscillators or resonators inside these little metal cases can break if they are exposed to strong mechanical stress (vibration).
Just to besure, I marked all of the oscillators that I saw on the picture.

Dunno which oscillator is responsible in this case.
Original PC had no RTC, derived its time from the 18.2Hz tick generated from the 14.318MHz system clock.
Could even be a problem in the clock divider logic, making the 18.2Hz tick too fast.
Does somebody know whick clock is being read by the BIOS when in the setup? The RTC or the system clock driven by the 18.2Hz interrupt?
Normally the RTC gets read once at boot or by DOS driver, for example from multi i/o card with RTC. (if not, you start with 1-1-1980)

One way to know find out the oscillator to be put question could be to set the clock to a particular time, save the setup, turn off the PC for one hour or so, and look what time is displayed right after turning on again.