updating BIOS wen no display

two days back i saw my desktop went bad and gave no display. itried everything from changing the RAM to changing powersupply,etcbut nothin worked.yesterday i gave it to a hardware engineer. he fixed it today and he told that the fault was of a corrupt bios. i just want to know how he updated the bios without having any display.

 

He probably took the battery out, round silver thing, and then moved the jumper over for 10 secs., replaced the jumper back and then the battery. This resets the BIOS to factory conditions, nothing to do with updating BIOS.

 

Well, one or the other. Taking the battery out removes the voltage from the CMOS memory semiconductor module and a key characteristic of CMOS memory semiconductors is they must have voltage applied to maintain their stored data. When the voltage is removed, the data is dumped almost instantly (in just a few milliseconds). So removing the voltage causes the CMOS to dump its stored data which resets the BIOS. And moving the jumper shorts that "holding" voltage applied to the CMOS module to ground which is the same thing as removing the voltage. Understand it is because of that special key characteristic of CMOS (Complementary Metal Oxide Semiconductor) modules that motherboard designers decided on using CMOS modules. CMOS devices have been around much longer than PC motherboards. If the electrical engineers designing the motherboards wanted something that would hold on more aggressively to the user's custom BIOS settings (which is what the CMOS memory module is used for), they would have selected another type memory modules besides CMOS - perhaps some sort of EEPROM, similar to the BIOS chip itself. Some designers also use storage capacitors to help hold the voltage on the CMOS pins when the battery is removed. But these bleed off quickly and within 15 - 30 seconds (at most) the voltage has degraded enough for the CMOS to dump its data. But note shorting the pins by moving the jumper instantly discharges the capacitors, as well as causes the CMOS module to dump its data.

I agree with augiedoggie that he probably reset the BIOS. But I do wonder if that is really what he did. It is very rare for a BIOS to truly be corrupted and that would normally indicate a bad BIOS chip, not a bad CMOS setting. And a bad BIOS chip typically needs to be replaced. We used to do that in the old days when motherboards cost several hundred dollars, but today, you just replace the whole motherboard. That said, for simplicity sake, that may be what he said. Perhaps he "flashed" the BIOS. Did he charge you for a new battery? They are only a couple dollars so he may not have separated that out on the bill. Was this a shop you took it too, or a friend?

I wonder too about how reseting the BIOS would restore video unless he removed a card and reverted back to on-board. Or installed a card and switched to it. Because even if the CMOS data was corrupt or lost due to a bad battery, there should have been a basic graphics display.

At any rate, if it works and you are happy, then chalk it up to FM - in my old radio maintenance days, that's what referred to as a certain type of magic. Some might say gremlins.

 

I know we're meant to be geeky in this forum, but you should just ask him! If he won't tell you, then he probably lied or over simplified what he did. If he does tell you, then either have him explain it in English, or post what he says here and we'll translate it.

 

Thanks for the explanation Digerati, I must have been too tired to realize that.:-o 94dgrif is right.

 

No problem. But don't feel bad - CMOS technologies are very commonly misunderstood by those who are not formally trained in electronics. I have even seen where folks recommend leaving the battery out over night! But again, if the designers wanted it to be that hard to reset BIOS settings back to the factory defaults, they would use some other memory device besides a CMOS module.

I note now that many advanced motherboard models have a reset button on back I/O panel so you don't even have to open up the case and risk ESD damage. That is a feature that has been a long time coming and I hope it soon is implemented across the whole price line.

 

Ya, my X58 3X-SLI eVGA mobo has one both on the back panel and one on the board if you're benching it along with power and reset buttons right next to the BIOS. It's an OC'rs dream come true not having to do the reset shuffle everytime!:major

 

As a technician with nearly 60 year-old eyes and not-so-nimble fingers anymore, a CMOS reset button is a dream come true for us too!

 

They need to rename the button though. I've had two people think that that was the button I wanted them to use to "reset the computer". I would have labelled it the 'Clear BIOS' or something like that so the average user knows not to mess with it.

 

Yeah, there are a bunch of terms that really don't make sense but someone used them in the early days so now they are stuck. Actually, I think it is too bad that "Reset" was ever used for the front panel button - I would rather it be "Restart" or "Reboot".

To me, the reset CMOS button should be labeled "Clear CMOS" or if they must use the word reset, label it "Reset CMOS" because that it what it really does. The BIOS data itself is stored in the EEPROM BIOS chip which must be "flashed". You don't clear the BIOS as EEPROMs are semi-permanent (non-volatile) memory chips - they don't forget everything if the voltage is removed. When the voltage is removed from a CMOS chip, all data is cleared from it because they are volatile memory modules, just like RAM modules.

 

Reminds me of EPROMS back in the day when one needed UV light to erase them, not something one could do at home as they had to be re-programmed at the factory. These chips were socketed so no fussing around with switching boards.

 

I've used them too, but they did not have to be re-programmed at the factory. You could buy a programmer - we had several "eprom pocket programmers" in our labs.