How to save a soldered BIOS?

[HardwareGeek]

I like to play and modify hardwares. Recently i bought a faulty board, thinking i could fix it with some luck, to make some modifications and test some hardware on that. You know the starter of so-called revolutionary and life saving GA-BX2000 series dual-bios boards...

The board is a GA-BX2000+, and somehow the guy who once used the board succeeded to make both BIOSes out of order. The bad news both BIOSes are soldered to the board. And the boot-block is also out of order. So i can't prepare a "blind-flash" disk in my main system
All the signs indicates it's a BIOS problem, however i don't know how i can fix such a problem without such a tool that would let me to write on EPROM while it is still attached to board.

The screen is completely blank, board's receiving power, fans, harddrives and all the slots too but the floppy shows no sign of life. So it made me think boot-block was dead too.

I can think of an other alternative solution which i am not sure about if it would help or not. Maybe finding a good homogeneous BIOS from somewhere and touching its legs to bad BIOS and starting the PC in that position can work. But i'm not sure.

I'm open to suggestions of all wise and experienced users on this subject.

Thanks beforehand to all contributers

[cp]

unsolder the main bios and flash it elsewhere. if you can't unsolder it you can try to program another eeprom on another board and solder it on the main bios chip (piggyback style :)). just make sure that the main bios (the damaged one) is disabled. there's a pin on the chip that's called 'chip enable'. connect it to a switch, one side to the main bios, the other to the piggybacked bios. to boot select the piggybacked bios, load uniflash, switch over to the main bios, redetect the chip and flash the bios in the (now active) main chip. that's it :)

[HardwareGeek]

Thanks for your reply cp, but i don't have any idea about which is the "chip enable pin" on this BIOS chip. I'll try my best and search for it. I'll also consider about gaining some soldering skills. By the way, wouldn't i harm the chip(or the data stored in) while soldering or desoldering it?

And i've read sth about "forcing a BIOS error" Any chances to boot and save system in such a fashion?

[cp]

can you please post what's written on the bios chip (please remove any sticker first!).

when the bios is overwritten (especially the bootblock) there's nothing you can do to make the board work. without a working bios it's simply dumb as a pile of silicon, metal and plastic can be.

[HardwareGeek]

It follows as :
SST
39SF020
90-4C-NH
001416-B

Is there any chances that the second BIOS is ok, but simply doesn't kick in due to bad configuration?

[edwin]

Before making any repairs on this one, check the state of the capacitors. This one is prone to the http://www.badcaps.net syndrome as well.

[HardwareGeek]

I checked all the capacitors before, they all seemed to be ok in appearance. But thanks much for the link, it may become handy in the future.

[cp]

SST 39SF020 datasheet

okay, the pins that you're looking for are: CE# and OE#
they are (assuming there is a plcc device on the mainboard) on pin 22 (CE#) and 24 (OE#). with those pins you can control the shutdown of the device and the tri-stating of the data pins. if you want to make an emergency bios just do the following: get another SST 39SF020 (any +5V 2MBit plcc flash would do, but we'll keep it simple and secure) and program it with your fav. bios in a working machine. see the FAQ about hot-flashing or use an external programmer. once you're done bend up pins 22 and 24 on the new chip. additionally bend up pins 22 and 24 on the normal bios chip, too. now solder the new bios chip on the normal bios chip making 1:1 connections (except 22 and 24). watch out for correct orientation! there is a notch!
now take a 2x3 terminal switch and solder the center terminals to the mainboard. one center pin goes to the pad where pin 22 was soldered to and the other goes to the pad where pin 24 was soldered to. now connect the upper terminal to pin 22 and pin 24 on the normal bios chip and the lower to pin 22 and pin 24 on the new bios chip.

this is what it should look like (just connect pin 24 to the second row of 3 terminals)

Code: Select all

		            __
	        	   _\ \_
        		  |_____|
 		          | | |    ___
           	   | | |   /   |
     ____        | | |  | NEW| PIN22
    /    |       | | |  |____|-+
   | ORG | PIN22 | | |         |
   |_____|-------+ | +---------+
                   |
                   |<- TO MAINBOARD PAD22

[HardwareGeek]

Thank you very much cp. You are indeed a Master Flasher. I've bought some related material, now looking for a suitable EPROM chip. I'm also thinking to buy a Willem Eprom programmer. Would you suggest it?

And also i'm thinking about other option due to i may not be able to find a suitable chip : desoldering the chip, flash it with an eprom writer than solder it back. But i've read about this may result with data loss. What do you say about that?

Thanks one more time for sharing your great knowledge.

[cp]

an external programmer is always a nice thing to have. but if you're just looking for a (cheap) solution to program mainboard bios chips i would rather recommend the ct'flasher(supported by UniFlash) or the IDE Flasher. i personally own the ct'Flasher and it's a nice handy thing in combination with uniflash. the parts count on the ct'Flasher can be reduced even further as the I/O and memory range jumpers are not needed for normal operation. simple shorts would do :)
if you're skilled enough to build some simple hardware and you're running linux you should check : http://ctflasher.sourceforge.net/

for the bios chip any 2MBit bios chip will do. just make sure it needs +5V programming voltage (a datasheet will help). some intel chips need +12V programming voltage (and sometimes even +12V Vcc).

i'd prefer desoldering, programming and resoldering to the method with the switch i suggested. but that's just because i do have smd soldering equipment and i took a three year apprenticeship where i worked with smd parts on a daily basis (there were some almost impossible boards to be assembled ;)). if you don't own at least something like this you shouldn't try to remove the bios chip. you'll most probably end up with a destroyed motherboard. back to the question: i've never seen a flash chip with data loss due to soldering. before they loose data they most probably start loosing their pins if someone less skilled is messing with that chip ;)

i just have another idea how to flash plcc chips that are soldered to the mainboard. it requires an external flasher and a homebrew adapter. one side is plugged into the flasher with a socket. on the other side just solder a plcc socket to the cable and plug it on the plcc bios chip sitting on the mainboard. just make sure to double check the cabling before trying to flash anything ;) maybe i can post some pictures that make it easier to understand what i'm up to.

[HardwareGeek]

I have never tried desoldering relatively micro sized chips before. I have experience in soldering with just fixing simple circuit failures. Probably i would either ruin the board or the chip while desoldering. I really need more electric and electronic knowledge, pure softwate skills already proved to be insufficient for my needs.

I should have studied computer and electronic related profession instead of economy i guess. It's difficult and slow to learn on your own. I should keep reading and practising more on theoretical and practical hardware matters.

I'll keep reading your posts on the forum. There is much i can learn from you.

[cp]

okay, i will try to put up a howto on flashing soldered smd plcc chips this weekend.