Posted: Wed Oct 07, 2009 6:07 Post subject: Using the JTAG connector on a PC motherboard?
Hey all, i need some help on this one. I have an Asus M2N-E SLI board from a friend, which booted, but displayed no video on either PCI-E slot. I have gotten it to work with an old PCI video card, and thought i'd use it as a server. Its BIOS was very old and buggy, so i updated it (using a floppy). Big mistake... The update was successful but now the board is REALLY dead. My guess would be that the new BIOS has some extra code which detects that the chipset is faulty (since both PCI-E slots are gone) and doesn't let it power on.
I only have a big old soldering gun, no way i could unsolder the BIOS chip with that. However i found that the mobo has a JTAG connector (7 pins). Could i possibly use that to reflash the old BIOS into it? Any help is welcome.
Clearing CMOS was the first thing i tried. Anyway this has become low priority, i kinda forgot about the board as i have another one.
The guys over at Wim's did help me with an Asus board a few years ago, but i don't know how much they could help on this one. I'll eventually drop by this guy with the programmer, have the chip reflashed, and it'll work.
Some BIOS have the ability to boot from a floppy for re-flashing the bios. This used to be pretty common.
You make a DOS boot floppy with the bios flashing program and the original or correct BIOS image, and you set up the autoexec.bat file so that when the floppy boots, it will automatically and silently re-flash the bios, without any user input (using whatever commandline arguments the flashing program needs to bypass the confirmation questions, etc).
It needs to be automatic because you won't have any video during the process. You might have keyboard, maybe not.
I have recovered several motherboards this way. You could try hooking up a floppy to the motherboard and put a disk in and turn it on, and see if it starts reading the floppy like it's trying to boot.
Umm, yes i do have a multimeter, but i didn't get your idea. To check if WHAT detects a flash chip?
You mean checking if the JTAG is connected to the flash chip? Yeah that would have been an idea. I do not have the board anymore (i gave it back to my friend, it used to sit idle on my shelf now it does the same on his shelf ), but i'll check that next time i drop by him.