This only works for certain motherboards that have support for flashing the BIOS from USB without a even a cpu or memory populated.
I'm not sure, but think that functionality requires at least some part of the previous BIOS to be intact.
If this solution doesn't exist/work, you will need to go the route of finding the (often undocumented, sometimes unpopulated) SPI flashing header, and using an external device to directly write a working BIOS onto the SPI flash chip.
Long ago, I botched a mobo BIOS update (Abit BH6), and for the reasons you mentioned/my incompetence, couldn't do another write through the floppy method.
Sold it on eBay (disclosed as such).
Later sent a message to the buyer asking if/how they fixed it. They shared that they did: with a similar mobo, booted the good one up, hot-swapped the EEPROMs and then ran the BIOS update on the bad chip.
I managed to do that once after flashing the BIOS for the wrong board, back when the EEPROMs were in DIP sockets.
Another time I was less lucky and broke an edge off the CPU die while installing the heat sink. This was during the time when the CPUs had exposed silicon with no metal lid. Instant dead CPU, expensive mistake for a college kid.
> you will need to go the route of finding the (often undocumented, sometimes unpopulated) SPI flashing header, and using an external device to directly write a working BIOS onto the SPI flash chip
Y'all these days are spoiled with your headers, test clips, howto videos and cheap EPROM programmers.
Had to reflash an i2c 24-series eeprom on a satellite receiver. You don't want to power the whole board, so gotta lift the VCC pin off the SOIC chip (not hard if you warm it up and pick at it with a soldering iron), solder kynar to leads/nearby lines for VCC, data and clk lines, and aligator clip for GND. Connected to some self-made janky 24 series parallel port interface.
Flashback functionality without a functional CPU generally is accomplished using a separate microcontroller on the board which runs its own code separate from the BIOS. It shouldn't need any of the original BIOS code in-tact, since there's nothing to execute it anyway if there's no CPU installed. :)
It would be smart to implement it as seperate chip, so it can work even with an empty SPI flash. Would also explain why it's only available on some motherboards.
But it wouldn't entirely surprise me if they managed to implement it as pure software inside an extra microcontroller core inside the chipset (or another chip). There are dozens of microcontrollers cores spread out over the various chips on the motherboard which might be abused for such purposes.
Yes, it needs an intact bootblock to do this. I'm actually slightly surprised that BIOSes now have USB support, or at least just mass storage and FAT, in the bootblock. The floppy controller is much easier to program directly to do this.
I think the article in question actually is for older BIOSes that don't have flashback or similar.
Instead this relies on the "BIOS Boot Block" still being intact in the flash, so you do need a partially working BIOS flash, CPU and memory for this method.
I'm not sure, but think that functionality requires at least some part of the previous BIOS to be intact.
If this solution doesn't exist/work, you will need to go the route of finding the (often undocumented, sometimes unpopulated) SPI flashing header, and using an external device to directly write a working BIOS onto the SPI flash chip.