r/techsupport • u/Certified_GSD • 8d ago

Open | Hardware EEPROM Flashing - Hash Mismatch

I’m trying to dump and flash a BIOS chip for an HP Elitebook 640 G9. I’ve got a CH341 USB programmer and the pogo pin reader for a WSON8 chip.

I’m not sure if I’m doing something wrong because every time I try to dump the BIOS with NeoProgrammer, I do a second dump. There is a hash mismatch between the two so something is being lost. Holding it still for four minutes can be tricky but I’m pretty sure all eight pins are making good contact the entire time. I’m also making sure that Pin 1 on the pogo contacts is correct.

The IC is correctly detected, I just can’t get it to dump twice with the same hash. Is there something I’m doing wrong with flashing this chip or a setting I need to enable? It was suggested to fill the buffer but that did not make any difference. I’d appreciate any advice. I also want to avoid desoldering and removing the chip as that is beyond my expertise and tools.

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u/donaciano2000 7d ago

Can you diff them and see if the change is small and in the same location or random? If it's a bad connection they'll all be in totally different spots.

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u/Certified_GSD 6d ago

It must be a bad connection then, because when I compare the files it’s always different parts that are different. Some sections are the same and some are completely different. The hashes are wildly different too.

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u/donaciano2000 6d ago

Sweet. So we have confirmed our suspicions that it's a bad read. We still don't know if it's a spotty connection or a board interference. Hashes are always wildly different btw. They're designed to change drastically with a single bit differing from the input. Even if you could break the binaries into chunks and reassemble what must logically be the true data, I would not recommend that because the write failing is a much bigger problem than a read failing. You're right to be persistent on getting identical reads.

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u/Certified_GSD 6d ago

At this point, I’m not sure what the best option is. I might be able to trade it, but I do like the keyboard and small form factor and it does have a more modern CPU. If I were to sell it to someone who doesn’t care about running Windows, I wouldn’t be able to replace it with something as good or new.

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u/donaciano2000 6d ago

https://www.digitalandrew.io/chip-off-firmware-extraction-and-modification/ You can get clips for those pins, and there's also a SOIC8 cable that'll attach to your CH341 (make sure you don't have the bugged version with 5v even when it's set to 3.3v). But it might need to come off the board.

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u/Certified_GSD 6d ago

I’m pretty sure these contacts are too small to clip to. Someone suggested keeping it plugged in when trying to read the chip, sounds like that might avoid backfeeding like the article you linked talked about.

I don’t have a multimeter. How would I check to make sure my CH341 is feeding 3.3 volts? I’m assuming it is because if it fed the chip 5v I’m pretty sure the chip would be fried. But it still works fine.

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u/donaciano2000 6d ago

https://oldrigrevive.com/guides/ch341a-voltage-fix/ Don't skip on a voltmeter. You might be able to tell which one you have without it. But you need to know if a chip is 5v or 3.3v or (oh my!) 1.8v before you connect to it. You can use the chip model numbers to find the data sheet and check the voltage there.

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u/RCEdude101 7d ago

A few things worth trying:

  • Read the chip with the laptop plugged in, then with the charger unplugged and the battery removed.
  • Test different software versions, such as AsProgrammer, NeoProgrammer, and CH341A Programmer. Try selecting a similar chip model or another chip with the same capacity.
  • Experiment with the 3.3V mod.
  • Check whether the chip is 1.8V. If it is, use a compatible 1.8V adapter.

I know you want to avoid desoldering, but if you have a soldering iron, practice on some junk boards first. That's how I approached my first laptop BIOS chip successfully.

Some alternatives

AsProgrammer_2.1.2
CH341A Mini Programmer (Black Edition) By_NSC
CH341A programm v1.13
CH341A Programm v1.18
CH341A programm v1.29
CH341A programm v1.30
CH341A programm v1.31(1.4) (CH341AFree)
CH341A programm v1.34
CH341A programm v1.38
CH341A programm v1.40
CH341A programm v1.45
CH341A Tools
CH341A_CH347 Programmer V2.21
Colibri_CH341
NeoProgrammer v2.2.0.3
NeoProgrammer v2.2.0.10-Upgrade
AsProgrammer_1.4.0

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u/Certified_GSD 6d ago

I was under the impression that having it powered on/plugged in would damage the chip. Is this safe to do while reading/writing?

I’ve tried two different versions of NeoProgrammer and one version of a different software that I can’t remember the name. None were successful. I can’t sanity check because I don’t have a known good config or known good hardware either.

The chip is 3.3v. The data spec sheet says it is so I’m assuming that’s fine. Now, the markings on it are different than what’s detected in NeoProgrammer, as in NP detects that it’s specifically just a generic 256Mb memory chip. But if I enter in the markings in the search function, nothing comes up.

Maybe I need modern software? Apparently NP is a few years old and maybe doesn’t have the latest chips?