Issue reading Macronix BIOS-chip in HP Elitebook

[ValleyDude2605]

Hi, I'm trying to revive an HP Elitebook 840 G2 with a bricked bios. Problem is that I'm stuck on getting a dump from the BIOS-chip, it doesn't seem to give me the correct output.

I'm using a Raspberry Pi 2B+ with Flashrom and a Pomona SOIC8-clip. The chip in question is a Macronix MX25L12873F (datasheet here). Flashrom detects the chip fine - or so it seems, it's detected as a "Macronix MX25L12835F/MX25L12845E/MX25L12865E". Reading takes quite long, I'd say about ten minutes or so. When I open the output in a hex-editor every line is like this:

C2 20 18 C2 20 18 C2 20 18 C2 20 18 C2 20 18 C2

Does anyone have an idea why this is, and what I could change to get a correct dump of the BIOS?

[piernov]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Desolder the chip.

[ValleyDude2605]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Hi piernov, thanks for your reply. It's that simple? Desoldering will make it able to read the chip?

Unfortunately that's not really an option for me right now, I have to do it in situ. And I've seen plenty of posts and videos online where it worked, so I'm just baffled why I keep getting stuck on getting a correct dump.

[jasko_jacker]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Not all programmers are able to work with the soldered chip.
With the chip soldered, it is possible that the power supply or some signals are attenuated by the connection with the motherboard.
As he cannot read it correctly he will certainly not be able to program it. For the dump you can find it in the bios section or you can request it.

[KingBonecrusher]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Try this:

1) disconnect battery & ac
2) connect programmer
3) connect ac (ONLY AC!)
4) read eeprom

[ValleyDude2605]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Thanks for the feedback, but I'm afraid I'll have to give up on this project. I tried nearly everything:

- different programmers (RPi, CH341A Black, CH341A Blue)
- different voltages (no GND+VCC, 3V3, 5V)
- Elitebook not powered on, Elitebook connected to AC but not powered on, Elitebook powered on

Guess I'm out of options here.

[RethoricalCheese]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Raspberry can always read soic8 HP bios without desoldering but it takes a certain action first. In your case, you are not able to do that because your machine does not post. Thus you need to desolder.

Btw, use the command

flashrom -p linux_spi:dev=/dev/spidev0.0[B],spispeed=10000[/B]

10000 is quite fast and reliable. 20000+ might have issues with some chips.
Default is only 1000 if I am correct.

[ValleyDude2605]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Thanks @RethorialCheese, I will give it another try then.

Perhaps this is a dumb question, but you say that I can't read the chip because the machine does not post. But if I desolder, then there is no post either, right? Or is that the difference between reading/flashing in situ and doing it with a desoldered chip?

[Bonzas]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

AFAIK your chip is 1,8v, you need 1,8v converter.
you may be able to read and backup file from these chip but u'll got error when verifying file after flash. so far, i always failed when reprogram bios without desoldering chip from motherboard

[ValleyDude2605]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

According to the datasheet this is a 3,3V chip.

[RethoricalCheese]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

HP EliteBook, Probook and Zbook always use 3.3V chips.

If the machine posts and you turn it off but leave charger connected, it will be in a state where you have no problems reading with raspberry. If you desolder, there aren't any other parts disturbing. So either post and shut down to read on board or just desolder.

[Bonzas]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

Ah my fall, sorry i didn't see your attachment. There 25U have 1,8v not 25L

[ValleyDude2605]

Re: Issue reading Macronix BIOS-chip in HP Elitebook

HP EliteBook, Probook and Zbook always use 3.3V chips.

If the machine posts and you turn it off but leave charger connected, it will be in a state where you have no problems reading with raspberry. If you desolder, there aren't any other parts disturbing. So either post and shut down to read on board or just desolder.

This actually seemed to do the trick! I booted, shut down and then tried to read the chip with success. I did four reads, just to be sure, and they all checked out to be exactly the same. Removed the BIOS-password and reflashed the BIOS, all good to go now.

Next project: fixing the "ME state in recovery mode" error.