Write-protection jumper on Acer CB514-3H-R0D5

[MD7070B]

I have an Acer CB514-3H-R0D5 Chromebook, which corresponds to the board name of Markarth. I notice it is listed as supported on this page, however I am running into a few challenges due to the write protection, which I am struggling to disable. The ultimate goal is to replace ChromeOS with Linux.

I have found pictures of other very similar Acer 514's which have a fairly obvious jumper on the motherboard, which I believe disables the WP. However, I have taken the back off of this model, and cannot see any obvious jumpers. Can anyone please provide some guidance on which is the correct jumper to use to disable WP on this model?

[MrChromebox]

it's the same jumper as on Frostflow, just might not be in the exact same place. I don't have a picture else it would be on the site. A different model CB514 is not going to be relevant at all.

[MD7070B]

Thanks for the confirmation. I will take a look at the board tomorrow and see if I can locate it.

Perhaps I will post a picture of my specific mobo just to 100% confirm.

[MrChromebox]

if you can, I can add it to my site. it will be the same J35 jumper as frostflow

[MD7070B]

Thanks. This is my motherboard on the CB514-3H-R0D5:

J35 circled in the 2nd image. I will attempt to solder it and hopefully problem solved.

I reckon it may prevent future confusion if you were to update the site :-), for any others very new to the specifics of Chromebooks.

[MD7070B]

And I assume I am correct in thinking that the Write Protection needs only be disabled whilst the bootloader is replaced? Or must it remain off?

[MD7070B]

Just tried the jumper, still having issues. Read this page https://docs.mrchromebox.tech/docs/firmware/wp/disabling.html#disable-ap-ro-firmware-verification, and when running gsctool -a -I I get a line at the bottom of the output AllowUnverifiedRo - Never - does this mean I have to use CCD with this device?

[MrChromebox]

Just tried the jumper, still having issues.

how did you connect the two?

Read this page https://docs.mrchromebox.tech/docs/firmware/wp/disabling.html#disable-ap-ro-firmware-verification, and when running gsctool -a -I I get a line at the bottom of the output AllowUnverifiedRo - Never - does this mean I have to use CCD with this device?

yes. It means you have to unlock the CCD and set the flag to 'Always'. It does not mean you need to use a SuzyQ cable.
Note that failing to set the flag does not affect WP - it affects your ability to boot after flashing non-Google signed firmware.

[MD7070B]

Thank you. I tried to solder the jumper. Its not the neatest job but I believe it is connected. Is there a command I can run to verify this?

yes. It means you have to unlock the CCD and set the flag to 'Always'. It does not mean you need to use a SuzyQ cable.
Note that failing to set the flag does not affect WP - it affects your ability to boot after flashing non-Google signed firmware.

OK. I was hoping to avoid using the SuzyQ, as I don't have one available right now. I will try and figure out how to unlock the CCD and set flag to 'Always'. Hopefully this will fix my issue?

[MrChromebox]

OK. I was hoping to avoid using the SuzyQ, as I don't have one available right now. I will try and figure out how to unlock the CCD and set flag to 'Always'. Hopefully this will fix my issue?

the AllowUnverifiedRO flag is completely separate from WP. You do not need a SuzyQ for it.

you need to either bridge the jumper or use a SuzyQ to disable WP on MARKARTH. the sudo crosssytem wpsw_cur command should tell you the hardware WP state. I've not done it but others have on Frostflow, and they're both derived from the same baseboard

[MD7070B]

Thanks again.

I think the command mentioned above specifically is crossystem wpsw_cur (typo). For anyone reading this in future. Anyway, it returned 1. So maybe my bridging of the jumper was not successful. I will check. I also have the battery disconnected at the moment.

[MD7070B]

Reconnected battery, and followed the steps here:
https://docs.mrchromebox.tech/docs/firmware/wp/disabling.html#step-2-disabling-write-protection, but crossystem wpsw_cur still returns 1, and gsctool -a -I returns:

State: Opened
Password: None
Flags: 000000

And then all the flags. Most are either Y Always or Y IfOpened.

I did notice that when doing the Enabling CCD step, I never got a PP prompt. The device simply rebooted out of Dev mode into secure mode.

Not sure what I am doing wrong...

[MrChromebox]

So maybe my bridging of the jumper was not successful.

it would appear not

Not sure what I am doing wrong...

run the commands as per https://docs.mrchromebox.tech/docs/firmware/wp/disabling.html#disable-ap-ro-firmware-verification

report any errors.

[MD7070B]

Ran the commands here: https://docs.mrchromebox.tech/docs/firmware/wp/disabling.html#disable-ap-ro-firmware-verification.

Note: I expect crossystem wpse_cur was still still showing 1 before starting this (forgot to check), but considering this clause in above link If you want to flash custom firmware, you must use the CCD method above to disable firmware write protection, regardless if the device supports disablement via battery disconnect or a jumper as well., I thought perhaps the jumper is irrelevant when using this method. Or do we need to bridge the jumper and use CCD?

Anyhow, the process went as follows:

• Boot into dev mode, select Boot from Internal Disk.
• Open VT2 terminal.
• Login as root.
• Ran gsctool -a -I. I omitted the grep part, as I couln't type | on the Chromebook keyboard! The output was

State: Locked
Password: None
Flags: 000000
Capabilities, current and default:

**Many Attributes, ending with:**
AllowUnverifiedRo - Never 

So I took that to mean the device does have a Ti50, as per the docs.

• Then next thing I did was to try and unlock the GSC by running gsctool -a -o. When I did this, the Chromebook rebooted into normal mode. I rebooted back into developer mode, and ran gsctool -a -I AllowUnverifiedRo:always. This gave me a load of Press PP button now! prompts, and finally a PP Done! message.

• Running gsctool -a -I now gives AllowUnverifiedRo Y Always (Never).

• The crossystem wpse_cur command doesn't seem to work anymore.

I guess this means the process was a success?

[MD7070B]

I just tried to run the firmware script as per here https://docs.mrchromebox.tech/docs/fwscript.html, but received the Warning: Failed to open the file firmware-util.sh: Read-only file system.

Still missed a step then.

[MrChromebox]

Or do we need to bridge the jumper and use CCD?

you need to:

• disable HW WP (jumper or CCD)
• disable AP RO verification (gsctool or CCD)

as I couln't type | on the Chromebook keyboard!

non-USA keyboard layout? it exists on all the US/UK keyboards I've seen

The crossystem wpse_cur command doesn't seem to work anymore.

sudo crossystem wpsw_cur is the command to check HW WP.

Warning: Failed to open the file firmware-util.sh: Read-only file system.

the instructions specifically say you cannot log in as root and run the script, you need to log in as chronos.

But, HW WP needs to be disabled first. It's possible the jumper doesn't work on Markarth for whatever reason, and that CCD/SuzyQ is the only way to do it.