How to make SeaBIOS the default on your Acer C720

Divulged this evening by Duncan Laurie on the coreboot mailing list:

If you want to boot SeaBIOS by default and you have unlocked the SPI flash write protection you can set flags in the (write protected) “GBB” flash region that will make it boot legacy mode by default.

In Chrome OS there is a script called set_gbb_flags.sh that will do this for you. Run the script with no arguments to get a list of possible flags and then to enable short dev mode screen (1 second timeout) followed by default legacy mode boot you could use these flags:

GBB_FLAG_DEV_SCREEN_SHORT_DELAY 0×00000001
GBB_FLAG_FORCE_DEV_SWITCH_ON 0×00000008
GBB_FLAG_FORCE_DEV_BOOT_LEGACY 0×00000080
GBB_FLAG_DEFAULT_DEV_BOOT_LEGACY 0×00000400

set_gbb_flags.sh 0×489

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40 thoughts on “How to make SeaBIOS the default on your Acer C720”

  1. There has been the occasional report of the RW Legacy (i.e. SeaBIOS) slot being wiped out and unusable. I suspect this is because the person(s) perhaps didn’t disable write-protect, or perhaps some other issue. Just be aware it *isn’t* fool proof.

  2. Thank you for this post.

    I’m just curious what would happen if you pressed the space bar after performing these steps. Would it wipe out these settings? Could it potentially brick the machine?

  3. How i unlock the SPI flash write protection ?

    I just try to run the set_gbb_flags.sh 0×489 and it apears:

    /usr/bin/old_bubs/set_gbb_flags.sh: 81: flashrom: not found

    Dont know what to do, help pls !

  4. ( im using c720 on chrome os with developer mode ) And what i want to do, is not to push Control + D everytime i open my chromebook. Then i need to that ? and if i need to do it… ( like i was trying )

    How i unlock the SPI flash write protection ?

    I just try to run the set_gbb_flags.sh 0×489 and it apears:

    /usr/bin/old_bubs/set_gbb_flags.sh: 81: flashrom: not found

    Dont know what to do, help pls !

  5. If you *just* want to get rid of the delay, as opposed to enabling the SeaBIOS slot by default, you will need to adjust the number you type there. Run the script without any arguments to get info on what each number means.

  6. Is there a way to make SeaBios the default with in the linux side of things? I got a little hasty and compleatly removed my chrome os partiotion to make room for Xubuntu and any storage I could get out of the 16 GB SSD. Am I just going to have to re-install chrome os, removing Xubuntu in the process, and making Seabios the default from there? Also, if I do that and then remove chrome os again will it revert back to staying on the splash screen and defaulting to chrome os?

  7. I think that script is in the CrOS SDK (albeit named with “old” at the front) so try installing the CrOS SDK (mini-layout) running it from there in your Xubuntu install.

    It’s technically easier just to go back to ChromeOS, if you haven’t anything in your Xubuntu install that needs saving/preserving. And no, it won’t change the flags back unless you expressly do so with the script. For extra safety, once the flags are changed as above, the Chromebook won’t do anything if someone presses “space” by accident except beep. HTH.

  8. Can someone please upload the c720 factory bios, I no longer have mine and would love to go back to factory for now. I have googled all I can but can’t seem to find the image. Thanks in advance.

  9. I was getting really tired of my 2-year-old constantly button-mashing and wiping out my Ubuntu install. I removed the screw and ran the script as root with the flags you recommended (0×489) and everything works like a charm! Thank you so much!

  10. Hey there, thank you for the guide, it worked perfectly. I am looking to reset those flags to the default- do you know how I could do that?

  11. I want to not have to press Ctrl – D on boot up to pass Scary Boot Screen. So only the 0×000001 Flag I want, I have a HP Chromebook 14 Snow White and do not care about Seabios at all – I don’t use it.

    Given this do I need to remove write – protect screw, if so where is it? I can’t seem to find any documentation online in regards to the screws position on HP Chromebook 14?

    Does the chromebook still beep each time it boots up with shortened Boot Screen?

    Regards – Harrison

  12. Yes, changing the GBB flags requires removing the write-protect screw, because the ROM has to be read and rewritten during the process.

    There is a picture of where the screw is somewhere, but I’m not sure I’d be able to find it easily. It is situated on the right-lower side of the board, and there is a gap in the surround (which the screw makes a circuit of when in). Can’t remember whether it’s on the top or bottom side, so you make have to take the board fully out to get at it.

    I don’t know whether it still beeps with just that one flag, you will just have to try it.

  13. Mr. Lewis

    Thank you for the work and publishing you’ve done regarding these BIOS.

    I would utilize your Bios for the ‘falco’ but I am ‘concerned’ about the operational integrity of the chromebook when you state the power saving function is even worse than normal? Do I misunderstand? Would you say the Bios you have for the HP Chromebook 14 falco is satisfactory for use or useful with notable limitations?
    If it still needs work, do you intend to work out the kinks, if so , any idea when?

    Again thank you for the work you’ve done and the dissemination of that information.

    BN

  14. I take it you’re using the guffy language because English is not your first?

    You are probably better off just changing the GBB flags. The power saving problem is caused by the TPM module. There are a couple of patches which do away with the TPM code completely, when not using ChromeOS. However, they are of limited use, because the Linux kernel XHCI driver won’t currently allow the laptop to go in and out of suspend more than once, anyway. So, no, I don’t plan on doing any more with it until the kernel XHCI driver is sorted out.

  15. Guys!
    I erased BEOS, is there any way to bring my Aser c7200 back to live ?
    Now I have SeaBIOS, but its not working :)

  16. Dear all is ok only driver not workin.

    We waitin for another tutorial how to change in default factory google os. Windows work well but this model is disign for google os. any news pls let me know how to factory reset in G.OS

  17. The laptop is Acer C720. I have installed windows 7 is work well, but problem is for some driver.

    Now need to change in chrome os.
    What can i do?

    You asked to create chrome os usb and to change flags back to 0.
    How to change flags back in 0?
    In my machine i have windows 7 for moment :/

  18. Hi John

    Thanks for this steep.
    I have created USB and work very good but in sudo -s need password?
    What can i do?
    And the moment i have run set_gbb_flags.sh 0×489
    flashrom: not found

  19. It seems to be locking people out at times lately. It should be open to everyone. Anyway, after the last time it happened I decided I couldn’t trust it any more. That’s why you can download the static Flashrom from my site, and I’ve also done my own write-up on my own procedure (using kpartx is a whole lot easier than supplying losetup with the right sector, especially if it changes).

    https://johnlewis.ie/extracting-the-shell-ball-rom-using-a-chromeos-image/

  20. John Lewis: Thanks!

    I ended using your tuto! Working like a charm.

    Btw, I was using your last c720 build, but with the new kernel 1.17Rc1 or Rc2 my xbacklight is broken. Do you have any idea about that?

  21. Yes. I am looking at the at the moment. It’s because of a change in the kernel and the way it deals with back-lights since 3.15. Currently, the kernel identifies whether to enable the back-light using the subsystem vendor ID’s written into the firmware. I have not been changing this value since I didn’t know what it was for, and it didn’t seem to do very much. However, to do things properly the video BIOS should report it has a backlight so that the kernel picks it up. So, I am looking at a way of getting such a BIOS, and including it in all the Haswell builds so that the back-light works, but the need for worrying about subsystem ID’s is obviated. Expect an update in the next day or so.

    Here’s more info. Scott is the one who enlightened me about the issue.

    https://www.libreoffice.org/bugzilla/show_bug.cgi?id=79813

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