(UEFI) Dell XPS 15z L511z modded BIOS - and HOWTO

[TimeWalker]

I think it will suffice .. Build attenders got a 32Gb USB3 usb sticks with preloaded Windows To Go, but I guess it was just redundant.
You can read a Q&A on this feature here: http://technet.microsoft.com/en-us/libra...92680.aspx

[TimeWalker]

Yeah guys, it's definitely AHCI mode that is screwed.
Just tried switching my installation to utilize IDE (ATA) by using this nifty program by stevemk14ebr from MDL forums: http://www.datafilehost.com/download-287e196a.html
I had switched the mode to IDE for Windows and then tried to load the capsule from the USB flashdrive and it booted into Windows without a hiccup. So if my bios went toast I could recover. The downside is that windows won't boot in AHCI mode now and I have to set IDE in BIOS.... but! I had a pal of mine show me how he is able to switch the modes in BIOS only and be able to boot in both AHCI and ATA .. might have to ask him if he still recalls how he did that.

Update:
Use the above utility and switch from AHCI to IDE and back. It will alter your registry to enable both boot modes - msahci and pciide. Also windows will be able to boot using the BIOS.cap recovery capsule!

[TimeWalker]

Were you able to test what I had posted above, krzysio30 ?

[TimeWalker]

I'm actually starting to understand why Packard Bell's / Acer's service manuals describe the use of Startup.nsh along with PFlash.efi - to avoid the need of a working operating system or a HDD even. They come with unlocked shell from the factory and after you unplug HDD it will boot into the shell (this is what the Acer guy from Singapore described the tech person did to boot the laptop in crisis).
So what happened was:
- The tech guy had a dvd or a flashdrive with stripped BIOS.cap (truncated 180000h 0x00 padding layer), a startup.snh script which executes PFlash.efi which flashed the xxxx.fd bios image in silent mode.
- The machine is put into recovery mode by Fn+Esc key combinarion
- The PEI modules FatLitePei or CdExpressPei load the recovery capsule BIOS.cap into memory and emulate the bios this way
- The laptop starts and as there's no HDD present it loads up shell (because they have it as a boot option, on our Dells when nothing is found to boot from the Boot Managers pops up, on theirs it will be Shell presumably).
- Shell does 5 seconds countdown before initiating the startup.nsh and after 5 seconds executes the startup script
- Startup script invokes the PFlash.efi which is able to start this time because there is a capsule loaded into memory at this point of time, so using the arguments which were passed to the flasher it flashes the xxxx.fd specified in the script.
- The Shell flasher reboots the system and the on-chip bios gets reflashed without the need for an OS.

Since our Dells come with UEFI boot disabled by default (meaning we can't enable it and save setup - [F10] and reboot because we'd lose the recovery capsule from memory right away).. nor we have an access to the ShellInternal ... it's a good practice to find a way to set UEFI Boot default as Enabled in the advanced setup module. Then it would be possible to put the shell as bootx64.efi onto the same external media device, after machine finishes up loading bios from usb we'd hit F12 and select USB/DVD to initiate shell and start the startup script to flash from EFI Shell flasher..

[HairyCube]

I had switched the mode to IDE for Windows and then tried to load the capsule from the USB flashdrive and it booted into Windows without a hiccup. So if my bios went toast I could recover. The downside is that windows won't boot in AHCI mode now and I have to set IDE in BIOS.... but! I had a pal of mine show me how he is able to switch the modes in BIOS only and be able to boot in both AHCI and ATA .. might have to ask him if he still recalls how he did that.

I think it might work in both modes if you uninstall all IDE/ATAPI controller drivers in the Device Manager and replace them with standard drivers. Or try booting in Safe Mode.

[krzysio30]

Were you able to test what I had posted above, krzysio30 ?

I can both boot modes - msahci and pciide but with on-chip bios.
With USB-based bios i can't save changed setting from AHCI to ATA.

[TimeWalker]

Were you able to test what I had posted above, krzysio30 ?

I can both boot modes - msahci and pciide but with on-chip bios.
With USB-based bios i can't save changed setting from AHCI to ATA.

You don't need to be changing anything in your bios (and that's what I had described before -you basically can't, since its a memory capsule), if the OS is set to boot in both modes then you'd be able to boot into it using the usb-bios loaded into memory. As soon as the fan stops spinning spam F12 to enter Boot menu and select your HDD to boot into windows. This is the part where MBR installation comes useful, because you won't be able to boot UEFI installation if you brick the bios 'cause the option is disabled by default..

Go to regedit > HKEY_LOCAL_MACHINE > SYSTEM > CurrentControlSet > services
Make sure Start key is set as 0 for both msahci and pciide -> this allows to boot on both AHCI and ATA modes without changing bios settings to a corresponding boot mode. Of course this is just a workaround .. most people won't have this enabled in case of an accidental bios brick ..

[krzysio30]

Were you able to test what I had posted above, krzysio30 ?

I can both boot modes - msahci and pciide but with on-chip bios.
With USB-based bios i can't save changed setting from AHCI to ATA.

You don't need to be changing anything in your bios (and that's what I had described before -you basically can't, since its a memory capsule), if the OS is set to boot in both modes then you'd be able to boot into it using the usb-bios loaded into memory. As soon as the fan stops spinning spam F12 to enter Boot menu and select your HDD to boot into windows. This is the part where MBR installation comes useful, because you won't be able to boot UEFI installation if you brick the bios 'cause the option is disabled by default..

Go to regedit > HKEY_LOCAL_MACHINE > SYSTEM > CurrentControlSet > services
Make sure Start key is set as 0 for both msahci and pciide -> this allows to boot on both AHCI and ATA modes without changing bios settings to a corresponding boot mode. Of course this is just a workaround .. most people won't have this enabled in case of an accidental bios brick ..

I enter Boot menu and select HDD but windows don't start I have black screen.
Start key is set as 0 for both msahci and pciide

[TimeWalker]

I enter Boot menu and select HDD but windows don't start I have black screen.
Start key is set as 0 for both msahci and pciide

Then we need input from kasar as in .. if he is actually able to boot into the OS on his L502x.
Mine does the following

[TimeWalker]

HairyCube, can you confirm the same behavior for your Quanta DIS (AMD-based) Vostro 3450 machine ?