X220 unlocked BIOS: which settings are safe, and which ones will brick the laptop?

[axur-delmeria]

I know that the unlocked BIOS is a veritable landmine, and changing the wrong settings will brick it.

I saw settings for CPU thermal management, like C6/C7 settings and other stuff. Are these safe?

Is there a compiled list of safe and "danger do not touch" settings in the X220 unlocked BIOS?

The only unsafe one I know is : SR-IOV for PCI-E, taken from https://www.win-raid.com/t1976f16-Think ... -BIOS.html

[dr_st]

Why would anyone activate SRIOV on X220? It's like buying a water slide for your backyard when you have no pool.

No BIOS setting should brick the computer. If it bricks it, it means the BIOS sucks beyond belief. Yes, we've seen such things with Lenovo official BIOS as well, apparently, but not on X220 as I recall.

[axur-delmeria]

No BIOS setting should brick the computer. If it bricks it, it means the BIOS sucks beyond belief.

Well, this is the unlocked (AKA modified) BIOS we're talking about, which has all the settings shown, even those that may/should not be tampered with.

In any case, I may have found the answer to my own question here: https://thiccpad.blogspot.com/2018/01/x ... urces.html

Excerpt from that page:

Unlocked BIOS adds these features:

Whitelist removal
Unblocked AES-NI
Unblocked advanced menu
Unlocked memory speed
Unblocked AES MSR 0xE2
New vbios Intel 2119
16Gb 1866 + eGPU solved

Advanced BIOS Options
I have changed these options in the BIOS without bricking. Always be careful. Never change the PCIE SR-IOV setting unless you want a brick. Turns out it doesn't - still, be careful.

Boot Configuration
| Quick boot
| High resolution graphics (disable messes up text)
| Diagnotistic splash screen
| Diagnotistic summary screen
| BIOS level USB
| USB legacy
| UEFI boot
| Legacy boot
| Boot in legacy video mode
ACPI configuration
| ALS support (ambient light sensor)
| FACP PM Timer flag value
Processsor Configuration
| Fast strings (^ speeds up mem copy instruction REP MOVSB)
| Enabled XD
| Machine Check
| Processor Power Management
|    |  Turbo Mode Power Limit Lock
  |    |  Long/short power limit (maximum 36/56)
| | Processor long/short power limit (max 36/56)
| | Long power limit time (does nothing?)
| | IA curent limit (default is 776 (97A))
|    |  C-State Auto Demotion (# demotes C1/C3 to C0)
HDD Configuration
  |   PortTopology
  |   ALPM Mode Select
Memory Configuration
| Mem freq (will default SPD max)
| Max TOLUD
| OneN Mode Support (command rate)
| Scrambler support (scrambles RAM preventing cold attack)
System Agent Configuration
| Graphics Configuration
| | Aperture Size
| | DVMT Prealloc (actual VRAM size)
| | DVMT Total Gfx Mem
| | Render Standby (RC6 state)
| | IGD thermal control
| | IGB turbo mode
  |   PEG Port Configuration
  |    |   PCIe ASPM
  |    |   PCIe Active State Power Management
  |    |    |   ASPM L0s
  |    |    |   PCIe ASPM L1 Support
South Bridge Configuration
  |   SB PCI Express Config
  |    |   PCI Express Controller DMI Setting
  |    |   PCI Express Root Port x
  |    |     |   ASPM
  |   SB Azalia config
  |    |   Azalia PME (sound card stops working when enabled)
Thermal Configuration
  |   CPU Thermal Configuration
  |    |   DTS
  |   Platform Thermal Configuration
  |    |   Active Trip Point Hi/Lo Fan (no effect?)

Notes
^ Read the discussion about fast strings here.
# A more detailed explanation of auto-demotion here.

I was researching more on that SR-IOV issue, and somehow ended up on that page.

[dr_st]

Not bad. Looks like the unlocked BIOS also supports per-port L0s/L1 configuration, which is a nice thing to have on these systems, as it can control compatibility issues with certain ExpressCards, without sacrificing battery life by disabling system-wide ASPM.

[31336]

The only list I know of is the one you already found, and that one is not extensive.

There is one setting, Advanced → System Agent → Graphics → IGD → IGD - TV Control, where just opening the available options is enough for the setup to crash (with BIOS version 1.43 at least). It's not a brick though, once you hold the power button to force shutdown and then power on again, everything works normally.

Also not strictly a brick, and I haven't tried it, but messing with the display settings (changing the display to something not connected, or the resolution to an unsupported one) could potentially be problematic. Too adventurous memory timings could render the system unbootable but it seems there is no option for setting these directly, and it would correct itself anyway once a different memory module is installed.

Since it's really easy to access the EEPROM chip on the X220, I'd suggest making a backup of it, and then you're covered should things go south.

[axur-delmeria]

The only list I know of is the one you already found, and that one is not extensive.

There is one setting, Advanced → System Agent → Graphics → IGD → IGD - TV Control, where just opening the available options is enough for the setup to crash (with BIOS version 1.43 at least). It's not a brick though, once you hold the power button to force shutdown and then power on again, everything works normally.

Also not strictly a brick, and I haven't tried it, but messing with the display settings (changing the display to something not connected, or the resolution to an unsupported one) could potentially be problematic. Too adventurous memory timings could render the system unbootable but it seems there is no option for setting these directly, and it would correct itself anyway once a different memory module is installed.

I don't know if the RAM speed setting is stored in CMOS or EEPROM, but if it's the latter, then it's definitely a brick.

I'm mainly interested in CPU power management, esp. TDP and C-state controls. And also how to fine-tune the Turbo Boost so the CPU doesn't fry itself.

Since it's really easy to access the EEPROM chip on the X220, I'd suggest making a backup of it, and then you're covered should things go south.

Still have to hunt down a SOIC clip. I already have an RPI 2.