• Dell Latitude 5591 ¹⁾
• 2024/06/01: BIOS 1.32

• CSME System Tools v12 r38
• https://github.com/BoringBoredom/UEFI-Editor/blob/master/README.md#how-to-change-hidden-settings-without-flashing-a-modded-bios

FPTW64.exe -d BIOS-dump.bin -BIOS

• Enable/Disable Audio DSP

• Audio DSP is unusable on Linux with SOF with Intel MEI disabled

• Default: Disabled 0
• Ideal: Enabled 1

setup_var_cv Setup 0xF48 0x1 0x1

• Specifies DSP enabled system compliance:
• 1. Non-UAA (IntelSST driver support only)
• 2. UAA (HD Audio Inbox or IntelSST driver support)

• Audio DSP is unusable on Linux with SOF with Intel MEI disabled

• Default: UAA (HDA Inbox/IntelSST) 1
• Ideal: UAA (HDA Inbox/IntelSST) 1

setup_var_cv Setup 0xF49 0x1 0x1

• Enable/Disable Overclocking Lock (BIT 20) in FLEX_RATIO(194) MSR

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x659 0x1 0x0

• Configure MSR 0xE2[15], CFG Lock bit

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x5BD 0x1 0x0

• Select DVMT 5.0 Pre-Allocated (Fixed) Graphics Memory size used by the Internal Graphics Device

• Default: Unknown
• Ideal: 64M 2

setup_var_cv Setup 0x8D2 0x1 0x2

• Select DVMT5.0 Total Graphic Memory size used by the Internal Graphics Device

• Default: Unknown
• Ideal: MAX 3

setup_var_cv Setup 0x8D3 0x1 0x3

• Enable/Disable above 4GB MemoryMappedIO BIOS assignment
• This is enabled automatically when Aperture Size is set to 2048MB

• Default: Disabled 0
• Ideal: Enabled 1

setup_var_cv Setup 0x8D7 0x1 0x1

• Select the Aperture Size

• Default: 256MB 1
• Ideal: 2048MB 15

setup_var_cv Setup 0x821 0x1 0xF

• Enable PCH to aggressively enter link power state

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0xA7E 0x1 0x0

• Enable/Disable CSM Support

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x11A6 0x1 0x0

• Default: COM1 2
• Ideal: Disabled 0

setup_var_cv Setup 0x13DD 0x1 0x0

• Default: Default Max Frequency 255
• Ideal: 1200Mhz 24

setup_var_cv Setup 0x82B 0x1 0x18

• FCLK frequency can take values of 400MHz, 800MHz and 1GHz
• (1GHz not supported for ULT/ULX SKUs)

• Default: Normal (800MHz) 0
• Ideal: 1GHz 1

setup_var_cv Setup 0x66F 0x1 0x1

• Maximum Value of TOLUD
• Dynamic assignment would adjust TOLUD automatically based on largest MMIO length of installed graphic controller

• Default: EFI Driver 1
• Ideal: Auto 0

setup_var_cv Setup 0x10D0 0x1 0x0

• If Auto, only install Legacy OpRom with Legacy OS and logo would NOT be shown during post.
• Efi driver will still be installed with EFI OS.

• Default: Dynamic 0
• Ideal: 3.5 GB 11

setup_var_cv Setup 0x90E 0x1 0xB

• Use RST Legacy OROM when CSM is Enabled
• Test if this allows Legacy booting on NVMe

• Default: Disabled 0
• Ideal: Enabled 1

setup_var_cv Setup 0xA7A 0x1 0x1

• Enable/Disable Intel Rapid Recovery Technology

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0xA72 0x1 0x0

• Check to enable render standby support

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x81B 0x1 0x0

• When a processor thermal sensor trips (either core), the PROCHOT# will be driven
• If bi-direction is enabled, external agents can drive PROCHOT# to throttle the processor

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x5F4 0x1 0x0

• Enable/Disable PROCHOT Lock
• TODO: This was already disabled?

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x5F7 0x1 0x0

• Configure BIOS Guard feature
• This may cause BIOS updates to fail when it tries to update BIOS Guard

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x1177 0x1 0x0

• Select the LCD panel scaling option used by the Internal Graphics Device

• Default: Auto 0
• Ideal: Off 1

setup_var_cv Setup 0x81A 0x1 0x1

• Enable/Disable WatchDog Timer

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0x7D1 0x1 0x0

• Enable or Disable the High Precision Event Timer

• Default: Enabled 1
• Ideal: Disabled 0

setup_var_cv Setup 0xA0A 0x1 0x0

• The control of Active State Power Management of the DMI Link

• Default: Auto 4
• Ideal: Disabled 0

setup_var_cv Setup 0xEE6 0x1 0x0

• Enable/Disable the control of Active State Power Management on SA side of the DMI Link
• SA is System Agent?

• Default: L0sL1 3
• Ideal: Disabled 0

setup_var_cv Setup 0x900 0x1 0x0

• https://github.com/erpalma/throttled/issues/97
• https://github.com/mihic/linux-intel-undervolt
• https://github.com/erpalma/throttled/blob/master/throttled.py

• ThrottleStop: FIVRVoltage00=0xF3200000
• -100.6 mV Offset Voltage

wrmsr --all '0x150' '80000011F3200000'

• ThrottleStop: IccMaxNew00=0x000003FF
• 255.75 A

wrmsr --all '0x150' '0x80000017000003ff'

• ThrottleStop: FIVRVoltage20=0xF3200000
• -100.6 mV Offset Voltage

wrmsr --all '0x150' '80000211F3200000'

• ThrottleStop: IccMaxNew20=0x000003FF
• 255.75 A

wrmsr --all '0x150' '0x80000217000003ff'

• ThrottleStop: FIVRVoltage40=0xF3200000
• -100.6 mV Offset Voltage

wrmsr --all '0x150' '80000411F3200000'

• ThrottleStop: IccMaxNew40=0x000003FF
• 255.75 A

wrmsr --all '0x150' '0x80000417000003ff'