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Intel Framebuffer Patching Reference Guide

Based on Info extracted from: https://github.com/acidanthera/WhateverGreen/blob/master/Manual/IntelFramebuffer.bt

1. Connector Types

Hex Value Name Description Common Use
0x0 ConnectorZero Zero/disabled Unused connectors
0x1 ConnectorDummy Dummy connector Sometimes works as VGA
0x2 ConnectorLVDS LVDS/eDP Built-in laptop displays
0x4 ConnectorDigitalDVI Digital DVI DVI-D ports (NOT eDP)
0x8 ConnectorSVID S-Video Legacy video output
0x10 ConnectorVGA VGA Analog VGA ports
0x400 ConnectorDP DisplayPort DisplayPort outputs
0x800 ConnectorHDMI HDMI HDMI ports (enables digital audio)
0x2000 ConnectorAnalogDVI Analog DVI DVI-A/DVI-I ports

Important Notes:

  • Connector type is less critical on newer hardware (Skylake+)
  • VGA can work via DP on Kaby Lake
  • Index 0 (LVDS) gets special treatment as built-in display

2. BusID Values (GMBUS IDs)

BusID Linux Name Description Typical Use
0x00 Special Internal display Built-in laptop displays
0x02 GMBUS_PIN_VGADDC VGA DDC VGA ports (pre-Skylake)
0x04 GMBUS_PIN_DPC HDMIC HDMI/DP port C
0x05 GMBUS_PIN_DPB SDVO/HDMIB HDMI/DP port B, DVI via SDVO
0x06 GMBUS_PIN_DPD HDMID HDMI/DP port D

Best Practices:

  • Use 4, 5, 6 for arbitrary HDMI/DisplayPort displays
  • BusID 5 supports SDVO (can handle DVI)
  • Skylake+ uses SDVO for VGA instead of dedicated pin

3. Connector Flags

Hex Value Flag Name Effect When to Use
0x1 CNAlterAppertureRequirements Removes aperture memory requirement Special configurations
0x8 CNConnectorAlwaysConnected Marks connector as always connected Built-in displays (LVDS)
0x40 CNDisableBlitTranslationTable Disables blit translation Special cases
0x80 CNUseMiscIoPowerWell Activates MISC IO power well Additional power requirements
0x100 CNUsePowerWell2 Activates Power Well 2 Fixes HDMI audio issues
0x800 CNIncreaseLaneCount Increases lane count to 30 (vs 20) High bandwidth displays

Common Values:

  • 0x00000000 - Standard external display
  • 0x00000008 - Built-in display (always connected)
  • 0x00000108 - External display with HDMI audio fix

4. Framebuffer Flags

Critical Flags for Patching

Hex Value Flag Name Effect
0x1 FBAvoidFastLinkTraining Disables fast link training (450MHz vs 540MHz)
0x2 FBFramebufferCommonMemory Stolen memory counts all FBs at once (not per-FB)
0x4 FBFramebufferCompression Enables framebuffer compression
0x8 FBEnableSliceFeatures Enables slice features (Slice SD, EU SD, Dynamic Slice)
0x10 FBDynamicFBCEnable Enables dynamic framebuffer compression
0x20 FBUseVideoTurbo Enables GPU turbo frequency (default: 14)
0x40 FBForcePowerAlwaysConnected Forces power reset on always-connected displays
0x80 FBDisableHighBitrateMode2 Limits DP to 8.64 Gbit/s (HBR1 vs HBR2)
0x100 FBBoostPixelFrequencyLimit Boosts pixel clock to 540MHz
0x200 FBLimit4KSourceSize Limits source size to 4096×4096
0x400/0x800 FBAlternatePWMIncrement Changes backlight PWM (for laptops only)
0x1000 FBDisableFeatureIPS Disables Intermediate Pixel Storage
0x4000 FBAllowConnectorRecover Allows connector recovery (Camellia v2)
0x200000 FBEnableDynamicCDCLK Enables dynamic CD clock
0x800000 FBSupport5KSourceSize Enables 5K support (5120×5120)

5. Memory Calculations

Stolen Memory Formula (Haswell/Broadwell)

TotalStolen = 0x100000 (1 MB base)
+ (FBFramebufferCommonMemory ? StolenMemorySize : StolenMemorySize × FBMemoryCount)
+ FramebufferMemorySize

Stolen Memory Formula (Skylake+)

TotalStolen = 0x100000 (1 MB base)
+ (FBFramebufferCommonMemory ? StolenMemorySize : StolenMemorySize × FBMemoryCount)
+ (FBFramebufferCompression ? FramebufferMemorySize : 0)

Additional Memory

CursorMemory = PipeCount × 0x80000
MaxStolen = (StolenMemorySize × FBMemoryCount) + FramebufferMemorySize + 0x100000
MaxOverall = CursorMemory + MaxStolen + (PortCount × 0x1000)

BIOS Setting: TotalStolen must be ≤ DVMT Pre-Allocated memory in BIOS

6. Connector Structure (Standard)

Offset Size Field Description
0x00 1 byte index Connector index (0-3, or 0xFF for disabled)
0x01 1 byte busId GMBUS ID (see BusID table)
0x02 1 byte pipe Pipe number
0x03 1 byte pad Padding (must be 0)
0x04 4 bytes type Connector type (see Connector Types)
0x08 4 bytes flags Connector flags

Total Size: 12 bytes per connector

Ice Lake Connector Structure (Wide Format)

Offset Size Field
0x00 4 bytes index
0x04 4 bytes busId
0x08 4 bytes pipe
0x0C 4 bytes pad
0x10 4 bytes type
0x14 4 bytes flags

Total Size: 24 bytes per connector

7. Common Patching Scenarios

Enable HDMI Audio

Problem: No audio through HDMI/DP
Solution: Set connector flag 0x100 (CNUsePowerWell2)

Disable Unused Connectors

Problem: Too many connectors detected
Solution: Set connector index to 0xFF (255)

Fix 4K Display Support

Problem: 4K display won't work
Solution:

  • Set flag 0x800000 (FBSupport5KSourceSize)
  • Or remove flag 0x200 (FBLimit4KSourceSize)

Fix Internal Display (Laptop)

Problem: Built-in display not detected
Solution:

  • Set connector type to 0x2 (LVDS)
  • Set connector flag to 0x8 (CNConnectorAlwaysConnected)
  • Set index to 0x0
  • Set busId to 0x0

Increase Stolen Memory

Problem: Graphics glitches, insufficient VRAM
Solution: Increase fStolenMemorySize value (must match/be under BIOS DVMT setting)

8. Generation-Specific Default IDs

Generation Default Platform ID Note
Sandy Bridge Model-dependent See board-id mapping
Ivy Bridge Various No universal default
Haswell Various No universal default
Broadwell Various No universal default
Skylake 0x19120000 Without AAPL,ig-platform-id
Kaby Lake 0x59160000 Without AAPL,ig-platform-id
Coffee Lake 0x3EA50000 Without AAPL,ig-platform-id
Cannon Lake 0x5A520000 Without AAPL,ig-platform-id
Ice Lake 0x8A520000 (Real) 0xFF050000 for simulator

9. Port Type Conversion (Skylake+)

Connector Index Connector Type Resulting fPortType
0 (any type) Any 3 (Internal)
1-3 ConnectorHDMI (0x800) 1 (HDMI)
1-3 Other types 2 (DisplayPort-like)

10. Quick Reference: Common Hex Patches

Connector Example (Hex Format)

Index BusID Pipe Pad  Type      Flags
01    05    09   00   00040000  00000000

Represents: Index 1, BusID 5, Pipe 9, DVI type, no flags

Disable Connector

FF    00    00   00   00000000  00000000

HDMI with Audio

01    06    09   00   00080000  00010000

Index 1, BusID 6, Pipe 9, HDMI, with Power Well 2

Internal Display

00    00    00   00   00020000  00000008

Index 0, BusID 0, Pipe 0, LVDS, always connected

Notes

  • All values are little-endian in actual patches
  • Framebuffer patches require WhateverGreen.kext
  • Always backup original kext before patching
  • BIOS DVMT settings must accommodate stolen memory requirements