Releases

EnableGop version (OpenCore version)

1.4 (0.9.3)

Incorporates recent updates to OpenCore console control code, but no difference in behaviour compared to version 1.3 is expected on any supported systems.

1.3 (0.9.2)

Included fix to GopBurstMode for non-standard frame buffer information on AMD Radeon HD 7970 and similar
Applied GopBurstMode even on natively supported cards, as it can provide a noticable speed up

1.2 (0.9.1)

Added GopBurstMode support

Note 1: This should provide faster GOP rendering on all EnableGopDirect systems; and rendering at least at the same speed as before, and on some systems noticeably faster than before, on almost all EnableGop systems.

Note 2: The compressed driver for version 1.2 is 1KB larger than for version 1.1, so for AMD GPU firmware which is tight on space version 1.1 may be used instead to avoid the need for VGA stripping to make additional space.

1.1 (0.9.0)

Fixed early verbose boot lines appearing over picker
Added EnableGop version number to UI section

1.0 (0.8.9)

Initial public release

Status

Current status: Beta release.

This driver has been tested and is working on several iMac models with several different GPUs, and on several MacPro4,1/5,1 machines with several different GPUs. However, in the worst case (and still possible) scenario, an incompatible or incorrectly installed driver in firmware may brick your hardware.

In all cases take a backup of the main firmware or GPU firmware which you are modifying, and confirm that you can successfully restore from this, before starting.

Recovery from bricked hardware

If attempting main firmware insertion on a MacPro4,1/5,1, for recovery from a bricked device you will either need a Matt card (which may breach intellectual property laws in some jurisdictions) or the ability to desolder and reprogram your own SPI flash chip.
If testing via main firmware insertion on an iMac, you will need the ability to disassemble your iMac and reprogram its SPI flash chip using a SOIC clip attached to a CH341A controller running on another computer.
If testing via GPU firmware insertion (iMac or Mac Pro), you will need the ability to disassemble your system, likely remove the heat sink from the graphics card, and then reprogram its SPI flash chip using a SOIC clip attached to a CH341A controller running on another computer.
- If testing via GPU firmware insertion, in some cases it may also be possible to use physical electrical connection to your GPU in order to enable booting with no graphics even though the GPU is present, then connect to your machine with ssh (which must have been enabled beforehand) and reprogram the GPU firmware. Advice on this headless boot approach is not provided here, but may be found for instance on the iMac GPU related forum threads listed below.

If you are not familiar with the above procedures, you are strongly recommended to wait for further testing by users who are. No further help can be provided here, and you proceed entirely at your own risk.

Summary

Targetting EFI-era (~2009-2012) MacPro4,1/5,1 and iMac firmware, this driver gathers and injects the parts of OpenCore needed for pre-boot graphics support with non-natively supported GPUs.

The requirements for using this driver are:

EFI-era (~2009-2012) MacPro4,1/5,1 or iMac with most recent main firmware.
A GPU which does not produce native pre-boot graphics (such as native picker when pressing ALT key during boot) before OpenCore starts (otherwise, you do not need it).
A GPU which produces graphics when using OpenCore (this must include successfully showing the native Apple boot picker when started via the latest version of OpenCore tool BootKicker.efi) (otherwise, the driver will not work).
- Note: If your OpenCore installation includes a required GOP driver for your graphics card, then you would also need to burn that driver to the firmware of your graphics card in order to obtain pre-OpenCore graphics; instructions for this are outside the scope of this tutorial, although the procedures required for modifying GPU firmware are similar to what is covered here. Note that such a driver is added by the OCLP Enable AMD GOP option, which is enabled automatically on some systems by recent versions of OpenCore Legacy Patcher, as a way to enable the OpenCore menu in cards such as ex-mining GPUs.

When installed, the driver should enable:

Native boot picker via ALT key
Firmware password UI
Target disk mode UI
macOS boot progress screen
etc.

Compiled versions of the driver files and these instructions may be found in the Utilities/EnableGop directory of the OpenCore release package.

For GPUs needing DirectGopRendering in OpenCore configuration, use EnableGopDirect.efi, otherwise use EnableGop.efi as it renders faster on most other systems.

The driver may be installed to GPU or main motherboard firmware. It is expected that most Mac Pro users will use main firmware insertion and most iMac users will chose GPU firmware insertion, however both techniques work on both systems (but it is harder to modify the iMac main firmware, since there is no simple way to enable writing to it).

Further discussion and community support for this driver is available at:

https://forums.macrumors.com/threads/pre-opencore-gop-support-for-efi-era-imacs-and-mac-pros.2378942/

Usage

Install to main firmware

For reading and writing to main firmware on the Mac Pro, @Macschrauber's Rom Dump works well. Alternatively the kexts and executables which this uses can be sourced individually (or extracted from the Rom Dump app) and run from the command line.

The main firmware on the iMac cannot be updated without an initial hardware flash (SOIC clip plus CH341A controller), therefore the recommended approach on iMac systems is GPU firmware injection. However, the below instructions for firmware injection do work, if you are willing to do a hardware flash of the resulting firmware file, or if you have already unprotected your iMac firmware - which reduces security, and is only recommended for those actively developing firmware modifications.

The .ffs file provided in this directory can be manually added to the extracted firmware file using UEFITool, or automatically added using @dosdude1's DXEInject. Once more, if you are not familiar with these procedures, you are recommended to proceed with extreme caution.

Using DXEInject

To install the driver via DXEInject, the command is:

DXEInject {original}.rom {modified}.rom EnableGop.ffs

The file {modifed}.rom is ready for burning, although the result can be checked using UEFITool, if required.

‍Note: If only reading a file with UEFITool, the latest version is recommended, as it provides the most information. For writing, the older version 0.25.1 must be used, as described below.

Using UEFITool

The .ffs file may be inserted anywhere within the same firmware volume which contains DuetBds (file GUID A6F691AC-31C8-4444-854C-E2C1A6950F92). However, for simplicity, these instructions will insert it in the same place that DXEInject does:

Use UEFITool 0.25.1 (it must be that old version, not the newer NE or new engine versions, which cannot yet edit)
Perform a header-only GUID search for BAE7599F-3C6B-43B7-BDF0-9CE07AA91AA6
Double-click on the search result
Right-click on the DXE driver with that GUID which should then appear
Choose "Insert after..." and select EnableGop.ffs
Save the modified firmware

The end result, after saving and re-loading, should look like this:

Install to GPU firmware

Instructions and a script for inserting the driver into Nvidia or AMD GPU firmware (aka VBIOS) are provided.

Please note all the cautions already given above about the difficulty of recovering, unless you are familiar with the procedures necessary, if this process fails.

To use the provided vBiosInsert.sh script:

Locate an appropriate version of the nvflash tool (Nvidia) or amdvbflash tool (AMD) (both are available for Linux and Windows), which can be used to read from and write to the GPU firmware.
Use that tool to read a copy of the GPU firmware.
Run ./vBiosInsert.sh [-a|-n] {original}.rom EnableGop.efi {modified}.rom, with -a for AMD and -n for Nvidia.
- If you have any problems with vBiosInsert.sh from a specific release of EnableGop, please try the version included with the latest release of OpenCore before reporting any issues. The script receives updates to support additional graphics cards independently of any bumps to the release version of EnableGop. If you need to, you can use the latest version of vBiosInsert.sh to inject older versions of EnableGop.
The new file {modified}.rom may be burnt to the GPU firmware.

In the case of AMD, considerably less space is normally available, due to a strict limit of 128k for legacy and EFI parts of the larger ROM image. If there is not enough space (i.e. script reports data would be truncated) then it is necessary to strip some legacy VGA parts of the GPU firmware. This is beyond the scope of these instructions.

If required to manually detect the GOP offset (this should normally be autodetected):

‍Using a hex editor, search in the GPU firmware dump for the byte sequence F1 0E 00 00 with the byte sequence 55 AA coming close before it; the start address of the 55 AA is the GOP offset value needed.

For further information on GPU firmware modification, see: