If you are experimenting with your old Mac then you may want to have a tool called Mac EFI Toolkit in your arsenal of important tools. This small tool can be used to open, read, repair, patch and manually edit the EFI ROM.
Mac EFI Toolkit is a portable application for Windows. It works flawlessly on all versions of Windows without having to install anything. Since it is a Windows application, we can guess that it is of particular interest to the people who use or modify Hackintosh.
We begin by opening the UEFI BIOS firmware dump in Mac EFI Toolkit. It supports many different formats for the firmware file such as BIN, ROM, FS, and BIO. It works with all the firmware dumps from all the latest Mac versions.
When a firmware is opened using Mac EFI Toolkit, it displays the firmware file information such as the size, date on which it was created, date on which it was modified and the CRC32 checksum. The modified date and file checksum can be a good indication that the file has been modified and is no longer the original untouched firmware.
From the firmware file, it can decipher the Mac model for which the firmware is meant, the serial number, the EFI version, the board ID for which the firmware was meant, whether its EFI is locked or unlocked and if the firmware has a driver (APFS DXE) present inside.
In addition to editing the different values and unlocking a firmware, it can also be used to patch the firmware for a particular device. In the settings for Mac EFI Toolkit, we can choose to enable or disable the LZMA compression so that compressed firmware can be opened and the drivers present can be checked.
You can download Mac EFI Toolkit from https://github.com/MuertoGB/MacEfiToolkit.