MCPX stands for "Macintosh Common Peripheral eXtensions," which was a set of peripherals and firmware developed by Apple in the early 1990s. The MCPX Boot ROM Image refers to the read-only memory (ROM) image used to boot devices equipped with these peripherals. The Boot ROM Image contains the firmware necessary to initialize and configure the device's hardware during the boot process.
The MCPX Boot ROM Image is a tiny fossil that explains an entire generation of console security. It tried to be a steel vault, but one misplaced jump instruction turned it into a screen door. Mcpx Boot Rom Image
Decrypting the Second-Stage Bootloader (2BL) from the flash ROM and transferring control to it. xboxdevwiki How to Obtain the Image Mcpx Boot Rom Image