I received this interesting bit of info from IceCool concerning the Boot Lock and possibly the extra ROM socket:

I noticed the mystery bootblock jumpers among the pics so I thought I'd clear this up.   The 29F series flash memories are divided into a number of sectors - the first sector or better the so called bootsector (or loader) is usually the same size (64K) as the others followed by a smaller one. This bootsector is called rightfully the "loader" as it contains the basic input
output system commands (BIOS) for the relevant microcontroller to "boot" the machine - which does not mean load the OS, but simply load the first initial commands to setup for the actual boot, which in this case would be the OS load. Now as you may have understood this is very critical as if it gets corrupted the machine is dead and you need to reflash the loader with external hardware or, in the case of the MPC use the special empty ROM socket for this purpose (I bet it is there for this reason). This is what that bootblock protect jumper is for (bootlock) - it write protects the loader area so that it is safe from any malfunction of the OS (no writing in that area even if you want to). The write enable is set only when the MPC first comes out of the plant and the xfer the loader on the flash using the eeprom socket and then removing it and write protecting it (in fact on the pcb I did not see and other debug port for this purpose).
I hope this wasn't confusing and cleared some doubts.

One further note: it is possible that one of the jumpers may allow you to restore the loader from floppy - but this would indicate the need of additional ROM to accomplish this so I wouldn't be too certain about this (for ex. most new Motherboards allow you to recover a corrupted bios flash by putting on the disk DOS + flash utility and bin file to prevent the need for external reprogramming of the flash).

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