AmigaOne Megarray adapter

As I understand, some PowerMacs use the same Megarray 300pin connector as was used in AmigaOnes, but the pinout is different. So, one must determine the connections from Megarray to CPU for both kinds of modules, and make an adapter which rewires the motherboard connector to the connections a PowerMac module expects. So, our goal is to allow AmigaOne XE and MicroA1 owners to install something like this from Apple land, either to replace a dead AmigaOne CPU module, or simply to increase performance as so many of us have done with our "Classic" Amiga computers using CPU Accelerator cards. But we may be lucky to get anything good from this anyway, since G4 Macs are getting quite old and these accelerators may not be made anymore and thus become hard to get.

I bought an Apple PowerMac G4 from ebay for cheap. My motherboard is from this model. It has a Freescale XPC7400 CPU chip on the module. This is my first sacrificial item, from the Apple CPU module side of things. While I do also have the motherboard, Apple's proprietary northbridge chips are not documented, so we can't know what a pin connection there is used for, so the CPU module will be the more interesting item to probe.

Thanks to Helge Kvalheim for donating his broken AmigaOne G4 XE board, I can also probe the AmigaOne Megarray connections and hopefully figure out this side of things. It has a 7455 CPU at 933MHz rating.

Here's my Eagle PCB library (LGPL 3+ license) containing layout footprints for 300pin MegArray connector (both plug and receptacle, each on both top and bottom PCB layers):