The MPC106, codenamed "Grackle", is a PCI bridge/memory controller. Its predecessor was the MPC105, codenamed "Eagle". It replaced an Apple-made host bridge codenamed "Bandit", part number 343S1125.
Unlike the CPU, which generally runs in big-endian mode, the Grackle runs in little-endian mode in compliance with the PCI standard. This usually means that to get the result in the correct endian, the PowerPC must load and store byte-reversed inputs and results.
CONFIG_ADDR can be found at any address in the range 0xFEC00000–0xFEDFFFFF, while CONFIG_DAT can be found at any address in the range 0xFEE00000–0xFEEFFFFF. The device trees also establish 0xFEF00000 as the 8259 interrupt acknowledgement register.
The dingusppc CLI can add known PCI devices to a PCI slot (A1, B1, C1).
Only the following device numbers are probed by Open Firmware:
-@0 used by pci [grackle]
-@c slot PERCH interrupt 0x1c
-@d slot A1 interrupt 0x17
-@e slot B1 interrupt 0x18
-@f slot C1 interrupt 0x19
-@10 used by mac-io [heathrow] which includes many devices with different interrupts
-@12 slot F1 interrupt 0x16 used by AtiRageGT or AtiRagePro
With minor additions to source code, dingusppc can add a known PCI device to any device number between @1 and @1f except for @10 and @12.
A nvramrc patch can make Open Firmware probe the other device numbers. An OS might be able to probe these other devices numbers even if they are not probed by Open Firmware.