dingusppc/zdocs/grackle.md

The MPC106, codenamed "Grackle", is a PCI bridge/memory controller. Its predecessor was the MPC105, codenamed "Eagle".

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.

By default, Grackle operates on Address Map B.

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.

PCI Config addresses work as follows:

bus << 16 | device << 11 | function <<  8 | offset

# Revisions

Revisions under 4.0 could allow up to 75 MHz, whereas 4.0 and newer can allow up to 83 MHz.

# General Data

Vendor ID: 0x1057 (Motorola)
Device ID: 0x0002 (MPC106)

Within the Mac's own device tree, this is usually device 0.

It also spans for 0x7F000000 bytes starting from 0x80000000.