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Q: I've been getting various reports from users about a problem with Open Firmware on almost all Macintoshes. It appears that Open Firmware is incorrectly assigning the same I/O range to several cards on the same PCI bus. Is this a known bug? A: Apple does not know of any reports concerning Open Firmware incorrectly assigning PCI I/O space. What you may be seeing is two or more PC-compatible "legacy" devices being placed into Macintosh PCI slots. A legacy device could be, for instance, a VGA or IDE controller with hard-coded address assignments previously used on an ISA bus. Since both of these controllers are hard wired to the same physical address in PCI I/O space, their address assignments conflict. There is no work around since both controllers expect to use the same address. This was acceptable when a PC had limited expansion capabilities, but must be taken into account when your personal computer has a PCI bus. For details see "PCI Bus Binding to IEEE Std 1275-1994 Standard for Boot (Initialization Configuration) Firmware Revision 2.1" Section 7, Legacy Devices. For your convenience here is that text:
As you can see, both types of controller expect to be given a physical address range by Open Firmware. You can determine that your device is requesting a non relocatable address range by looking at the |