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DMA Addresses and NewWorld Software

In the past, Macintosh computers that use the PCI bus had a one-to-one correspondence between physical addresses and logical addresses as long as VM was off. To allow DMA transfers with VM on, DMA device drivers made a call to the PrepareMemoryForIO function to set up physical and logical mapping for their memory buffers. On Macintosh computers that use the NewWorld software, DMA device drivers must always make that call, whether VM is on or off. Information about how to use the PrepareMemoryForIO function appears on pages 219-229 of Designing PCI Cards and Drivers for the Power Macintosh .