108
5 HP BIOS
BIOS Addresses
DMA Channel Controllers
Only “I/O-to-memory” and “memory-to-I/O” transfers are allowed.
“I/O-to-I/O” and “memory-to-memory” transfers are disallowed by the
hardware configuration.
The system controller supports seven DMA channels, each with a page
register used to extend the addressing range of the channel to 16 MB.
The following table summarizes how the DMA channels are allocated.
03F8 - 03FF
COM1
04D0 - 04D1
Interrupt edge/level control
0678 - 067B
LPT2 ECP
0778 - 077B
LPT1 ECP
0CF8 - 0CFF
PCI configuration space
C000 -
Power Management I/O space and ACPI Registers
C100 -
MBus I/O space
Default Values for
I/O Address Ports
Function
DMA controller
Channel
Function
DMA 0
Free
DMA 1
Free if not used for parallel port in
Setup
DMA 2
Floppy disk drive controller
DMA 3
Free if not used for parallel port in
Setup
DMA 4
Used to cascade DMA channels 0-3
DMA 5
Free
DMA 6
Free
DMA 7
Free