Addressing System Board Components - HP Vectra XU5 Reference Manual

Addressing System Board Components

This section provides more details on how the BIOS uses the system board components
mentioned in the I/O port list.
DMA Channel Controllers
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 only types of DMA transfer
allowed are "I/O-to-memory" and "memory-to-I/O".
"I/O-to-I/O" and "memory-to-memory" transfers are disallowed by the hardware
configuration. The following table summarizes how the DMA channels are allocated.
DMA Channel Allocation
First DMA controller (used for 8 bit transfers):
Channel Function
0 Available
1 ECP mode for parallel port
2 Flexible disk I/O
3 Available
Second DMA controller (used for 16 bit
transfers):
Channel Function
4 Cascade from first DMA controller
5–6 Available
6–7 Available
Vectra XU Technical Reference Summary of the HP BIOS 54