Addressing System Board Components - HP Vectra VL5 4 Technical Reference Manual

ADDRESSING SYSTEM BOARD COMPONENTS

This section provides more details of 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.
First DMA controller (used for 8-bit transfers)
Channel Function
0 Available
1 Available or ECP mode for parallel port
2 Flexible disk I/O
3 Available or ECP mode for parallel port
Second DMA controller (used for 16-bit transfers)
Channel Function
4 Cascade from first DMA controller
5-6 Available
6-7 Available