Addressing System Board Components - HP Vectra VT6 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
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 pageregister used to extend the
addressing range of the channel to 16 MB. The following table summarizes how the DMA channels
are allocated.
First DMA controller (used for 8-bit transfers)
Channel Function
0 Available
1 SoundBlaster or ECP mode for parallel port
2 Flexible disk I/O
3 ECP mode for parallel port or SoundBlaster
Second DMA controller (used for 16-bit transfers)
Channel Function
4 Cascade from first DMA controller
5 SoundBlaster or Available
6 Available or SoundBlaster
7
Available
Interrupt Controllers
The system has two 8259A compatible interrupt controllers. They are arranged as a master
interrupt controller and a slave that is cascaded through the master.
The following table shows how the master and slave controllers are connected. The Interrupt
Requests (IRQ) are numbered sequentially, starting with the master controller, and followed by the
slave.
IRQ (Interrupt Vector)
IRQ0(08h)
IRQ1(09h)
IRQ2(0Ah) Slave IRQ
IRQ8(70h)
IRQ9(71h)
IRQ10(72h)
IRQ11(73h)
IRQ12(74h)
IRQ13(75h)
IRQ14(76h)
IRQ15(77h)
Interrupt Request Description
System Timer
Keyboard Controller
Cascade connection from INTC2 (Interrupt Controller 2)
Real Time Clock
Available for accessory board (ISA/PCI)
SoundBlaster3, or Available for accessory board (ISA/PCI)
Available for accessory board (ISA/PCI)
Mouse, or ISA accessory board
Co-processor
IDE, or ISA accessory board
2nd IDE or ISA/PCI accessory board