Chapter 3 Hardware Description
10
TI6NB Pentium II 440BX ATX Motherboard User’s Manual
3.6 DMA Channels
There are seven DMA channels available on the motherboard. Only
DMA2 is used by the floppy controller. In the case that ECP mode on the
parallel port is utilized, DMA1 or DMA3 will be used.
3.7 Interrupt Request (IRQ) Lines
There is a total of 15 IRQ lines available on the motherboard. Peripheral
devices use an interrupt request to notify the CPU for the service
required. The following table shows the IRQ lines used by the devices on
the motherboard:
Level Function
IRQ0
System Timer Output
IRQ1
Keyboard
IRQ2
Interrupt
Cascade
IRQ8
Real Time Clock
IRQ9
Software Redirected to Int 0Ah or PCI Slot Int#
IRQ10
Reserved or PCI Slot Int#
IRQ11
Reserved or PCI Slot Int#
IRQ12
PS/2 Mouse or PCI Slot Int#
IRQ13
Co-Processor
IRQ14
Primary IDE
IRQ15
Secondary IDE
IRQ3
Serial Port #2
IRQ4
Serial Port #1
IRQ5
Parallel Port #2 or PCI Slot Int#
IRQ6
Floppy Disk Controller
IRQ7
Parallel Port #1
3.8 Onboard PCI-IDE
The PCI-IDE controller is a part of the 82440BX PCIset. It supports PIO
mode 3/4 and bus mastering Ultra DMA/33. The peak transfer rate of
PIO mode 3/4 can be as high as 17MB/sec. Using HDDs that support
Ultra DMA/33, the peak transfer rate can reach 33MB/sec. There are two
IDE connectors - primary IDE and secondary IDE. With two devices per
connector, up to four IDE devices can be supported.
