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PCI/I-486SP3G
User's Manual
Assigning System /Ras
Both the ISA
and PCI
buses may need to use
IRQs.
You must
con-
figure any IRQ assignments so
that the
system can
know which bus
is
using
a
particular IRQ. You must
assign
IRQs
correctly, or
the
mainboard will not work properly.
As mentioned
in Chapter 1, there
are
16 IRQs
available.
In an ISA
design,
some of
them
are already
in use by
standard
parts of the
sys-
tem
such as the keyboard
or
mouse.
Drawing
from the unused
group
of
System IRQs,
you can assign an
IRQ to
either
bus.
Since
both bus
designs use IRQs,
we differentiate
them by
referring
to the IRQs
as-
signed
to the ISA bus
as
ISA
IRQs and
to the PCI bus as PCI IRQs.
There is
an
IRQ reference
chart
in
Chapter 4.
The two bus designs
deal
with IRQs differently. In the ISA bus,
the IRQs
are available
to
every slot and
you define which IRQ is in
use by
configuring
the IRQ number
on
the
expansion card you want
to install. You
can
then install the
card
in any
available slot.
In the PCI design
you assign an
IRQ to
a PCI slot
rather than
doing
it
on a card. For PCI cards, you only
need
to set something
called the "INT"
assignment. Since all
the PCI
slots
on this mainboard
use "INTA#",
you only
need to make
sure
that
any
PCI card you in-
stall
is
set
to INT
A.
Of the
PCI cards
that use an IRQ, the
overwhelm-
ing majority of them use
a
level-triggered IRQ design. You
can assign
IRQs for this type
of card
by using the BIOS
Setup
Utility.
See the
section on
PCI
Slot Configuration
in
Chapter 3.
Some very
few PCI
cards use
an edge-triggered
IRQ design.
For
these
you
have to
assign
the
PCI Slot
IRQ by
also setting a
jumper
in
jumper
blockJPl-10.
The block
sets
the assignments for IRQs 5, 9, 11,
14, and 15. These jumpers only assign
IRQs
for edge-triggered cards.
Their default settings
leave
the five IRQs unassigned and available
to either the ISA bus or level-triggered PCI cards.
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2-4
Upgrade Guide
~
You do not need to
assign
a System IRQ to
a
PCI
slot
unless
you
install a
card
in it that needs an
IRQ.
If you don't
assign a
System
IRQ to
a
PCI slot in the Setup Utility, the unused IRQS
are
available
to the ISA bus.
Selecting IRQ Settings for Edge-Triggered Cards
Set the IRQ
for edge-triggered cards
both in the Setup Utility and
on the board using the JPl-10 jumper block. The chart below
shows
the setting options and the figure below it the defaults. Don't u
se
the
SCSI settings.
System
Default
PCI Bus edge trigger IRO settings
IRO
setting
PCI 1
PCl2
PCI 3
IRQ 5
JP1&6 2-3
JPl 1-2
JPl 3-4
JP61-2
IRQ 9
JP2&7 2-3
JP21-2
JP2 3-4
JP7 1-2
IRQ 11
JP3&8 2-3
JP31-2
JP3 3-4
JPS 1-2
IRQ 14
JP4&9 2-3
JP4 1-2
JP4 3-4
JP91-2
IRQ 15
JP5&10 2-3
JP51-2
JP5 3-4
JP10 1-2
Note: You can only select one option for each IRO.
JP6
JPl
JP7
JP2
JPS
JP3
JP9
JP4
JPlO
JP5
-cnz
--o --o --o
Znn Zn Zn Zn
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-le:;)
-l;;::) -;:::;
IRQ5
IRQ9
IRQ11
IRQ14
IRQ15
0 880
0 880
OGeO
0 Gf)O
OGeO
0 880
0 880
0 880
0 880
0 880
IRQ5
IRQ9
IRQ11
IRQ14
IRQ15
NCR SCSI
JP6 3-4
JP7 3-4
JPS 3-4
JP9 3-4
JP10 3-4
D
Default settings leave
the
IRQs listed
available
for level-triggered or ISA
bus expansion cards.
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2-5
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