System resource conflicts, System, Resource – IBM 6643 User Manual
Page 117: Conflicts
v
Multiple
messages
occur
when
the
first
error
causes
additional
errors.
Follow
the
suggested
action
of
the
first
error
displayed.
System
resource
conflicts
System
failures
occur
when
there
are
system
resource
conflicts
with
the
following:
v
Interrupt
Request
Queue
(IRQ)
v
Direct
Memory
Access
(DMA)
v
I/O
Address
v
ROM
and
RAM
Addresses.
IRQ
v
Assigns
a
unique
interrupt
request
line
to
every
I/O
device
(line
numbers
range
from
0
to
15).
v
Interrupts
the
processor
to
force
it
to
service
the
request.
v
Handles
interrupts
on
a
priority
basis
(low
numbers
have
the
highest
priority).
v
Queues
interrupt
request.
IRQ
conflicts
occur
when
there
are
multiple
assignments
to
the
same
interrupt
level.
If
there
is
an
IRQ
conflict,
the
system
will
hang.
Use
the
systems
diagnostics
to
check
for
multiple
assignments
to
the
same
interrupt
level
before
replacing
any
hardware
component.
DMA
v
Accesses
the
memory
by
bypassing
the
processor.
This
allows
the
processor
more
time
for
applications
and
programs.
v
Accesses
memory
directly
from
the
serial
and
parallel
ports
on
some
systems.
v
Accesses
memory
directly
from
some
adapters
using
a
DMA
channel.
This
allows
the
adapter
to
operate
faster.
v
Provides
from
4
to
15
DMA
channels.
The
number
varies
depending
on
the
system.
If
multiple
assignments
of
the
same
DMA
channel
occur,
the
system
will
hang.
Use
the
system
diagnostics
to
check
for
multiple
assignments
to
the
same
DMA
channel
before
replacing
any
hardware
components.
I/O
address
A
unique
I/O
address
is
assigned
to
each
system
component.
If
multiple
assignments
of
the
same
I/O
address
occur,
the
system
will
hang.
Use
the
DOS
MEM
command
to
check
for
multiple
assignments
to
the
same
I/O
address
before
replacing
any
hardware
component.
ROM
and
RAM
Addresses
Adapter
cards
with
processors
can
contain
RAM
and
ROM.
If
the
adapter
cards
have
onboard
memory,
then
the
following
are
true.
v
ROM
contains
operating
instructions
for
the
adapter
I/O.
v
RAM
is
used
for
buffering.
Two
adapters
using
the
same
memory
area
will
cause
a
failure.
This
failure
might
appear
as
a
hardware
failure.
Chapter
8.
Related
service
information
109