IBM 689912U - IntelliStation Z - Pro 6899, Hardware Maintenance Manual

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Ÿ
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:
Ÿ
Accesses the memory by bypassing the
processor, which allows the processor more time for
applications and programs.
Ÿ
Accesses memory directly from the serial and parallel
ports on some systems.
Ÿ
Accesses memory directly from some adapters
using a DMA channel, which allows the adapter to
operate faster.
Ÿ
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, the:
Ÿ
ROM contains operating instructions for the adapter
I/O.
Ÿ
RAM is used for buffering.
Two adapters using the same memory area will cause
a failure. This failure might appear as a hardware failure.
The IRQ levels, DMA channels, I/O address, and ROM
and RAM addresses all become potential conflicts and
system problems. When conflicts arise, they might show
up as system hangs, lost or missing devices, incorrect or
bad data, or failing diagnostics. Always eliminate
conflicts in these areas before replacing any hardware
components.
Reference Information
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