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"ACPI BIOS is attempting to write to an illegal IO port address" error message when you open the event viewer

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This article was previously published under Q283649
The following error message may be in the system event log when you open the event viewer:
Source: ACPI Category: None Type: Error Event ID: 5 User: N/A Computer: Machine_Name Description: AMLI: ACPI BIOS is attempting to write to an illegal IO port address (0xnnnn), which lies in the 0xXXXX - 0xYYYY protected address range. This could lead to system instability. Please contact your system vendor for technical assistance.

For more information, see Help and Support Center at:
Where nnnn is one of the following:
   Address or Range   Description   0x000 – 0x009      ISA DMA   0x020 – 0x021      PIC   0x040 – 0x043      Timer1, Refresh, Speaker, Control Word   0x048 – 0x04B      Timer2, Failsafe   0x070 – 0x071      CMOS/NMI enable   0x074 – 0x076      Extended CMOS   0x081 – 0x083      DMA   0x087              DMA   0x089              DMA   0x08A – 0x08B      DMA   0x08F              DMA   0x090 – 0x091      Arbitration Control Port, Card Select Feedback   0x093 – 0x094      Reserved, System board setup   0x096 – 0x097      POS channel select   0x0A0 – 0x0A1      Cascaded PIC   0x0C0 – 0x0DF      ISA DMA   0x4D0 – 0x4D1      Edge, level control registers for PIC    0xCF8 – 0xCFF      PCI Configuration Space Access Pair				
This behavior may occur if your computer's basic input/output system (BIOS) tries to write to one of the earlier ports by using an AML [Advanced Configuration and Power Interface (ACPI) Machine Language] System IO operation region. Your try may be blocked by Microsoft Windows XP because accessing these ports by using this mechanism is considered dangerous and can cause system instability. This feature is designed to improve the stability of your computer's operating system.
This behavior is by design.
Contact the BIOS vendor for a possible BIOS update. For more information, visit the following Microsoft Web site:
0x80 0x400 0xcf8 0xcfc

Article ID: 283649 - Last Review: 09/22/2006 03:28:47 - Revision: 3.2

  • Microsoft Windows XP Professional
  • Microsoft Windows XP Home Edition
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