Select the product you need help with
- Internet Explorer
- Windows Phone
- More products
"ACPI BIOS is attempting to write to an illegal IO port address" error message when you open the event viewer
Article ID: 283649 - View products that this article applies to.
This article was previously published under Q283649
The following error message may be in the system event log when you open the event viewer:
Where nnnn is one of the following:
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:
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.
Contact the BIOS vendor for a possible BIOS update. For more information, visit the following Microsoft Web site: