ATI Cards Use EISA I/O Addresses in Windows NT

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1

SYMPTOMS

Windows NT may report I/O errors on EISA machines when an ATI card is present.

The ATI cards use many addresses across the I/O space, and infringe on Extended Industry Standard Architecture (EISA) addresses. This will cause address conflicts with EISA cards. This problem has been noted with the Adaptec 174x series and the Ultrastor.

WORKAROUND

To work around this problem, move an EISA host adapter (for example, from slot 1 to slot 3) so a different EISA address space (3C00 instead of 1C00) will be used.

The ATI adapter uses EISA address space for its extended registers.

In MS-DOS, Windows, and OS/2, this problem can go unnoticed because they don't check all I/O ranges. The miniport driver under Windows NT reports the I/O that you will be using to access the hardware. Windows NT keeps track of it. When the ATI card starts claiming the same I/O ranges, the error gets reported under Event Viewer.

EISA specifications state that slot #1 uses addresses 1C00 - 1CFF, slot #2 uses 2C00 - 2CFF, slot #3 uses 3C00-3CFF, and so on.

ISA uses address 00 - FF for I/O devices integrated onto the system board and 100h - 3FFh for I/O expansion cards. 400 - FFFFh are reserved.

There is nothing that can be fixed since EISA host adapters have to use EISA address space (in fact, 1C80-1C83 are used to store card's ID for slot 1, 2C80-2C83 for slot 2 ID).

The Adaptec and Ultrastor products included here are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.