Problem Using Mach32 ISA Display Adapter on PCI Bus

Last reviewed: September 22, 1995
Article ID: Q137153

The information in this article applies to:

Microsoft Windows 95

SYMPTOMS

If you replace an ATI PCI Mach32 display adapter with an ISA Mach32 display adapter on certain computers with a PCI bus, the computer may stop responding (hang) after the logo screen appears when you start Windows 95.

CAUSE

This problem occurs because of a hardware problem on the PCI bus.

RESOLUTION

The only workaround for this problem is to use the PCI Mach32 display adapter instead of the ISA display adapter.

MORE INFORMATION

To determine whether a computer has this problem, follow these steps:

Restart the computer at a command prompt. To do so, restart the computer, press the F8 key when you see the "Starting Windows 95" message, and then choose Command Prompt Only from the Startup menu.
At the command prompt, type the following line and then press ENTER:
```
      debug
```
At the "-" prompt, type the following line and then press ENTER:
```
      I 3c0
```
If the result is 0, the computer has the problem described in this article. A typical result is 20h on most computers.
Type "q" (without quotation marks) and then press ENTER.
Restart the computer normally.

On computers that have this problem, the attribute controller does not preserve the bit flag indicating that the screen is in. It instead returns a flag indicating that the screen is off. When Windows 95 starts, the virtual display driver reads this value into memory and then later restores the value to the port. Since it reads a value of 0 and restores a value of 0, the screen is turned off.

KBCategory: kbhw
KBSubcategory: win95
Additional reference words: 95

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Last reviewed: September 22, 1995
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