Windows NT Parallel Ports Do Not Use Interrupts

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1
• Microsoft Windows NT Workstation versions 3.5, 3.51, and 4.0
• Microsoft Windows NT Server versions 3.5, 3.51, and 4.0

SUMMARY

In Windows NT, parallel ports do not use any hardware interrupt request lines (IRQs).

The Windows NT parallel port driver is thread-based, and the port is polled at background priority. This eliminates a number of potential hardware conflicts with other devices that might want to use IRQ 7 or 5, that used to be the parallel port interrupts.

MORE INFORMATION

If you have applications that run very slow due to large print jobs, you can reduce the thread priority of the port print function by adding the following registry entry:

WARNING: Using the Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

Windows NT 3.51

1. Start Registry Editor (Regedt32.exe) and locate the following key:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print

2. Add the following value:

         Key:   PortThreadPriority
         Type:  REG_SZ
         Value: Thread_Priority_Below_normal
   
   

3. Quit Registry Editor.

Windows NT 4.0

1. Start Registry Editor (Regedt32.exe), and locate the following key:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print

2. Add or change the following value:

         Key:   PortThreadPriority
         Type:  REG_DWORD
         Value: -1
   
   

3. Quit Registry Editor.

Keywords          : ntprint NTSrvWkst kbprint
Version           : WinNT:3.1,3.5,4.0
Platform          : winnt