Control NT Print Priority

In NT and Windows 2000, parallel ports do not use IRQs but are thread-based. The
port is polled at background priority. This eliminates hardware conflicts with
devices that want to use IRQ 7 or 5, ports that DOS and Win3.x used for the
parallel port interrupts. If an application is running very slow due to large
print jobs, you can reduce the thread priority of the port print function by
adding the following registry entry. You can also use the this registry tip to
increase priority for printing:

WINDOWS NT 3.51
Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Control\Print
Name:
PortThreadPriority
Type: REG_DWORD
Value: Thread_Priority_Below_normal

WINDOWS NT 4.0
Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Control\Print
Name:
PortThreadPriority
Type: REG_DWORD
Value: -1
where the default value in NT 4.0 is 0, which
equals THREAD_PRIORITY_NORMAL. The value for THREAD_PRIORITY_ABOVE_NORMAL is 1
(increase parallel port’s priority) and THREAD_PRIORITY_BELOW_NORMAL is -1
(decrease parallel port’s priority).