Parallel printer is slow

If your parallel printer prints abnormally slowly, verify that the configuration settings are correct. In particular, printing can be slow if the port is configured for the right I/O address, but the wrong interrupt vector. To check and change this setting, see ``Adding and configuring parallel ports''. To change the interrupt vector for a slow port, remove and reinstall the parallel port with the same I/O address but a different interrupt vector (5 or 7). Relink the kernel, reboot the system, and see if the port is still slow.

If the parallel ports are configured correctly and printing is still slow, your parallel port may not be capable of generating interrupts. In this case, you can try setting up polling for your printer port.

If your line printer is taking about four seconds per line, the printer may be deselecting itself after receiving each line of text and then reselecting. In this case, you can modify a kernel parameter to change this behavior.

Setting up polling

To speed up printing on your parallel printer, you can alter the way that the hardware and the printer driver communicate. The parallel printer driver can be made to ``poll'' a parallel port so that the driver does not rely on interrupts from the parallel port.

To set up polling for a parallel port or parallel printer, you must create a polling device file and reconfigure your printer to use it instead of the standard device. Use this procedure:

1. Bring the system into maintenance mode. See ``Using the shutdown command line''.

2. Note which parallel printer ports are configured. Enter:
   
   /etc/hwconfig -h

   You should see output like this:

   parallel 0x378-0x37A   07    -    unit=0
   

   where unit=0 refers to lp0.

3. Configure a special device file for the printer. Create a file called pa (if it does not already exist) in the /etc/conf/node.d directory containing one of the following lines:
   
   For lp0: pa lp0p c 64 bin bin 600
   For lp1: pa lp1p c 65 bin bin 600
   For lp2: pa lp2p c 66 bin bin 600

4. Enter these commands to reconfigure the kernel to recognize the new device:
   
   cd /etc/conf/cf.d
   touch /etc/.new_unix
   ../bin/idmkenv

5. At the prompt to rebuild the kernel environment, enter y.

6. Reboot your system. See ``Using the haltsys command''.

   When you enter multiuser mode, the new polling device is in place.

7. If you are using the print spooler, you must now inform the spooler of the new parallel poll device.

   In the Printer Manager, select Connection from the Settings menu. Do not select a standard parallel device name. Instead, select or enter either /dev/lp0p, /dev/lp1p, or /dev/lp2p.

Changing the MODE_SELECT kernel parameter

If you suspect that your printer is deselecting and reselecting itself after each line, change the value of the MODE_SELECT kernel parameter. (This works with both polled and standard lp devices.) The default value of MODE_SELECT is 1, which enables mode-select checking. To disable mode-select checking, set MODE_SELECT to 0. This removes the printing delay incurred by these checks.

To change the value of MODE_SELECT, use the Hardware/Kernel Manager as described in ``Configuring drivers with the Hardware/Kernel Manager''.

1. Select Tune Parameters from the Kernel menu.

2. Select 18 (Miscellaneous device drivers and hardware parameters).

3. Press <Enter> until you see MODE_SELECT, then enter 0.