The printer MUST support basic PCL. I actually have several of the old 2934 character printers with parallel interface happily connected to JetDirect boxes and spooled using the network print spooler. Works fine. As a test, I even hooked up an ancient HP ThinkJet to a JetDirect box and spooled it off my system.

I've also been able to use non-HP, but PCL-compatible, laser printers.

As for the network interface card/box, ideally it should be either a JetDirect or 100%-compatible. However, by using the undocumented option "snmp_enabled=false" in npconfig.pub.sys, you should be able to use non-JetDirect cards/boxes. I've successfully used Intel NetExport boxes for example.

On an Intel NetExport box with 3 ports (2 parallel and 1 serial - HP does not make a JetDirect with a serial interface) you use the tcp_port_number directive in NPCONFIG.PUB.SYS as follows:

Serial: tcp_port_number=2501

Parallel 1: tcp_port_number=3001

Parallel 2: tcp_port_number=3002