Notes on the Xircom PE3 parallel port Ethernet adapter

Description

The Xircom PE3 series adapters are Ethernet adapters from the early 1990s designed for notebook computers that needed Ethernet but did not have any internal expansion slots. They worked by using the the parallel port as an expansion bus, which is not as fast as having a real Ethernet adapter on a card but it is fast enough for most uses. While designed for notebook computers they will work on any machine with a parallel port, which is great for machines that have limited (or no) expansion slots available. It also makes it useful for machines where you want an Ethernet connection but you don't want to go through the hassle of opening the case and installing a card.

There are three models in the PE3 series:

• Xircom PE3-10B2 - Thin Ethernet (IEEE 802.3 10BASE-2 with BNC connector)
• Xircom PE3-10BT - Twisted Pair (IEEE 802.3 10BASE-T with RJ45 connector)
• Xircom PE3-10BC - Combination (both Twisted Pair and Thin Ethernet)

(Images taken from the Xircom Pocket Ethernet Adapter 3 User's Guide)

From a software point of view they all look the same. The only difference is in how they connect to your Ethernet. Most people will prefer the 10BT or 10BC versions as they connect easily to a modern home network using a CAT 5 patch cable. The 10B2 or the 10BC version using Thin Ethernet can use an older style of Ethernet called "ThinNet" which some older hubs support, but it is not as common anymore.

The included software supported Novell NetWare (ODI), Artisoft LANtastic/AI 4.1, DECnet-DOS, DEC PCSA and PATHWORKS, NDIS, ODI, AT&T StarLAN 10, and the DOS packet driver specification. (I discuss the DOS packet driver parameters on this page - for the others you have to refer to the user manual.)  The software can be found here: http://downloadcenter.intel.com/Detail_Desc.aspx?ProductID=756&DwnldID=3172&lang=eng&iid=dc_rss

Within the device was an Ethernet chipset and a 32KB buffer area. 32KB was generous for the time and helped make up for the slowness of the parallel port by providing extra buffering. Speed is limited to 10Mb/sec which was the fastest speed at the time, but it works well in mixed 10/100 Ethernet LANs.

Connecting: Parallel ports and Power

The parallel port does not provide enough power to operate the device so an additional source of power is needed. There were two methods for powering the device:

• Use a "wall wart" transformer that provided 12VDC output
• Use a "Phantom AC Power Cable" that borrowed power from the PS/2 keyboard port and fed it to the Xircom. Your normal keyboard could still attach through the pass-through connector on the cable.

The choice of parallel port makes a difference on performance. A standard parallel port like the kind found on the original IBM PC, XT, PCjr, and AT is capable of sending a byte of data out of the port at a time, but is only capable of reading 5 bits at a time. This is due to the original design of the parallel port which was supposed to support a printer, not general purpose I/O devices. The design shows up in the performance of the Xircom - on a slower machine you will find that the Xircom can send data twice as fast as it can read it. Later parallel ports improved by allowing the parallel port to read a full byte at a time, thus making reading from attached device the same speed as writing. And even later parallel ports introduced an "EPP" (Enhanced Parallel Port) mode which make the handshaking between the parallel port and the device more efficient, boosting the transfer rate.

The Xircom can support any parallel port, but at a minimum you  should try to use a bi-directional parallel port. Standard ports work, but they are half as slow when receiving data as compared to sending data.

The Xircom does not provide a pass-thru for a printer or other parallel port device. I recommend plugging it directly into the parallel port, and not in a daisy chain behind other devices like a Zip drive, SCSI adapter, or any other parallel port device with a pass-thru connection.

Do not connect the Xircom to a parallel port while the computer is turned on. Parallel ports are not designed for that and you can damage them if you add and remove devices while the power is on.

Packet driver usage

All of the drivers for this adapter can be found at Intel's support site:  http://downloadcenter.intel.com/Detail_Desc.aspx?ProductID=756&DwnldID=3172&lang=eng&iid=dc_rss

The packet driver for this adapter is called PE3PD.COM. According to the documention it is supposed to be able to find the Xircom adapter and configure itself automatically. Below is a list of command line parameters:

Polling mode (INT=0)

Parallel ports have hardware interrupt wiring but often they are not enabled. Most DOS software using the parallel port writes to the port; if a read needs to be done polling is usually faster. Not using the parallel port hardware interrupt also allows you to use multiple parallel ports at the same time without having to worry about which one needs to be serviced when the shared interrupt line goes off. (If each port had its own hardware interrupt line there would be no problem, but interrupt lines are limited in number so that is unusual.)

An Ethernet adapter on a parallel port presents an interesting challenge - one can not predict when a packet is going to arrive. Instead of actively polling the port looking for data from the Ethernet adapter a hardware interrupt would be preferred.

Sample command lines:

Diagnostic Lights

All variants of the PE3 have two diagnostic lights on them. The meaning of the lights can be found in the table below:

Note: The PE3-10BC has a different power on indicator than the others do. Look for the triangle above the letter "i" in the Xircom logo to turn red when the power is on.

The power indicator only lights when power is applied to the Xircom, the Xircom is attached to a parallel port, and the computer is turned on.

Utility programs

Besides the packet driver there are two utility programs you should know about:

• EPP.COM (Enhanced Parallel Port Utility): Use this utility to enable EPP mode on an EPP capable parallel port.
• PE3TEST.EXE (Diagnostic Utility): Use this utility to test your Pocket Ethernet adapter. (You can not run this if the packet driver is loaded.) The utility will give you information about your adapter, test the components, do a transmit test, and report on traffic that it senses on your network.

Machines known to work

Probably any machine you can find with a parallel port will work. I have tested the following machines:

• IBM PCjr with the standard parallel port sidecar, bi-directional parallel port sidecar, and LPT2 parallel port sidecar
• IBM PC 5150 and IBM PC XT 5160 with various parallel ports. (You may need to use the NON parameter to force standard mode on the parallel port included on the IBM Monochrome Display Adapter.)
• IBM PC 5140 Convertible
• IBM PC AT 5170
• IBM PS/2 Model 25
• IBM PS/2 L40SX laptop
• Generic 80386-40 system with standard parallel port

In addition to these machines, here are some more that others have reported work:

• Data General One Model/2 (thanks Carlsson!)
• Commodore C286-LT portable (thanks again Carlsson!)

There is at least one machine that does not work - the Olivette Prodest PC-1.  Apparently it has a slightly non-standard parallel port.

The Xircom manual does not specify a required version of DOS. Given the nature of the packet driver and the lack of dependencies on DOS features just about any version of DOS should work. I have used everything from DOS 2.1 upwards.

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Created January 31st, 2011, last updated March 3rd, 2013
(C)opyright Michael B. Brutman, mbbrutman at gmail.com