A2060 Reference

The A2060 is a full-length Zorro-II network card that supports the Arcnet standard. While Ethernet is far more popular, Arcnet has recently become very cheap on the Amiga due to a surplus of these cards.

While Arcnet does not transfer information as quickly as Ethernet, tests of actual transfers on the Amiga suggest that it can move information at rates up to 150K bytes per second, which is adequate for many purposes. Arcnet can be configured in a bus arrangement where each machine is linked to the next, or in a star, where all the machines are connected to an active hub. The A2060 will work with both setups.

The A2060 has some bugs. First, the "hybrid" chip that forms the electronic interface to the Arcnet network comes in two different versions: HCY 9058 (for bus networks) and HCY 9068 (for star networks). As the A2060 manual describes it, the board is for a bus network, but many A2060s come with the 9068 (star) hybrid installed. A bus network needs 93-ohm terminators at each end, and this works fine with the 9058 (bus) version of the hybrid. With the 9068, however, the hybrid itself performs the termination. To connect two machines with 9068 hybrids, run coax from one machine to the other, without using terminators. Using T-connectors to attach more machines in the middle of the bus may or may not work, due to each one adding its termination to the bus. To connect a 9068-version A2060 to a bus network of 9058-version A2060s, place it at the end of the chain and connect the cable directly, without a terminator (this may limit the network to only being operational when the 9068-equipped machine is on). Both versions of the card should have no problems when attached directly to an active hub. It is also possible to replace the HCY 9068 hybrid with the 9058 version, provided you can locate one.

There are also several well-known problems with version 37.2 of the "a2060.device" driver software. Replacements for this driver are available in the comm/net directory of Aminet. Some commercial networking packages like Envoy 2.0 also include much better replacement drivers.

Other Notes

Arcnet requires RG62 coaxial cable, not the RG58 that Ethernet uses, and has a minimum cable length between stations of three feet (0.9 meter). Active hubs used for a star layout are self-terminating, so cables are connected directly between the hub and the Arcnet cards.

If the A2060 does not perform reliably even with updated driver software, check the board for cold solder joints on hand-soldered components like the BNC coax connector and DIP switches. Some or all of these components may need to have overly-long leads trimmed to prevent interference with adjacent cards or connectors.

Finally, the Arcnet address switches on the back of the board are labelled incorrectly in the manual (or on the board, depending on how you look at it). At least some A2060's have a sticker stuck onto the DIP switch, which may disagree with both other references. Ignore all of these: the correct layout is described in the Switches section below. (Assign Arcnet ID numbers starting with 254 and decreasing from there. This will provide a slight performance increase due to Arcnet's token-passing setup.)

Despite all the problems, the A2060 works quite well once the bugs are corrected.

Board Layout

 |        _________                 ...                            |___
 |       |   ROM   |                LED                            |
 |       |_________|                                 ______        |
 |                                                  |      |       |
 |                                                  |      |   Bit0#
 |                                                  |Hybrid|    .  # Arcnet
 |                                                  |      |    .  # Node ID
 |                       (Hybrid version number is  |      |    .  # Switches
 |                        labelled on the back side |      |   Bit7#
 |                        of the potted "chip.")    |______|       |_
 |                                                                 |_| BNC
 |                                                                 |
     |||||||||||||||||||||||||||                                   |


    LED: Access LED. Attach a hard disk access LED here to see activity on
         the Arcnet bus. The left pin of the connector is positive, and the
         board provides a current-limiting resistor.


    Arcnet Node ID: This switch is used to set the Arcnet address of the
      board (refer to the board diagram above). Bit 0 is the switch farthest
      from the BNC connector; bit 7 is the closest to the BNC connector.

    Switch settings:

      1: Down (toward the solder side of the board)
      0: Up   (toward the component side of the board)

    Note: Zero is reserved, and not a valid Arcnet address.

  Example Arcnet Node Address Settings

     ID     Binary   Bit7  Bit6  Bit5  Bit4  Bit3  Bit2  Bit1  Bit0
    -----  --------  ----  ----  ----  ----  ----  ----  ----  ----
     254   11111110  down  down  down  down  down  down  down   up

     253   11111101  down  down  down  down  down  down   up   down

     252   11111100  down  down  down  down  down  down   up    up

     128   10000000  down   up    up    up    up    up    up    up

       3   00000011   up    up    up    up    up    up   down  down

       2   00000010   up    up    up    up    up    up   down   up

       1   00000001   up    up    up    up    up    up    up   down