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.
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
| _________ ... |___
| | 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.
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
Converted on 02 Jun 1997 with RexxDoesAmigaGuide2HTML 2.1 by Michael Ranner.