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Hardware: A2060
(Article written by Markus Illenseer and excerpt from comp.sys.amiga.reviews - February 1994)


Brief description

The A2060 Arcnet Card is a true network device for the Commodore Amiga. It has become cheap lately and thus is a good alternative to other network devices.

Author/company information

Name: Commodore Business Machines
Address: 1200 Wilson Drive, West Chester, PA 19380, USA

[Varies for other countries]

Distribution

The card is available from every good Amiga dealer and mail order company. However, the card is no longer produced, and thus the second-hand market is open to all prices.

List price

Suggested retail price is DM 126.- or about $70 (US).
Street price is about DM 90.- or about $52 (US).

Special requirements

Hardware

Amiga with Zorro-II or Zorro-III slots: A2000, A3000, or A4000.

Does not work with A500, A600, A1200.

At least 512KB of RAM.

Software

Requires networking software such as:

AS225R1 TCP/IP clients;
Envoy network file system and network protocol;
Enlan DFS
Oxxi Novell Client
AmiTCP TCP/IP

and the SANA-II device.

Machines used for testing

Amiga 2000
Tested with 1 and 2 MB Chip RAM.
4 MB of 16-bit RAM
A2630 accelerator board (4 MB of 32Bit RAM) (The accelerator board is of course not required.)
A2091 SCSI adapter with several hard drives
AmigaDOS 2.04 and Kickstart 37.175.

Amiga 3000, 2 MB Chip RAM, 8 MB Fast RAM, and several hard drives.
AmigaDOS 2.04 and Kickstart 37.175.

For some further tests, a A2065 Ethernet card was used.

Review

In a general overview, I shall describe the card and the required software to connect Amiga machines. I then will review the installation and the functionality of the card and the software.

General overview

Arcnet is a basic hardware protocol for information exchange between computers. Onced connected, these computers represent a Local Area Network (LAN) and allows a group of people to share resources through the network on other machines at other locations. The main computer in the network is commonly known as the "file server," and the other computers are known as "clients."

The Arcnet networking system is very old, introduced in the early 1980's, and was popular in the days of IBM XT compatible machines. As XT machines had an 8-bit bus subsystem, and the Arcnet Interface was not the fastest available, and was soon replaced by the faster ethernet protocol.

Still, Arcnet is cheap and reliable, which makes it useful for small LANs and simple network sharing. Of course, it has been improved upon in both speed and functionality.

The manual claims that Arcnet is able to support up to 256 nodes (machines) and that the speed is about 2.5 Mbps (megabits per second). Let's see what we really get.

Required software

On top of the hardware protocol Arcnet, we need software to provide file sharing or other kinds of network services. Available for the Amiga are the following protocols:

Commodore AS220 R1 TCP/IP stack & clients (never made available :-)).
Commodore Envoy file system and network protocol (available now!).

Enlan DFS DEC-Net software.
Oxxi Novell Client software.
AmiTCP freely distributable TCP/IP stack for the Amiga.

The TCP/IP stack protocol is very common in most LANs, and is also used in the Internet. It does provide clients to transfer files to and from a remote machine or server (ftp, rcp, nfs), run programs on a remote machine (rsh, telnet, rlogin). It also provides servers (daemons) to make files available for other machines (ftpd, nfsd) or to allow other people in the LAN to start programs on the Amiga (telnetd, rlogind).

TCP/IP allows you to connect computer platforms other than Amiga to your LAN; i.e., Unix platforms or even PC-based LANs (if they can be connected with Arcnet).

The Enlan DFS system allows you to connect your Amiga to a LAN with Digital Equipment DECstations running DECNet. Just one problem: DEC does not support Arcnet.

Oxxi provides a Novell Client for the Amiga and allows you to share the provided services of a Novell LAN (based on Arcnet).

AmiTCP currently is the only available TCP/IP stack protocol for the Amiga, as AS225 R1 from Commodore is no longer supported and AS225 R2 is still not available. AmiTCP is freely distributable and is available on the Aminet ftp sites. As full source code is provided, it is possible to program your own clients.

The Commodore Envoy system is available right now and is probably the best choice for Amiga-only LANs. Envoy can be purchased from Amiga dealers and mail order companies. A review of Envoy will probably follow soon.

Currently it is not possible to run AmiTCP and Envoy at the same time without problems (gating).

Between the bottom layer Arcnet hardware and the top layer software (TCP/IP, DECnet, Envoy), there is a middle layer which handles data transfer between the hardware and the software protocols. This aids hardware independence. On the Amiga, this layer has been defined by Commodore and is known as "SANA-II." This is the hardware-dependent layer and provides device drivers for the hardware which can be then accessed by the software layer.
Hardware: Arcnet     Ethernet    Serial    Parallel
               \         |       /          /
Interchange:       SANA-II Interface
               /         |       \
Software: TCP/IP     Dec-Net     Envoy

The SANA-II software -- that is, device drivers -- is freely distributable and can be found on Aminet or Fish Disk 779 (and possibly later Fish Disks).

For the A2060 Arcnet Card, we need the A2060.device.

Installation

The A2060 card comes in a box together with a 2-meter long, shielded, coaxial cable, a BNC-T connector, one Terminator Cap and a small (English) manual.

The card is a full-length card for the A2000 which also fits easily into the A3000 and A4000. The installation is very easy but should be done by a qualified technician if you have two left thumbs.

[MODERATOR'S NOTE: If you are not comfortable opening up your Amiga, then you should have the work done by an authorized Amiga service center. Opening your Amiga yourself may void your warranty, and careless work may even damage the machine. - Dan]

The manual explains in detail the installation of the card into an A2000, but the explanation can be adapted for the A3000 and A4000.

Now we come to the step where we connect the machines.

Bug!

The manual explains that the A2060 ARCnet uses a bus network layout. Unfortunately, this is only partially correct, because most of the new A2060 cards (produced in the years 1992 and 1993) have a hybrid chip (the part on the card which is responsible for the communication on the cable) which allows only a star network configuration.

We made lot of tests before we detected this bug. It is impossible to connect more than 4 cards in a star network, and thus the claimed 256 nodes in the bus can never be achieved without any prevention. You either need to have active hubs and passive hubs (some sort of expansion or repeater in the bus) or need to exchange the faulty hybrid chip. The latter is by far cheaper.

The hybrid chip which is able to drive the bus network is named HCY 9058, and the star network hybrid HCY 9068.

Tests showed that once this patch is done, it is possible to connect more than 8 Amigas without any problems. If you don't have more than 4 machines to connect, don't bother about this problem.

You can circumvent the problem using gateways; i.e., an ethernet backbone or a machine with 2 ARCnet-cards.

Another bug!

The manual has a funny bug, which is really nasty - probably it is not the manual but an error in the typesetting. The explanation of the DIP-switch is reversed by 180 degrees. This means that the DIP-switch '1' in position 'ON' enables not the address '1', but the address '127'. And all DIP-switches moved to the position 'ON' will yield '0' but not '255'. And '0' is not supported.

Work

After the (tricky) installation part, we come to the first tests. Running Envoy, we can export all or part of a hard drive (or any other device) to the network. Doing a simple 'DiskSpeed' allows us to test the speed of the card. You will see that the Arcnet is a bottleneck, it is not as slow as you might think. Here are the test results:

======================== RESULTS BEGIN HERE ==============================
Comment: b-alfa: is remote hard-drive.

MKSoft DiskSpeed 4.2  Copyright ) 1989-92 MKSoft Development
------------------------------------------------------------
CPU: 68030  AmigaOS Version: 37.175  Normal Video DMA
Device: b-alfa:    Buffers: <information unavailable>
Comments: DiskSpeed 4.2

CPU Speed Rating: 1371

Testing directory manipulation speed.
File Create:            6 files/sec  |  CPU Available: 83%
File Open:             12 files/sec  |  CPU Available: 72%
Directory Scan:        69 files/sec  |  CPU Available: 75%
File Delete:           19 files/sec  |  CPU Available: 77%

Seek/Read:             15 seeks/sec  |  CPU Available: 68%

Testing with a 512 byte, MEMF_FAST, LONG-aligned buffer.
Create file:        11352 bytes/sec  |  CPU Available: 75%
Write to file:      12064 bytes/sec  |  CPU Available: 74%
Read from file:     16979 bytes/sec  |  CPU Available: 65%

Testing with a 262144 byte, MEMF_FAST, LONG-aligned buffer.
Create file:         8589 bytes/sec  |  CPU Available: 87%
Write to file:      10187 bytes/sec  |  CPU Available: 85%
Read from file:     74017 bytes/sec  |  CPU Available: 46%

Average CPU Available: 62%  |  CPU Availability index: 850



Comment: b-ram: is remote ram disk.

Device: b-ram:    Buffers: <information unavailable>

CPU Speed Rating: 1371

Testing directory manipulation speed.
File Create:           15 files/sec  |  CPU Available: 66%
File Open:             16 files/sec  |  CPU Available: 64%
Directory Scan:       273 files/sec  |  CPU Available: 27%
File Delete:           37 files/sec  |  CPU Available: 61%

Seek/Read:             20 seeks/sec  |  CPU Available: 59%

Testing with a 512 byte, MEMF_FAST, LONG-aligned buffer.
Create file:        22744 bytes/sec  |  CPU Available: 53%
Write to file:      23525 bytes/sec  |  CPU Available: 52%
Read from file:     23991 bytes/sec  |  CPU Available: 52%

Testing with a 32768 byte, MEMF_FAST, LONG-aligned buffer.
Create file:        93102 bytes/sec  |  CPU Available: 24%
Write to file:     100012 bytes/sec  |  CPU Available: 20%
Read from file:     80988 bytes/sec  |  CPU Available: 41%

Testing with a 262144 byte, MEMF_FAST, LONG-aligned buffer.
Create file:         9346 bytes/sec  |  CPU Available: 86%
Write to file:       7454 bytes/sec  |  CPU Available: 88%
Read from file:     87255 bytes/sec  |  CPU Available: 38%

Average CPU Available: 46%  |  CPU Availability index: 631
======================== RESULTS END HERE ================================

Now where is the claimed 2.5Mbps? Remember that "bps" means "Bits per second"; thus, we have to divide 2500000 by 8 = 312500 Bytes/sec, makes about 300K/sec. The above best value is 100K/sec.

We have to consider that the 2.5Mbps are achieved only on the hardware layer of Arcnet. The software protocol has its own overhead, resulting in a loss of speed. This is about 10% of the real transferred amount of data.

Then we have to think about that the Arcnet Card is interrupt driven (polled I/O), and one interrupt on the Amiga yields into a busy system. To reduce traffic inside the Amiga, the driver uses the 4 buffers of the Arcnet hardware as a simple FIFO buffer. Unfortunately the 2060.device has some bugs in this buffer which yields lost packets and packet collision which will increase the traffic on the Arcnet bus.

You can see the mentioned problems in the last test, where a 200K file was used, which was transferred in the slow rate of 7K/sec.

Unfortunately, I was not able to connect my Amiga to an Arcnet-based PC-LAN, because I couldn't find one. Anyway, I don't see any reason why it would be impossible to connect Amiga-Arcnet to PC-Arcnet: the hardware protocol is the same, and if one uses TCP/IP as software layer it should be possible to interchange data.

Further tests were done using AmiTCP in a small LAN consisting of only Amiga platforms. The speed was exactly the same, which shows that the A2060.device is the bottleneck.

Also one machine was used as a gateway from Arcnet to Ethernet. Hence, it was possible for Arcnet-based machines to use resources of Ethernet-based machines. Using TCP/IP, it was even possible to connect the entire LAN to the Internet. This test was very successful, with just one minor problem: the gateway is very busy, and it is really recommended to have either a dedicated system or a fast machine for the gateway.

Small tests at an Amiga meeting showed that it is possible to connect the machines using long cables, not just the provided 2-meter cables.

Likes and dislikes

You get a good service for a cheap price, the reliability is high, and speed is quite good. I like the fact that you can easily connect several machines to the bus.

I dislike the bugs. The A2060.device is not the best although it is stable. Also the bus/star network 'bug' provided by the wrong kind of hybrid interfaces is somewhat nasty due to the impossibility to connect more than 4 machines.

Comparison to other similar products

There is no other Arcnet-Card for the Amiga available, thus we have to compare it with SLIP which is driven over the serial line (and is of course far slower), and with Ethernet (Commodore A2065 card) which is about 5 times faster.

Close to Arcnet comes a floppy port based system (e.g., Amoknet) which can also connect A500/A600 and A1200 computers. This kind of network is an Amiga-only network, and is reliable, but is somehow a system hog and uses almost all the resources of the Paula chip.

Compared to the evergreen ParNet (and the successor PNet or liana, both devices for SANA-II), Arcnet is by far more stable, because once one machine in a Parnet network crashed, the other had to reboot, too.

Conclusions

A reliable product which has some faults but is very usable and offers much for its low price. I'd rate it 4 out of 5 stars.

The last star can be achieved if a new A2060.device is available which fixes the buffer problem and offers better speed.


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