MacTwister: a MacCon/Etherport/Dayna Twisted Pair breakout board

[Aeroform]

This great little piece of kit made my way thanks to @moldy.

Firstly tested it out on my SE/30 combined with a Kinetics Etherport II SE/30. It was a simple plug and play and happily chugged along peaking at 120kB/sec. Not bad reaching almost a megabit on 34 year old gear! (Running OT on 7.5.5)

Then it went into a Macintosh SE equipped with a “Etherport SE”, after some major software hurdles not to blame on the MacTwister I finally got it up an running without a hitch. Here the speed was a blistering 15kB/sec running MacTCP on 7.1.

Some extra reflections:
- Tested on two different routers that usually struggles with auto negation. For some reason both happily set their port speed to 10/half automatically 100% of the time. Don’t know if that’s due to the mactwister or simply the Etherport cards doing a good job with that.
- Build quality / soldering is Excellent and it looks stunning, fits well and is a breeze to use.
- TX/RX leds eased troubleshooting
- Can highly recommend!

 

[LaPorta]

What is a piece of kit?

 

[Aeroform]

What is a piece of kit?

“piece of kit​

A specific item, often a piece of equipment. Primarily heard in UK.”

Sorry as a Swede (that has had obligatory british english as part of the curriculum) I don’t always realize some expressions doesn’t make sense in US english

 

[LaPorta]

“piece of kit​

A specific item, often a piece of equipment. Primarily heard in UK.”

Sorry as a Swede (that has had obligatory british english as part of the curriculum) I don’t always realize some expressions doesn’t make sense in US english

Oh that’s ok! It at least sounded roughly like “piece of s*it” in American English, so I wanted to make sure I had it right! These little things look like they are a great help, I may order one for my MacCON SE.

 

[JackRubin]

Hello,

I would like to share my project that is long overdue for publishing here - MacTwister, a fairly universal Twisted Pair breakout board for a variety of SE and SE/30 network cards. It’s about the small PCB that you screw to the computer chassis that contains an external connector.

I was motivated to complete this design as I had one “widowed” MacCon without a connector board and my other MacCon and Etherport only had coax+AUI connectors and would require a not so nice external converter.

Here comes MacTwister:
View attachment 60691
View attachment 60692

So what’s the deal? First of all, the idea is to support two typical connection pinouts for the common network cards:

• Asante MacCon (both SE and SE/30 tested)
• Shiva/Kinetics EtherportSE (tested) and Dayna (not tested, but it seems it has the same pinout)

The card can work with both network cards without any modifications, you just need to plug the 16pin IDC cable into the correct socket. This card is not a network card, it requires one of the above mentioned cards to be present.

But "there is one more thing". Because of the short supply of AUI↔Twisted Pair transceivers, the card was designed to support all three common options from the era:

• T7220 (and T7220A which is backwards compatible)
• AM79C98 (DIP case)
• LXT902PC (PLCC case)

I managed to find all three types on ebay/aliexpress and test them. Below you can see 3 cards with different transceivers, all working without electrical changes (minus the three jumpers that need to be bridged for LED indicators to work with AM79C98).
View attachment 60690

My SE and SE/30 are happily running with the breakout board!
View attachment 60693

You can find more details about the project here: https://dymczyk.com/mactwister-maccondaynaetherport-rj45-breakout

Finally, action items:
1. I'm looking for 2-3 early testers of the card - I could supply the newest version and I would be happy to get feedback, particularly a heads-up if it works. Please let me know in PM if you would be up for it!
2. I have a few (around 10) spare cards of the newest revision which are mostly populated, but I would need to order a few components to finish them. Please drop me a message or post here if you would be interested in the card at about $35/CHF35 + shipping. I can then post in the Trading forum with the details, but I would like to gauge the interest.

 

[JackRubin]

Hi,

Very nice! I'd like to obtain one of these adapters if possible.
Thanks.

 

[cheesestraws]

“piece of kit​

A specific item, often a piece of equipment. Primarily heard in UK.”

Oh that’s ok! It at least sounded roughly like “piece of s*it” in American English, so I wanted to make sure I had it right! These little things look like they are a great help, I may order one for my MacCON SE.

This expression seems to travel particularly badly - I'm sure I had to explain it to someone about AirTalk too!

 

[HAL2001]

Is it possible for me to get one! I have a Asante card but without the bracket.

 

[moldy]

Is it possible for me to get one! I have a Asante card but without the bracket.

@HAL2001 I'll contact you via PM, I think I should still have a few cards available

 

[mg.man]

@mg.man it looks very much like it could be compatible - the big IC in the DIP48 package is likely DP8390, the same as on the Kinetics I tested MacTwister with. (and also MacCon uses the same family)

Oh my!... I totally lost track of this - sorry! If you could keep an earmark on one I will buzz out my connections. Will happily cover postage, etc. if it looks like it'll work.

 

[mg.man]

Any chance you could check how AM7992B is wired to the 16pin connector? (I assume it's J1)

This is the pinout of AM7992B:

On the MacTwister side, I have the following pinout for Kinetics:

• Pins 1, 2, 3, 4, 6 are power
• 5, 9, 10, 13, 14 are GND
• 15, 16 - Collision
• 7, 8 - Data out (so Transmit I guess)
• 11, 12 - Data in (so Receive)

Please let me know, it would be awesome to get another card running with MacTwister

OK, so, o n l y 2 months later... I finally managed to clear some space and probe out the connections.

Here's how my card maps out :

• Pins 1, 2, 3, 4, 6 are power -- confimed
• 5, 9, 10, 13, 14 are GND -- confirmed
• 15 -- connects to AM7992B, pin 24, Collision+
• 16 -- connects to AM7992B, pin 23, Collision-
• 7 -- connects to AM7992B, pin 14, Transmit+
• 8 -- connects to AM7992B, pin 13, Transmit-
• 11 -- connects to AM7992B, pin 22, Receive+
• 12 -- connects to AM7992B, pin 21, Receive-

I think that means my card uses the same Kinetics pinout, = a MacTwister should work for my card as well!?