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DuoNet: Ethernet for the Macintosh Duo Expansion Connector


Well-known member
Project status: I found the connector for the Duo expansion connector, and now I'm building the infra to make a Duo->Ethernet module, like the Asante NetDock
The above project status will be edited as the project is completed

I have a few Duo systems, including a 2300c and a 280c, as well as a few interesting docks including the Newer SCSI microdock and an Asante Micro EN/SC, an Asante NetDock, and a Newer Ultradock 16SCE. My biggest problem is that I have no easy, compact solution for Duo to Ethernet capability. As I discussed before, the Asante NetDock doesn't work with anything other than a 68030, meaning my 2300 and 280 simply don't have portable Ethernet. I want a small Microdock with Ethernet that works, which probably means I'll have to build one. So now I'm starting the DuoNet project.

Project Beginnings: I started this project by sourcing the connector mentioned in the Macintosh Duo System Developer Note, the JX20-152BA-D1LT-H. I found a similar connector (a JX20-152BA-D1LT-HA) on an online component reseller. While not an exact part number match, it seems to fit:


The cost of this connector is considerable at about $80 USD/piece. This means the DuoNet will never be a manufactured product or a kit; the cost of components means this will be either a one-off or extremely small batch. I will however, open up all the files for you to build your own.

Project Plan: Right now I have a few PCBs on order to make sure I have the footprint of the connector correct. Thanks to some 90s engineer labeling the pin numbers on the floppy minidock PCB, I should have the footprint and schematic correct; I plan on testing this immediately.

Concerning the design of the DuoNet, I believe the simplest path forward would be to create something like a Duo Expansion Connector -> SCSI -> Ethernet solution. Going from the connector to SCSI is straightforward, from the documentation, requires a 53C80 SCSI controller, a chip that's still available at mouser and digikey. From the SCSI, I can attach something like the Scuznet to give me Ethernet, That's not to say this is a completely no-code solution to giving Ethernet to a duo; I'll still need to write a declaration ROM in the adapter. Careful inspection and some light reverse engineering of the microdocks I have, along with the documentation, will help with that.

Plan TL;DR: mash up a scsi chip with Scuznet.

Want anything else: While the actual physical space this circuit will take up might be too much for the standard microdock format, I'm wondering what other additions duo enthusiasts would want. The expansion connector offers a direct connection to the battery + connector - meaning a PB500-style dual-battery system is possible, as would an immense battery pack built around the bottom of a Duo. If I already have SCSI, I could add a normal 25-pin connector, or I could just throw a raspberry Pi in there, because that's what all the cool kids are doing.



Well-known member
The cost of this connector is considerable at about $80 USD/piece
Ouch! And I thought the near-unobtainium '040 PDS connector was expensive... can you share picture of the connector on its own? I wonder if there some possible substitute...
Concerning the design of the DuoNet, I believe the simplest path forward would be to create something like a Duo Expansion Connector -> SCSI -> Ethernet solution.
As far as I can tell from the dev note you linked, the connector is basically the signalling from a '030 PDS plus some extra signals to support more functions (floppy, ...).
Going through the 53c80 you mentioned would basically be "build a PDS SCSI device", an interesting project but it might not offer good performance - I have of the those SCSI/Ethernet adapter from way back in the day, they aren't fast.

Theoretically, I think you could adapt any existing PDS -> Ethernet adapter into a Dock -> Ethernet adapter. It might be a more efficient solution. It might be a simple matter of routing the signals properly between your connector and the PDS DIN 41621 connector (96 or 120 pins).

Alternatively, it should be possible to build a 'new' device using a more modern Ethernet device (looking into it for the NuBusFPGA first), but the issue if going to be the software. There's an example of driver for the Etherlink/NB available in addition to Apple's documentation, but it's still a lot of work.