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Rare Cabletron Mac Nubus Network Adapter IIsi


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One of my first Macintosh computers I bought used in 1992 is this unusual Macintosh IIsi. I found it in a listing in a Want Ad and drove to the now defunct company that was selling it. He wanted $75, it included the infamous Nubus adapter with FPU and a Cabletron Network Adapter. Having no idea what all that meant, I had the money so I got it. Prior to owning this, the only other Macintosh I had used was a Macintosh SE which did have a 20 MB HDD. This IIsi was my main Mac until I got a G3 iMac DV in early 2003.
Some of the things I've noticed about this particular Mac IIsi was that it does not have the ROMs on the mother board. Instead, it has the Jumper on and a NON Apple ROM SIMM in the SIMM slot. Also, I noticed that with the Nubus Adapter and Cabletron network adapter installed when going to the "Startup Disk" control panel there was always a selectable option to boot off the the Network. There would be the Main HDD and also a Network option to boot from in the "Startup Disk" control panel. When the Nubus Adapter and Network card was absent there was no Network option in the "Startup Disk" control panel. Now I have 7 other Macintosh IIsi computers here ( most need recapping) and not one other can duplicate this. Selecting the Network option was pointless back then since I had no network of any kind. But selecting it would give a message stating that if there was no net boot volume available it would take longer to boot... or something to that effect.
This Mac IIsi needed a re cap long ago so it will not power up even with a known working PSU. The original PSU for this machine caught on fire after my first and last attempt at recapping something, some 12 years ago. (Didn't go well)
The Nubus adapter and Cabletron card are here still and in working order but I cannot duplicate this on any other Mac IIsi unless I insert the rare unknown ROM into another machine and bypass the MB ROMs with the jumper.
All I can think of is that it was a hardware developer company with a custom rom and an early net boot suite.
Can anyone shed some light on this and perhaps explain this? Has anyone ever seen anything like this before?


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and a NON Apple ROM SIMM in the SIMM slot

This will be where the netboot magic is living, by the sound of it, then. Can you dump the ROM for posterity? It'd be interesting to find out what's going on and see whether there are any messages in the code to say who made the ROM...


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I've never seen NetBoot on a 68k. That sounds cool and potentially insanely useful if somehow gotten to work. NetBoot on PPC OS X Macs was finicky.


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Afaik there is a netboot driver in the IIsi ROM from the factory but it’s disabled. Enabling it should be a relatively simple patch. I bet that’s what happened here.


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Afaik there is a netboot driver in the IIsi ROM from the factory but it’s disabled.

There is—but if that's true and someone was actually using it who wasn't Apple, that's doubly interesting, because no server software is known to exist (or, in public, as far as I know, ever have existed for that). Might make the software side less exciting, mind...