NuBus Bus Length Limitations

[CelGen]

One of the guts I own from an old Avid Media Processor is a two slot NuBus expansion. It clipped onto the main logic board with a passive bridge board.

My Quadra 950 needs one more slot to hold a Digidesign input card and I want to route using ribbon cables one of the slots out of the case and into a shoebox with the expansion to hold the card and the DSP card which originally was in the slot.

Is there anything I should know before I make up a set of ribbon cable adapter PCB's? The distance between the system and the shoebox will be no more than 3 to 4 feet.

 

[resx]

I can't speak for the electrical eccentricities of NuBus, but I have found that PCI Express does not like long (unshielded) ribbon cables. Anything over approximately 8 inches tended to cause issues for me.

I do see that this exists: viewtopic.php?f=16&t=14915

However, I don't see any sort of cable length. A shielded ribbon cable might be necessary.

 

[Trash80toHP_Mini]

I'm not sure about your description. You have the expansion box and "passive" adapter card, but not the cable?

cable driver ICs / line drivers would probably be necessary for anything longer than a very few inches. You'd probably get more length than the PCI cables available on eBay, but not all that much. It sounds like they may be implemented on the expansion box LoBo.

What connectors are involved on each end and what's the spacing of the contacts?

Alternate ground lines and shielding between multiple cables sounds like the bare minimum in terms of an extension.

Fabbing adapters for using the standard alternate ground line IDE ribbon cables might work nicely.

 

[CelGen]

My bad. Here:

(also, my fault. That's more than a two slot expansion)

Anyways, there's no physical space in the 950 to fit the exapnsion board using that little bridge board. Instead I want to replace it with a ribbon cable with a NuBus connector on either end.

 

[olePigeon]

Will that work with any NuBUS device, or just AVID cards with special AVID software that knows to look for them?

 

[Trash80toHP_Mini]

EEK! 8-o That looks like a worst case scenario for your hack unless AVID used that same LoBo with adapter cards for a box on the end of a cable and all the necessary line boost is built into your LoBo. However, it makes way more sense for them to have put the cable drivers on the two adapter cards.

That setup looks like it's an add-on for use with a second board (not necessarily identical at that) to fill an 8 Slot Expansion Box. :-/

Does that jumper board (analogous to the HPV adapter cables for NuBus G3 accelerators) even have enough center to center offset to give you room to use it with the end slot of the 950 MoBo?

Doesn't look it, that'd be a very bad sign if so. If that's a Metric CrapLoad of SMT termination for Slot 8, that could be an even worse scenario for your plans. Worse than that, if the keying of the EuroDIN connectors is the reverse of the 950 . . .

 

[Unknown_K]

I think AVID had a special built 8100 Nubus system with that adapter in a special case.

 

[Trash80toHP_Mini]

That makes a LOT of sense, I was thinking a custom rackmount Mac if the connectors align properly.

 

[CelGen]

I think AVID had a special built 8100 Nubus system with that adapter in a special case.

I saw it. I pulled it out the trash. I took the bezel. I took the expansion board. I was a retard. I didn't even think that perhaps one day I would be building an editing rig and it might of been worthwhile to hold onto that massive system considering you require a lot of cards.

 

[James1095]

PCI Express is a serial interface clocked at something like 2.5 GHz. I haven't tried, but I would expect NuBus to be far more forgiving as it runs at what, 16 MHz? That's orders of magnitude slower. You might have good luck using cabling similar to SCSI to extend the bus.