Project30 - fourth edition - Radius IIsi NuBus Adapter build for SE/30?

[Trash80toHP_Mini]

I would recommend first doing a prototype without too much worry about fitting in a case, just to make sure the interface can be made to work (and potentially expanded to more than one slot).

Would that I could. My prototyping was done in the days of wire wrap when I could screen print enamel resist a/o cut vinyl on my plotter for simple one or two offs.

Don't have access to a Radius NuBus Adapter. As far as I know only @Bolle and @joethezombie have them. I took one look at the mass of birdseed on the backside of the Apple adapter and gave up all hope of looking into that thing.

For cost reason, you really want all your SMD components on one side if someone like JLCPCB is to assemble them.

The only homebrew board I have from an SE/30 batch so that's my frame of reference. Solder side would have birdseed and whatnot along with the buffers. Topside soldering of the transceivers would be done along with the thruhole components.

Beware of the data order from PDS to NuBus; first NuBus is multiplexed so all 8 drivers are going to NuBus A/D signals while half of them will go to the PDS D ,and half to the PDS A. And the byte order for D is reversed as NuBus is little endian. And having done some tests at one point, IIRC, the byte/bit order is the opposite between NuBus and PDS... The routing is not simple.

So far beyond my ken at this point, maybe after retirement for anything even close to this kind of exercise.

I'm just playing at arranging the building blocks to see if it could be done at all. If it can't be done in four layers it'd be a non-starter, no? Hoping someone competent might take a whack at this, but as it's not for the SE/30 crowd, it'll likely never happen.

As a knuckle dragging, Neanderthaler level hacker, I don't really need this adapter for my SuperIIsi™ NuBus+PDS build. It's going in exactly the opposite direction as soooo planned loooong ago!

 

[nickpunt]

iirc we know some nubus cards aren't too strict about nubus timing from prior tests by @joethezombie with the radius, which makes me think a very mild overclock of the SE30 (~18mhz?) might produce some balanced state where both nubus cards and the se/30's features like sound/floppy work by not pushing either too far outside their limits. Obviously bigger SE30 overclocks produce problems but here the goal is a very minor bump (16 -> 18mhz), something so worthless people have probably not seen the point of or tried before.

 

[Bolle]

Unfortunately, it seems the only available schematics for the Macintosh II (from bomarc) are for the later version using the NuChip.

That should be everything that's involved with Nubus (minus the actual slots and signal termination but that's obvious)

 

[Melkhior]

That should be everything that's involved with Nubus (minus the actual slots and signal termination but that's obvious)

Hehe, seems you're already working on it

Fragment of schematics like this might help understand, but are too limited for recreation by a third-party like myself. For instance, take U28. It has an OE signal that doesn't appear anywhere else (that I can see), so is that driven externally or always-on? And it has an output called "/RMC", is that something local or is that related to the MC68020/MC68030 "/RMC" signal? If it is (seems likely), then it can't be always driven as that would interfere with the CPU behavior so where does that OE signal come from? There's also a "/RMC.SYNC" in that fragment, but that could be local. Others GAL raise the same question as they also have seemingly unconnected OE.

 

[Trash80toHP_Mini]

When thinking about the 16MHz MacII.HAL setup for the SE/30 PDS when the notion first came up I was worried it wouldn't work in the IIsi. Wondering about that now, might it work off C16M rather than CPUCLOCK in the IIsi? If so, three headers and a jumper or a two way switch might be in order?

 

[Trash80toHP_Mini]

We've taken a (forward) step back into Rev4 of this insanity, wondering if info in Rev5 might help here?
Project30 - IIsi NuBus Adapter in SE/30 - fifth edition

A lot of info regarding 020/030 NuBus implementations developed in there. MacII.HAL is 68020 and 030 PDS is 68030, so we have to take that into account again here.