from my recall, the plan I had for 270 was a mirror image of the final design so 180 would be the only one needing a stack.

I was feeling pretty good about the trace layout on the last upload. I was wanting to add ground layers though but it was proposed it would cost too much for that many layers.

I made it in a way that was symetric so that it didn't need to be keyed, my idea for ground was for a spring to be soldered on a central pad that contacted the cpu chip gold cover or an external ground lead.

Mapping out vss and tying /bonding it to the proposed gnd floods and keying(marking)pin one would be possible, though I don't believe the result would be better. it would just ruin the universality of it. though admittingly the universality doesn't have much benefit, wrong insertion is still possible if new pin one location isn't minded.

as for using thru hole for this, maybe someone can figure that out but when I looked at it it looked like asking for a absolute rat's nest. using floods would be the first change in a design like that. the layer count would likely be more than the sxl2 as on the sxl2 many traces didn't have very far to go where as on this they would all have to go far and jump over one another. the thru hole would make space even more limited.

not saying impossible, my 2 cents is try what I made with gnd floods, and see if that works. for 270, just invert the 90 (in software).

When you pull out VCC and GND to their individual planes, you will have less traces to route, saving some PCB real-estate. 180-deg is the most important rotation based on what I've seen in my giant stack of 386 motherboards. I'd suggest to Batyra that they start with this orientation. I have no doubt that the original proposal can be accomplished with 8 layers, individualised PCB's for the orientations, and using through-hole for at least one of the sides (ideally the pin side). A small increase in the PCB foot-print is an acceptable trade-off for using through-holes.

I'm looking forward to seeing what Batyra and his accomplice come up with here.

Batyra, what is your target CPU for the Panda 386V?