Here's a snapshot:
The six-layer stackup is:
|1||Red||Top: SMD pads, simple routing|
|2||Hatched Red||Ground plane — not shown|
|3||Dotted Green||Unused, probably inter-board nets|
|14||Light blue||Mostly vertical routing|
|15||Hatched Blue||VDD (power) plane — not shown|
|16||Blue||Bottom: Mostly horizontal routing|
All of the VDD and GND nets have been routed. Ratsnest shows only 58 airwires remaining, though that will rise when I finish assigning inter-board nets to connector pins.
At this rate I could have both the ALU and ID boards completely laid out in a week or three. That assumes that I decide to keep using FDV301 and BSS83 FETs as high-side push-pull drivers and not switch to DMN26 parts.