Yeah, it's a real pain! I suspect they just ran out of pins. I don't think there's a single pin on that package that I'm not using!
I've thought about the power-cut approach too, my big concern about it would be making sure that power stays off for long enough to fully reset the chip - the datasheet is rather vague on the relevant specs there, so it'd probably be a case of having to figure it out experimentally.
Disabling the chip's interrupt line in the glue logic until the driver has signaled that it's ready feels pretty bad too, although Macs pull a similar trick to temporarily map ROM into RAM during early boot, so I don't feel *too* guilty about using it.
Funny you mention that, I threw together a PrimaryInit routine to try that as an experiment, but I've been too lazy to pull the ROM out and reprogram it

. It's not clear to me exactly when in the boot process the Sad Mac happens relative to when PrimaryInit code runs, so I'm not quite sure if it would help, but it'd be an interesting experiment.
For now, I've written a
brute-force Shutdown Manager routine that resets the chip. It's not going to do any good on a system that's hung, but it does the job for a normal restart.
I still need to actually build the SE version of the card and get that working - just need to get my SE working first, as it suffered a hard disk failure the day before the boards arrived! As it turns out, the IIfx has been the ideal test mule for hardware bringup - much easier access to the PDS slot than on a Compact Mac, and its tighter timing specs have brought to light a few issues that I'd probably not have noticed otherwise.
I just took a look at the MagicBus pinout, and from what I can tell, a MagicBus version of the card is absolutely viable. If folks are interested, and someone with a suitable accelerator could assist with the development and testing, I'd be happy to collaborate. I'd like to get Revision 1 of the regular SE and SE/30 boards out of the way first, but keep reminding me about it!
That actually brings me on to another thing I've been thinking of - the issue of licensing. Right now I'd strongly recommend that against building or basing designs off of the Revision 0 design, just because it's not finished and Revision 1 will likely introduce some incompatible changes. But once that's done, I'd like to officially release the project under some kind of open hardware license. Based on interest, I'll likely do a small production run to sell, but if people want to build it themselves or adapt the design for their own projects, I'd like to encourage that. This is all new territory for me, so if anyone's been through this already with a hardware project, I'd really appreciate any wisdom or pointers - at this point I'm not even sure which license to choose.