Tyan Tomcat IIID Dual Pentium 166mmx Double Fault on Boot

[Alexander Jacocks <jjacocks%gmail.com@localhost>]

Folks,

I've been trying to bring up NetBSD (both 9.x and 10.x) on my vintage Tyan Tomcat IIID (https://theretroweb.com/motherboards/s/tyan-s1563d-tomcat-iii). Either via floppy boot or CD boot, the initial bootloader comes up and loads the kernel, and then after the screen clears, I see this:

[  1.0000000] fatal double fault in supervisor mode

[  1.0000000] trap type 13 code 0xc011451d eip 0x8 cs 0x202 eflags 0x10 cr2 0 i
level 0 esp 0x30
[  1.0000000] cur lwp 0xc1285600 pid 0 lid 1 lowest kstack @xc15602c0
kernel: user trap double fault, code=0 Stopped in pid 0.1 (system) at 8:

invalid address

Does this likely have to do with the oddity of a dual Pentium system? It's an Intel 430HX chipset with 56MB of RAM. RAM seems OK, and I have parity enabled, and other OSes seem to boot and run OK, including use of a bunch of RAM.

Thanks!

- Alex