head -r339076's boot loader fails to boot threadripper 1950X system (BTX halted); an earlier version works

[Mark Millard]

I attempted to jump from head -r334014 to -r339076
on a threadripper 1950X board and the native
FreeBSD boot failed very early. (Hyper-V use of
the same media did not have this issue.)

But copying over an older /boot/loader from another
storage device with a FreeBSD head version that has
not been updated yet got past the problem being
reported here. (For other reasons, the kernel has
been moved back to -r338804 --and with that,
and the older /boot/loader, the 1950X native-boots
FreeBSD all the way just fine.)

For the BTX failure the display ends up with
(hand transcribed, ". . ." for an omission):

BTX loader 1.00 BTX version is 1.02
Console: internal video/keyboard
BIOS drive C: is disk0
. . .
BIOS drive P: is disk13
-
int=00000000  err=00000000  efl=00010246  eip=000096fd
eax=74d48000  ebx=74d4e5e0  ecx=00000011  edx=00000000
esi=74d4e380  edi=74d4e5b0  ebp=00091da0  esp=00091d60
cs=002b  ds=0033  es=0033    fs=0033  gs=0033  ss=0033
cs:eip=66 f7 77 04 0f b7 c0 89-44 24 0c 89 5c 24 04 8b
       45 08 89 04 24 83 64 24-10 00 c7 44 24 08 01 00
ss:esp=00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00
       00 00 00 00 00 00 00 00-f0 1d 89 00 00 00 00 00
BTX halted


The board is a GIGABYTE X399 AORUS Gaming 7 (rev 1.0).
It has 96 GiBytes of ECC RAM, just 6 DIMMs installed.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)