DRM error in cpt_serr_int_handler, failure to boot NetBSD 7.99.71

["Thomas Mueller" <mueller6725%twc.com@localhost>]

Trying to boot a newly-updated NetBSD-7.99.71 installation fell short on a computer with Intel Ivy Bridge CPU, for both amd64 and i386.

Generic kernel went into immediate reboot with no messages showing, while my custom kernel failed at or near the end.

No /var/run/dmesg.boot, but I was able to read what was visible within the range that Scroll Lock and PageUp would permit.

I saw message
DRM error in cpt_serr_int_handler: PCH transcoder A FIFO underrun
ERROR: 400 cycle TSC drift observed

...

WARNING: 9 errors while detecting hardware: check system log

This was for both amd64 and i386.

I searched for "DRM error in cpt_serr_int_handler

on duckduckgo.com

results were nearly all for Linux and related to Intel Ivy Bridge and Sandy Bridge.

Surprise came when I copied new kernels to other computer, Intel Sandy Bridge, via NFS, running from build host using NetBSD 7.99.1, and they proved bootable for the Sandy Bridge.  I booted only the custom kernels, didn't try the generic.

I was able to install the userland via NFS using build.sh on i386 but failed on amd64.  I haven't got to testing this yet to see if/how it boots with the updated userland.

I looked on the NetBSD emailing lists but saw nothing.  Maybe this is an allergy peculiar to a narrow range of CPUs?

I thought I'd just have to lay NetBSD aside in favor of FreeBSD for a few months until I tried and was surprised when custom kernel 7.99.71  booted on the other (Sandy Bridge) computer.

Tom