Panic on i386 kernels using legitimate 486's/workaround.

["William D. Jones" <thor0505%comcast.net@localhost>]

Hello all,

I know a few users including myself run NetBSD's on 486's and old systems 
just to keep them doing useful work, so I thought I would signal-boost a 
problem I had with a (long overdue) kernel upgrade that I had this morning 
(see also: http://gnats.netbsd.org/49104), so that it's easier to find the 
solution for now until (hopefully) a patch gets accepted back into the main 
tree.

The relevant bug report is here: http://gnats.netbsd.org/49124

Running kernels after August or so result in a nice panic on 486's: 
"privileged instruction fault in supervisor mode". In short, a change back 
in August disabled a check for a 486 CPU that causes an illegal instruction 
on 486's (RDTSC). The submitter of the above bug report adds the check back 
in, so we can now use 486 CPUs again- a very important CPU target for NetBSD 
:) It does not appear there has been any activity on the bug report since 
then.

I hope a workaround or solution gets accepted back into the tree so that 486 
support remains working (akin to continued 68k support). While I understand 
that someone running NetBSD on a 486 is likely to use current and not an 
official release, I know I would've been frustrated if the first thing I saw 
6 months ago was a panic that could be fixed by a single line of C code.


Sincerely,

--
William D. Jones