neozeed: not 86box; 86box goes as fast as it goes, but in exchange even its dynrec is too high level for host cpu compatibility to matter much
zir blazer: ah, ok. I didn’t realize the significance of “unrestricted execution” and the sea change in how virtualbox worked with different hw virt versions; there is tons of guest instruction behaviour implemented in the hypervisor that it touches on and who can say what small difference has a knock-on
effect that leads to the crash

Also, its better to just create /root, edit /etc/passwd and change roots home to /root then copy all the files in /usr/X4/init over to /root appending a dot to each. Then you can edit the .xinitrc and .xserverrc files locally without messing with the system version.

I can confirm that Nano v1.0.9 builds and runs fine too.

The only feature that comes to my mind that Nehalem and above has and Core 2 generation lack is VT-x extension EPT (Extended Page Tables) for SLAT, which allows Nehalem to virtualize “unrestricted guest”.
https://forums.virtualbox.org/viewtopic.php?t=59379

must be the jit? Try 386/486 with no dynamic recompilation?

I had the same idea, because of the virtualized ISA devices involved, but the thing is, the exact same configuration works on my various other Core i’s and AMD systems, the only systems that give the triple fault are all of the Core 2’s I’ve tested (p9600, t9600, p7550) — there must be something special about them that hits this problem

it’ll be related to ISA DMA from the sounds of it. Many old 386 stuff lived in the 286 24bit address space, and didn’t take into consideration the memory layout as who on earth could afford more than 16MB of RAM back then, let alone fit it into their computer?!

old 386 BSD & Linux also suffered the same issues with DMA. You could try removing the floppy controller since it’s the larger source of DMA issues, along with forcing IDE into PIO mode as well, which will usually work up to the next big limit of 64MB.

But only with > 16MB of guest RAM; with 16MB of guest RAM the kernel boots and works fine (?)

Looks like Xfig.