Testing the MIIG (
https://www.techpowerup.com/forums/threads/tpus-nostalgic-hardware-club.108251/page-533#post-4720644) was a handful. Seems the mATX layout plus late release with little support from Asus did it no good in terms of OC.
It did not even run 400 FSB with auto GTLs, and the problem became quickly apparent. The MCH reference line was impossible to get really stable, signal integrity is horrible on this board. With some tweaking I got 480 stable. With extreme tweaking and hours of playing with it I got a single 32m pass at 535, but this result was not reproducible. I got it to boot at 560, but it always freezes within 2 seconds. Higher VTT (1.24V+) makes it even more unstable. NB voltage does absolutely nothing. Impossible to boot this board with even just 1.3V VTT due to the signal quality issue. Like it literally stops working even below 400 FSB.
But in reality the ~500 FSB is still plenty for a normal setup. Air or water OC for a neat LAN-System is no issue.
Funny enough this E8500 is the hottest one I have. I actually ran into thermal issues with my water setup at around 1.5V and I had to disable LLC. With vdroop it hit 65°C core temps under load @ 1.40V. 230W system power draw. It has a 1.1V VID. Clocks okay but it stops scaling at around 4.8GHz / 1.4V.