I remember when I was younger I had always heard about how there existed 386SX systems with removeable CPUs. I would often rummage through junk bins in used computers stores looking for such a motherboard. This was before eBay listings had many pictures, and search engines didn't have an image search, so the ability to locate such things was extremely limited.
Even today, finding such a board is rare. From what I can tell, the majority of boards configured this way were in OEM systems. Every time I find a board like this on eBay, I try to document it. Needless to say, I haven't found too many. But during my searches, I occasionally noticed a 386SX board with solder pads for what looked like a test socket...but the pinout never seemed to be very consistent.
One day over 15 years ago I managed to purchase several desoldered 386 QFP100 test sockets that had a staggered pinout. I searched for a long time for a board that I could solder one onto. I think in all my searching I only ever found 1 or 2 boards that looked like they might accept my sockets, but I think both of them were very old and not worthwhile.
There are at least 4 or 5 pinouts for 386SX test sockets that I am aware of. They all seem to be about equally uncommon. I think I may have seen the one on your M396 on perhaps one other board. The most common one I run into is used by the military grade 386SX in PGA, which is also extremely rare.
"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium