A "Full AT" motherboard is a rare and magnificent thing to behold. I've never actually owned a machine with one, I was always just enough behind the technology curve that I ended up with the smaller Baby AT models. I have worked inside some 386 systems with the full size boards bristling with DIP-packaged PALs and equipped with huge proprietary-slotted memory boards and you can't help but be a little impressed. They undoubtedly looked old the day they shipped but they were nonetheless "bleeding edge".

(I believe even the majority of IBM ATs actually had "baby AT" size boards, only the original "Type 1" was full size. There *may* have been 486s that big but by then I'm pretty sure the form factor was mostly extinct. Of course, watch someone prove me wrong with some monstrosity like a dual Pentium Pro in a full AT board.)

You want crazy, crazy overkill in motherboard form? Everex STEP MegaCube, circa 1991. 12 slots, 10 of which are EISA!