Silly NIC games ...
“My new Intel 386 was so much faster than the 286 machines on the floor that it was grabbing every packet on the LAN,”
Yeah, I ran across those poorly made NE2000 clones, too. It wasn't your processor, it was your NIC not playing well with others.
I got two boxes of 20 NICs once. Installed 'em into 40 new "beige box" PCs, and set 'em up as two test networks of 20 PCs each. All went swimmingly. Until I connected the two networks, at which point both halves refused to work. Long and short of it, the two boxes of NICs duplicated 20 total MAC addresses. Yes, it took a while to figure out. Yes, I was more than slightly irritated with the vendor ...