Reply 540 of 578, by coolio
So in case anybody comes along later and sees my prior cry for help, I am happy to say my problem is solved. My conjecture that the 82c59 PICs were bad was false, as the ISA bus sourced interrupts issue was a red herring. After reading the 82c59 documentation, I learned that these chips have internal pull up resistors on the IRx lines. Hence, the ISA bus interrupts being held HI. Turns out my 80c88 chip wasn't working. I replaced it with a NEC V20 and I get a normal boot. Yay!
I'm not really sure how to determine whether I had a bad 80c88, or the wrong 80c88. The exact model I had was the Intel P80C88A-2. If anybody has some insights on this question, I'd love to learn.