40MHz is plenty for doom.
Ew, no. Even 386DX-40 is terrible for Doom:
Doom timedemo 386 DX 40 MHz DOS PC
486SX-33 is certainly playable, but you really want 486DX2/66:
Edit: grammar
Edit 2: These videos are accurate, btw. I upgraded from 386SX-25 to 486SX-33 just for Doom while my friend got the 486DX2/66 Packard Bell. Envy.
Edit 3: My memory forced me to go back and properly designate the models.
Are you sure you didn’t set low-detail with the viewport cranked way down? I played it on the same model
with a math co-processorand it could not handle high-detail and the large viewport in the video.Edit: I’m fairly certain I had a math co-processor, but I’ll defer to you on this detail just in case. That would certainly make a sizeable difference.