I played it back when it came out on a P166 in software mode and it was fine at that resolution.
Like I remember Doom running fine on my 486 SX 25Mhz, but looking back at it now, it wasn't that great. It took a top end Pentium to really get it into smooth-ish 20fps+ territory.
DOOM wasn't fine on Am486DX4 100MHz and Ziggurat Vertigo was like 5fps at best on it.
Are you happy now?