If you want to play original doom 1.1 or 1.2 executable with no slowdowns then a souped up 486 might suffice. But with doom 2 ultimate doom and final doom a zero lag experience need a 100mhz Pentium at least.

Try to measure FPS, how many FPS you exactly have. There we can see, if it is really laggy, or you have some playable rate.
Yes, back in the time, we were less sensitive to less FPS, because so many games were going slow, we considered game playable even with 15 FPS. 20-25 FPS was considered smooth. Not, it moved above 30 FPS, particuallary, after we saw some super high FPS thanks to 3d accelerators.

As for minimum, for Doom, it's really DX 2 / 66 Mhz CPU, but with fast graphic card. Yes, bad graphic card, can limit your FPS. Particualary ISA VGAs, can drop your FPS to around 10 FPS level. With good graphic card, you should have around 30 FPS.

Here you can see examples of some really slow graphic cards, it is measured on Quake, but it will be similiar on Doom. On 486DX2/66 , try to take only those graphic cards, that are above 30 FPS in that table, otherwise, they will bottleneck whole PC.
https://www.vgamuseum.info/images/vlask/bench/quake320.png

wasn't CL settings of the MB and Write trough that made the DOOM slow on DX2? I use to play on the 486... seemed fine

W.x. wrote on 2023-11-14, 14:48:

Yes, back in the time, we were less sensitive to less FPS, because so many games were going slow, we considered game playable even with 15 FPS. 20-25 FPS was considered smooth. Not, it moved above 30 FPS, particuallary, after we saw some super high FPS thanks to 3d accelerators.

i think this is it, doom is playable at 25ish fps and back then we were all fine with it

most of the time i'm still fine with 30fps in most games anyway!

i payed doom and doom 2 all the way through on a p75 with 8mb ram (later 16) and some budget 2d pci graphics card, a friend had a 486-66 and all was well there too, suggesting this is a reasonable start point

Regarding RAM, the minimum for last map in DOOM 2 should be 8 MB (or be fast killing demons). In an 386DX 40 Mhz with 4 MB, the game continuously freezes a couple of seconds every 10 seconds or so writing to disk if there are a lot of enemies on screen.

For doom1&2 at 35 fps bare minimum is a 5x86 with fast pci or vlb , 8+ mb ram, better 16mb for smartdrv

But some? a lot? user maps will give problems in a stock 5x86, better pentium 100+ in this case or overclock

Minimum : 486 DX2/66 with VLB video card
Recommended : Cyrix 5x86 with VLB video card

I personally use FDOOM because I can (At the end, It's the same game, running of the same hardware).

I remember a friend on my software engineering class in '95 coming in with a P90 laptop and showing off how fast it was with Doom. The lads on the course were in awe of it, as pretty much the whole class was still stuck with 486 class CPUs. The offending classmate got the latest tech all the time, usually off the back of a lorry, so to speak. Everyone enjoyed it on their DX to DX4 systems, so it must have been enjoyable. I was never really a gamer, so didn't appreciate the boosted performance. I was still using a DX25 for coding, which was my primary interest at the time. Even now, other than playing Scrabble, I only have a collection of games for benchmarking purposes, but have never really even got round to that on most of my hardware