Hey guys, been having no trouble with both games in vanilla state (no mods, changes to configuration, etc.) on my main 6700K and GTX 1080 rig. But for whatever reason the performance when running on my secondary/htpc machine is much more laggy despite it still being beyond whatever these old games might need. Have no idea why it's fine and smooth on the main, but the other machine has frequent fps drops here and there. Anybody here running similar combination maybe?

Just to clarify. Are you having real fps drops or just micro stuttering? Did you try running some software which shows how many fps you have?

Yes, not a microstutter. Running Afterburner OSD and see frequent drops from 60 into 40-50ish area, that are somehow noticeable even though I'm using a 1080p g-sync monitor. The fps is limited to 60 through AB as well (cause it goes beyond otherwise). For some reason I don't see these drops on my main rig (with 1440p g-sync monitor) and the gameplay there is smooth. CPU/GPU utilization is low on both machines as expected, so I'm at a loss where's the difference coming from. I've also noticed that performance is worse when news on the radio are playing.

This probably has something to do with drivers. I'd start with the audio ones. If you have the newest available drivers you could try installing the older ones. It wouldn't be a bad idea to experiment with graphics drivers as well. You should have way above 60 fps. You don't have such problems with other games do you?

Already tried without g-sync and doesn't really do anything. As I noted before, no problem with main rig using g-sync monitor there too. Using W10 latest build. You have 4 cores, while g4560 is 2/4. If I'm not mistaken, I think I saw somewhere that old gamebryo games specifically don't like such configuration. Might be the reason in my case? Both rigs are up to date in terms of drivers. No problems with any modern games on this secondary PC, only these old fallouts. I don't have an issue with the audio, it's just that I noticed whenever news on the radio come up - fps drops a bit and improves if I turn the radio off. Might be something with iNum multi-thread setting for the radio? Think it just doesn't like 2/4 CPU, but has no issue with 4/8 on the main.

Okay, let's tweak the game a bit to allow it to use more ressources.

Open the Fallout3.ini file usually located in Documents\My Games (could be slightly different, I have not the game installed yet). Don't forget to make a backup of it before going further.

Try to make these few modifications:

bEnableAudioCache=1
iAudioCacheSize=2048
iMaxSizeForCachedSound=256

This should help with audio issues. Then:

uInterior Cell Buffer=16
uExterior Cell Buffer=102
iPreloadSizeLimit=104857600

These ones are for memory optimization, note that those values are optimal with 2Go of RAM, which is enough for Fallout 3. Feel free to increase again (multiply each value by 2) for testing with 4Go.

Next step:

bBackgroundLoadLipFiles=1
bLoadBackgroundFaceGen=1
bBackgroundCellLoads=1
bLoadHelmetsInBackground=1
iBackgroundLoadLoading=1
bBackgroundPathing=1
bBackgroundNavmeshUpdate=1
bCloneModelsInBackground=1

Make landscape more easy to load for your computer.

bUseThreadedBlood=1
bUseThreadedMorpher=1
bUseThreadedTempEffects=1
bUseThreadedParticleSystem=1
bUseThreadedAI=1
bUseMultiThreadedFaceGen=1
bUseMultiThreadedTrees=1
bMultiThreadAudio=0
iNumHavokThreads=5

This is for multithreading effectiveness.

Let me know if it helped!