Having been plagued with the FPS curse myself I can only offer what I've found as to Arma 3 hardware /software related experiences.
First,
I started off with an AMD FX 8150 Black Edition and a ASUS Sabertooth 990FX motherboard and an AMD HD 7970 GPU. running in 5760x1080 resolution. With every other game this combination was decent enough to experience 60 +FPS in most shooters and MMO's with high to ultra graphical settings. Now comes Arma 3. With Arma 3 I was lucky if I got a stable FPS in the mid 30's- to low 40's with most settings recommended in this guide
http://day0.com.au/forum/arma/638-arma-3-performance-tweaks-and-settings-guide (as recommended in another post by PFC Montana) . This seemed to help a bit with mostly single player and the campaign, but even then often the FPS would dip widely into the low 20's when the bullets started flying, that is unacceptable. During our large scale operations my FPS would drop into the teens and single digits making combat impossible. The screen stutter as my pc tried to catch up to the rendering environment made it so I could barely react to contact. Now some of this performance hit is contingent upon the server, some on the assets created by Zeus, and then some on your hardware. So with everything going on it was hard for me to narrow down the actual root of the problem. After talking with other members of the 506th and watching their YouTube video's of large scale gameplay, I knew I couldn't solely blame it on the server, so i began to spend countless hours reading guides and tweaking my Arma 3 settings. Some of these changes and tweaks had marginal performance boots and others none at all, or actually worsened my gains I began to look at my hardware.
First I opted for a Amd R290x Gaming edition GPU which still wasn't that much of an improvement over my Amd HD7970. So then it was on to overclocking my CPU to 4.00 GHZ which did little to improve my FPS in most of our missions. I had kept reading comments about how AMD CPU's just did not work well with Arma 3 and at first I did not believe the authors thinking them fanboy's of Intel or boasting on their latest and greatest CPU's. However when a friend of mine who has an I7 was playing king of the hill with me side by side and getting much greater performance than I I knew it was time for a change.
So I picked up a bundle at NewEgg that offered an ASUS Z97 mbo and I7 4790K with 16gb Gskill ram for 660$ and set off to upgrade. After getting everything up and running I am now getting a solid 65-80 FPS in the campaign. I have not as of yet played with it in a 506th large scale mission but I can only assume there will be a significant FPS increase from what I'd been experiencing.
In closing, I wasn't sold on the AMD vs. Intel war in relation to Arma 3 but I can not refute the hard evidence of my performance gains from the upgrade. I did not want to fork out such a cash investment just for one game, but being that I love the gaming experience from Arma and the 506th it was kind of a "must do".
Sadly your CPU COMPLETELY matters in Arma 3. I hope this can help some people who are on the fence about upgrading their current hardware or contemplating making the switch to Intel . I know , I know, I should have waited for the next gen Intel and DDR4 but, I didn't want to sink even more money into a pc, nor play with shitty FPS until the price dropped.
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