soooo i've been getting back into minecraft recently and when i first tried to run Infinity (1.8.2) it would crash before it got out of the Mojang screen. i redownloaded the FTB launcher, the modpacks, and Java and basically started fresh and now i'm able to get into single and multiplayer, but in both there is severe slowdown in the game and for the rest of my computer, and sometimes minecraft will still crash (some particle effects, specifically in Genetics, seem to be broken, but maybe that's just the mod).
i've messed with the graphics and performance settings a lot, basically setting everything as low as possible, and it didn't really help much. i installed optifine, didn't do much, disabled threaded optimization in the NVIDIA control panel (i had to do that a couple years ago when i was using the Monster modpack, figured it might help here too) also nothing. my computer is barely a year old and it ran Infinity perfectly fine in January and i don't know what could have happened between then and now to change the performance so much. the only improvement i've noticed is there's a small (~10x10 block radius) area in the server i'm in where if i'm looking into the center of that area my framerate will be fine, but everywhere else it's terrible.
here's my computer's specs (not sure if this is everything relevant):
Windows 7 Home Premium (x64) Service Pack 1 (build 7601)
Install Language: English (United States)
System Locale: English (United States)
Installed: 8/4/2014 10:56:42 AM
Boot Mode: Legacy BIOS in UEFI (Secure Boot not supported)
2.80 gigahertz Intel Core i7-4810MQ
256 kilobyte primary memory cache
1024 kilobyte secondary memory cache
6144 kilobyte tertiary memory cache
Multi-core (4 total)
Hyper-threaded (8 total)
Intel® HD Graphics 4600 [Display adapter]
NVIDIA GeForce GTX 860M [Display adapter]
Generic PnP Monitor (15.3"vis, January 2012)
can anybody help me fix this?