Diagnosing SC2 Lag and Low FPS Issues - Click here

From my experimentation and experience the following are most dependant on each other and are the usual bottleneck suspects. These are the most common issues and main ones here on the forums pertaining to what hardware needs to be upgraded.

See asdf's guide to running SC2
READ FIRST: "can i run SC2?"


See TheXevs Troubleshooting
StarCraft II Troubleshooting FAQ


Alt-Tab Multi Task Lag - Ram Dependant
Low FPS - Mid-Late game - Mass units Lag - Cpu Dependant
Low FPS - High Res and Details - Video Card dependant

I thought I would post this as a general tooltip for people experiencing problems as when Sc2 first came out I had a host of problems and didnt know what to upgrade and what hardware was effecting my gameplay.

Alt Tab(Multi tasking)
Issue when Alt-Tabbing or mutli-tasking takes an extemely long amount of time to get into windows and or back into the sc2. I was running on 2gb ram only and was getting approximately 30-45 sec to multi task. Load times were also behind all other players after they were complete.
Fix - Upgrade to atleast 4gb ram.


Low FPS - Sudden Choppiness(Choppy, Laggy, slow)
Some players get extremely low fps during mid-late game, this is usually caused by the massive amounts of units, this part of sc puts strain on the cpu and which is probably why blizzards min specs are 2.6 dual core. Depending on your settings and resolution you may want to turn them down, but normal fps and a sudden decrease of fps during mid-late(many units) game is more likely to be the cpu bottleneck.
Fix - Upgrade Cpu to a dual core 2.6 or higher or get a better video card, sc2 does not utilize more than 2 core processors as of yet.


Low FPS - consistent in game choppiness
This is almost 100% due to the resolution and quality settings you are running at. . For example you can play with a Radeon 4670 on high settings but when you turn the resolution up to 1920x1080 it becomes choppy and laggy.
Fix - Upgrade your video card - The Geforce GTS 260 at $200 or Radeon 4870 at $150 are good enough for SC2 on Ultra Settings at a 1920x1080 resolution. The optimal card in value/performance is the Geforce GTX460 at about $240 Range and will give you better FPS at 1920x1080 or a bit higher, anything above the GTX 460 is overkill.

See Hardware Canucks Review On
StarCraft II GPU Performance Comparison

See Techspot GPU and CPU Performance in SC2
GPU & CPU Performance

See HD Starcraft Video Review and Recommendation -
EVGA Geforce GTX460


I didnt want wide screen users having a wider battlefield view advantage over me so I got a 23" lcd widescreen monitor. I got extreme lag in mid game to late game during 2v2 and higher with my P4 3.0GhzD, so I upgraded my cpu to a Core2Duo 2.9 and this eliminated the problem even in 4v4 mass unit battles. I had Alt tab issues in sc2 that would take 45sec to load back into sc2 so I upgraded from 2gb to 4GB memory and this eliminated the problem. I wanted to play on 1920x1080 res on med-high settings but got poor fps at this setting on my Radeon HD4670. I upgraded my vc to a GTX460 768mb and I am now running on ultra at 1920x1080 now with no limitations!

Minimum System Requirements*:

PC: Windows XP/Windows Vista/Windows 7 (Latest Service Packs) with DirectX 9.0c
2.6 GHz Pentium IV or equivalent AMD Athlon processor
128 MB PCIe NVIDIA GeForce 6600 GT or ATI Radeon 9800 PRO video card or better

Mac: Mac OS X 10.5.8, 10.6.2 or newer Intel Processor
NVIDIA GeForce 8600M GT or ATI Radeon X1600 or better

PC/Mac: 12 GB available HD space 1 GB RAM (1.5 GB required for Windows Vista/Windows 7 users, 2 GB for Mac users)
DVD-ROM drive
Broadband Internet connection
1024X720 minimum display resolution

*Note: Due to potential programming changes, the Minimum System Requirements for this game may change over time.

Recommended Specifications:

PC: Windows Vista/Windows 7 Dual Core 2.4Ghz Processor
2 GB RAM
512 MB NVIDIA GeForce 8800 GTX or ATI Radeon HD 3870 or better

Mac: Intel Core 2 Duo processor 4 GB system RAM
NVIDIA GeForce 9600M GT or ATI Radeon HD 4670 or better

If anyone has anything to add, please highlight in red and i can add to the above list, I am not a computer pro but this is what I have gathered from my experience and from those of others.