Want better performance in your game but don't want to tone down all settings to Lowest? Follow this guide that will (hopefully) make your game 10-15fps smoother! (NOTE: I apologize if there is already a guide on this, I don't look on the Technical Forums much now)

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Step 1. Turning down Antialaising (Edge Smoothing)
In your game options, there is an option called Edge Smoothing. If this is on High and you are getting bad performance, turn this setting down to Medium, Low or Off.
WARNING: This WILL make edges appear rougher if you turn this down but in my opinion, it is worth it for performance. Depending on the setting, you can expect up to a 10-15fps boost!
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Step 2. Setting the graphics card to Performance
In your graphics control panel you will most likely find a 3D Panel, set this to Performance and not Quality. This will give you a 3-6fps boost, so not as big of an effect but still nothing to scoff at! (This part is under construction as my Intel Control panel is not working at the moment so I cannot check!)

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Step 3.Setting the FPS lower
This isn't really going to give you a performance boost but if your fps are above 30 and you fluctate between 50-30 and notice lag or slowdown then download RivaTuner Statistics Server once you have that downloaded, click the + sign then find The Sims 4 game executable:

Go to "Devices and drives" and click on Windows (C:) or in Windows 7 Local Disk (C:) Or whatever drive you may have your Sims 4 installed to.

Click on "Program Files (x86)" and scroll down until you find a folder called Origin Games, click it and find The Sims 4 folder and click that too.

Then once you're in The Sims 4 game folder click on Game and then Bin and in RivaTuner click on TS4.exe



After that you will want to launch The Sims 4 and once it has launched, Alt+ Tab out of the game and pull up RivaTuner if it was minimized. Then find TS4.exe in the list and on the right panel find Framerate limit, you will want to click until this is at 30.
NOTE: The game will look slightly not as smooth as before if you look hard enough but in a game like The Sims it isn't really noticeable from my tests of this method in TS2.

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Step 4
Download a game booster, these game boosters can end programs running in the background and free up memory, here is some:
Wise Game Booster
Gboost
Razer Game Booster

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Step 5
Check and see that your antivirus is not auto scanning in the background.
When your antivirus does a scan it sets the scan to high priority most of the time and will take resources away from The Sims 4 and bog down performance horrendously, so check and see if that is causing the performance downgrade.

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Step 6 If your computer really is struggling with playing and processing your game, just give it a break and lower your settings. If you keep running like that for too long you could fry your graphics card thus causing you having to buy a new one or if its a on-board GPU possibly destroying your processor and causing you to buy another computer altogether

OTHER STEPS (Disclaimer: I did not type these)

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Step 7 Make sure that your power mode - not just your graphics card - is set to "High Performance" rather than "Power Saver" by clicking on the battery icon if on a laptop and selecting High Performance. Various parts of your computer will throttle themselves to the base clock speed in Power Saver, but will go into boost/turbo mode on High Performance. For example, Intel Processors with TurboBoost will typically run about 1GHz faster if needed in High Performance versus Power Saver. (Provided the processor is cool enough to power up without overheating.) If using a laptop, ensure that you are plugged in and not on battery power.

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Step 8 Keep your computer cool, literally. Modern components slow down when they get too hot to help prevent further heat build-up and hopefully avoid damage. You want to ensure that all of the fans in your computer are working (PSU fans, case fans, GPU/CPU fans, etc) and that everything stays within operating temperatures. If your game is crashing, or even your whole PC, that's a good sign that something is wrong and you should investigate.

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Step 9 Check what other applications are running when you are playing the game, and close anything you don't need. There are some programs, such as Razer's Game Booster, that will automatically close all extra processes when you open a game, and then restart them once you close out of the game.

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Step 10 Keep your hard drive defragmented. This will affect loading times more than actual game performance, but everything will load faster if the files are physically together on your hard drive. If your game files are broken up into hundreds or thousands of fragments, it takes the hard drive longer to find them and pull all of the fragments together when the game needs to load something - whether it be the entire world, or just that new CC you are trying to use.

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Step 11 Run the game in a slightly smaller window than your native resolution. The larger the game window, the harder your graphics has to work to fill the screen. Just dropping it down one size can free up tens of thousands of pixels and free up some of the stress from your graphics card/chip.
A few examples are that if you are playing at 1366x768, the GPU has to draw approximately 1,049,088 pixels! For a 1920x1080 (Full HD) Display it is just over 2 million. A resolution like 1024x768 has 786,432 pixels to render and is the minimum I could play at. A Resolution such as 800x600 only has your GPU render 480,000 pixels, there is 640x480 which draws 307,200 pixels but I do not recommend going below 800x600 for a playable experience (better yet I wouldn't really advise going below 1024x768)
If you have a PC this bad there is a few resolutions below 640x480 you could try such as 400x300 which makes the GPU render only 120,000 pixels but any resolution below 800x600 could possibly make menus display incorrectly or be cut off the screen.
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Step 12 When building lots, spread things out over multiple floors. The game will perform better with the less it has to render at once, so splitting your lots into multiple floors is a good way to cut that down.

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Step 13 If your computer is struggling with the game, use small lots. Avoid landscaping and don't furnish the house overly full of clutter and decorative nonsense you don't need.

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