download cpu-z and see what it says in there. If its still showing the wrong speed then try this if your using windows 8.1, which im guessing you are since its the only OS that shows ram speed in task manager.
In order for your RAM to operate at 2400, the motherboard needs to be able to support it and the processor needs to run at a speed that allows the proper combination of FSB speed and multiplier to get it to work correctly. All three components need to have the proper characteristics in order to function properly.
Advanced Option for Running the Memory Diagnostics Tool
The memory Diagnostics Tool run automatically and the advanced might want to adjust the Tool settings. These are given below.
a. When the Memory Diagnostics Tool starts, press F1.
b. You can adjust the following settings.
•Test mix choose what type of test you want to run Basic, Standard and Extended. The choices are described in the Tool.
•Cache Choose the Cache setting you want for each test like as Default, On or Off.
•Pass Count You want to repeat the steps type the number of times.
c. Press F10 to start the test.
Run Memory Diagnostic Tool in Windows 8. 1 and check.
a. Press Windows key and X key together, click on Control Panel.
b. Select the System and Security in the Control Panel.
c. Open the Administrator Tool, it is the last option under System and Security.
d. In the administrative tools window opened you have a show list of options from which click open the 'Windows memory diagnostic'.
e. Now you can see the option to check the memory errors and click the 'Restart now and check for problem' option, before that saved any unsaved work running your PC.
f. Once you select to restart, the windows memory diagnostic tool starts checking and restarts automatically displaying the result.
Hope this information helps you. Please do let us know if you need further assistance, we’ll be glad to assist you.
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