I've tried to find a solution, but I haven't had much luck. The photo says it all:
I'm supposed to have 4 cores, but they're not showing up. What gives? msconfig advanced boot options also only show one processor.
Windows 8.1 Task Manager – How to Show Multiple Cores
cpuwindows 8.1
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"It seems like I am stuck here! Is there any way I could access my data and back it up on external HDD? I will try any suggestions you have!"
Boot from a different operating system. This could be another Windows installed on another partition, or it could be something like these:
You can then mount your harddisk and copy the files to an external HDD, as long as your hard disk is not encrypted.
First, it's probably not actually not 8 cores but 4 cores 8 threads, unless you're using some CPUs without Hyperthreading. You can see the number of cores and threads in the performance tab of Task Manager. The CPU usage in that tab is also a combined value for all the CPUs by default. Just right click > Change graph to > Logical processors
Best Answer
There are a number of things that can cause this, and here are several possible fixes.
ACPI bugs in your motherboard's BIOS can cause this problem. Ensure that you are running the latest BIOS/firmware for your motherboard.
On that note, did you upgrade Windows recently? If so, then you may need to update your chipset drivers.
In msconfig, uncheck the box to set the number of CPU cores. Then shut down the computer.
A third party utility called EasyBCD can reset the number of CPUs Windows thinks it has. Despite it apparently controlling exactly the same thing, this has been known to work when the msconfig setting above failed.
When you power on the computer again, Windows should figure out how many CPUs you have and fix itself.
Another possible fix is to delete your CPU from Device Manager, and then restart your computer. This causes Windows to redetect your CPU, hopefully correctly.
While you're in Device Manager, see if anything else is reporting a problem, and fix it.