By "MEMTEST" are you talking about MEMTEST64 that checks RAM modules for defects?
If it is then it isn't checking your CPU but rather your RAM Memory modules. One or more seems to be defective if you get that many errors.
I would remove all the RAM Modules and install one RAM Stick in A2 and then run Memtest64 to check it. If no errors then do the same for all the rest of your RAM memory to find out which is the one that is defective.
NOTE: Can also be a defective DIMM Slot on the Motherboard.
To check your new Processor download and run OCCT CPU Stress test. That will show you if you have any errors from your CPU or not.
I would run all three test to check your GPU and PSU while you are it.