When I turned on my PC, there was an error telling that “the following are warnings that were detected during this boot. These can be viewed in setup on the event log page…
WARNING: memory size decreased…
Press Enter to Continue…
Agree with others: probably a loosely seated memory module or a faulty one.
try to remove the RAM module and clean it and then place it again
several reasons can produce this message such as memory require reseating (unplug, replug) or is bad or perhaps motherboard have problems.
you can try to reset cmos
Test Your Computer’s Memory For Errors with Memtest
Since the errors showed up during POST, using memtest will only be testing the memory that BIOS found when the system was booted. The additional memory that BIOS failed to see won't be tested anyway.
testing them together and testing them one by one can give more indications
the problem may also appear when system entering in dual channel configuration, the problem could be from the processor?
It appears that the amount of RAM that was detected during POST on your previous boot (which is saved in the BIOS) was not matched on the boot in question. The most common reason is that one or more of your DIMM modules was not detected properly because it has become unseated or has otherwise lost its electrical connection with one or more pins or that the memory module itself has failed. You should reseat all modules and see if the BIOS detects all of the installed RAM first. If it is still not detecting all of your RAM, you should try each module individually to find out what one(s) is (are) causing the problem.