The pattern of GYYY indicates that no memory modules are being detected during POST. It is possible that one or more of the memory modules has come loose in the socket on the mainboard or has failed. It is also possible that the system mainboard has failed, although this is less likely. You can troubleshoot this problem by re-seating the memory modules or uninstalling one of the memory modules to identify the real culprit. You may also try installing a known good memory module into each of the available slots to see if there is a problem with the mainboard.