I wouldn't just re-insert the old battery, but instead, try replacing with a new one.  Try replacing the RAM with new.  A-Tech is a brand I use and has a lifetime warranty. I used to have a 755.  It gave me the RAM error code, but reseating only worked for so long, so I upgraded the RAM with new and it worked great.   [IMAGE]  
Hi all, This is my first post so forgive me for any obvious information omission i.e. critical info for diagnosis I have a 2011 Dell Optiplex 990 Mid tower. A few months ago it kept throwing up error messages on ePSA that my memory bus had failed, CPU cache had failed, and so had one stick of memory, yet this was 2 of 3 times, and the other times it would boot up Windows 10 but shut down randomly.  Before this it worked with Windows 10 fine after a botched upgrade that I managed to sort out once I changed some basic BIOS settings. Yet before this it ran it's native Windows 7, which was fine for about 2 years then started randomly turning on and shutting down, whenever it was plugged in, which was very annoying but manageable. And all it did was sit at either the lack screen or Startup repair, the former shutting out user input, and the latte continually failing to fix anything or even send any diagnostic data due to the iffy WiFi card (which I have since replaced with a much better USB WiFi dongle). Now it gives me lights 1 and 3 and a blue light power button. But I have changed and reinstalled the ram several times, and removed and reinstalled the CMOS battery, so I am utterly losing my patience. Should I attempt to fix it in its current state, buy new parts for the 10 year old pc (turning 11 this October) or would it be best to start afresh with a new pc? I also run a 2011 Seagate Barracuda 500gb and a 2011 Samsung Pro128 12gb as the boot drive, along with a 2019 Gigabyte Radeon RX570 graphics card. The pc is easily powerful enough for anything I throw at it, which is older and smaller games  (notably Rigs of Rods and Roblox), Web browsing or general processing tasks such as word or A7dacity occasionally. Again, should i get rid or keep with it? Thanks a bunch, Alister
Is it completely broken?