• ECC Unbuffered (The "E"): The "E" in 12800E is very important. These are ECC (Error Correction Code) modules. They are typically designed for workstations or servers.
• Compatibility Warning: Because these are ECC sticks, they will not work in most standard "home" or "gaming" motherboards. Most consumer PCs require "Non-ECC" or "Unbuffered" RAM. If you try to plug these into a standard office PC, it likely won't boot.
• Voltage: These are PC3L, meaning they run at a lower 1.35V compared to the standard 1.5V DDR3. They are backwards compatible with 1.5V systems, but it's a nice efficiency perk.