ThinkPad T40 2378/2379-DxU 1GB PC2100 DDR Memory for IBM ThinkPad T40 2378/2379-DxU RAM-1GB 1024MB DDR 266MHz PC2100 200pin SODIMM 2.5v low heat the latest high density chips which draw less power and run cooler than other brands. This keeps laptop notebook run more stable.