Also with the third generation, Intel introduced a low power version of its CPU. These chips were designed for battery powered laptop PCs and consumed less power than the SX or DX cousins.
The SL CPUs have important power-management features to conserve the batteries of laptops. The sleep mode function allows the CPU to turn your PC off while still sending power to RAM. When you turned your laptop back on, it would come back to exactly the same place as when it turned itself off.
Another power-management feature allows the CPU to turn off other components of the laptop if they are not used within a certain time. When needed, these components can be immediately turned back on.