Intel's Slot 1 CPUs are currently the fastest CPUs available for PCs and Slot 1 is a CPU interface patented by Intel. This is why there is no other CPU manufacturer producing Slot 1 CPUs currently. Slot 1 offers Intel's GTL+ bus protocol, known from the Pentium Pro CPU, which hosts the so called dual independend bus (DIB), which means that the Slot 1 CPUs have one bus which they use to communicate with the memory and system devices like the PCI and AGP bus and another bus for communication with the second level cache, which is built into the Pentium II CPU cartridges. GTL+ is particularly helpful for multi CPU systems and is a protocol that is patented by Intel as well. This means to other chipset manufacturers that they have to license the GTL+ protocol from Intel if they want to design their own Slot 1 chipsets.