These design guidelines include layout rules and hints based on system design experience. They do not define a specific card design nor constitute a specification. Card designers will still need an understanding of the system the card will be used in, as well as the customary simulation and system testing. In the following four-way symmetric multi-processing (SMP) design example, all processor system bus AGTL+ signals are tied to +1.5V through a 150 W resistor, so that the bus maintains a 25 W impedance no matter what configuration is used in the five available slots. For a two-way SMP design (i.e. dual processor), the cluster controller connector is not needed. A two-way SMP design would simply have two processor locations and the 440GX AGPset or 450NX PCIset.