HP 8000 HP Enterprise/Mid-Market Desktop PC Power Supply Architecture - Page 9

Product Optimization Common MT and CMT Power Supply In the 2008 HP business PC product lineup, the CMT used a different power supply, as did the MT. To improve product leverage and efficiency, the 2009/2010 generation CMT and MT platforms share a common power supply. One obstacle to leveraging power supplies between multiple chassis is the quantity and location of the expansion optical and hard drive bays. The drive power cable is typically provided directly by the power supply. The length of the cable, quantity of connectors, style of connectors (right-angle vs. straight), and spacing between connectors is unique to each form factor. Form factors are unlikely to be capable of sharing a power supply unless the drive power cables can be detached from the power supply. By moving the drive cables from the power supply to the motherboard in the new power supply architecture, each chassis is allowed to implement its own drive power cable to meet its needs and then share the power supply. SFF Cable Routing The SFF power supply rotates back to allow access to the primary hard drive and overhangs the motherboard, which creates height constraints on connectors placed under or near the power supply, such as the power supply connectors. The dynamic positioning of the rotating power supply feature requires flexible cabling between the power supply and the motherboard power connector. If the cable bundle is stiff or taut, it will interfere with the movement of the power supply and stress the connectors and cable routing within the system. The flexibility of the power supply cables is a function of the quantity of wires going to the connectors and the length of the cable. More wires create a less flexible cable. Shorter wires in smaller form factors also create a less flexible cable. The previous SFF products suffered from both of these issues. The new power supply architecture removes +5V and +3.3V voltages and control signals from the primary high power connector, reduces that connector from 24-pins to 6-pins, and relocates the peripheral cables to the motherboard. As a result, the cable density and flexibility of the cable assembly is significantly improved. +5V and +3.3V Operational Voltages The importance and use of +5V and +3.3V have changed significantly since the ATX specification was first introduced. These voltages are primary used by legacy and I/O devices, but are only used sparingly, if at all, by newer technologies, chipsets, processors, and internal communication protocols. Electronic component and silicon technology, as well as power management techniques, have advanced beyond the need for +5V and +3.3V as the primary voltages. The majority of power consumed by a motherboard comes from operating voltages below +3.3V and more voltage levels are reduced nearly every year. As an example, the memory operating voltage has fallen from +2.5V (DDR) to +1.8V 9