Power Supplies - Upgrading and Repairing PCs - page 866

18.6 ).
Figure 18.6. PS3 (SFX/SFX12V) power supply with internal 80mm fan.
SFX120V power supplies are specifically designed for use in small systems containing a limited
hardware and limited upgradeability. Most SFX supplies are designed to provide 80-300 watts of
continuous power in four voltages (+5V, +12V, -12V, and +3.3V). This amount of power has proven
to be sufficient for a small system with a processor, an AGP or PCI Express x16 interface, up to four
expansion slots, and three peripheral devices—such as hard drives and optical drives.
Although Intel designed the SFX12V power supply specification with the microATX and FlexATX
motherboard form factors in mind, SFX is a wholly separate standard that is compliant with other
motherboards as well. For example, the PS3 variant of SFX12V can replace standard ATX12V
power supplies as long as the output capabilities and provided connectors match the system
requirements. SFX power supplies use the same 20-pin or 24-pin connectors defined in the
ATX/ATX12V standards and include both the Power_On and 5V_Standby outputs. SFX12V power
supplies add the 4-pin +12V connector for CPU power, just as ATX12V supplies do. Whether you
will use an ATX- or SFX-based power supply in a given system depends more on the case or chassis
than the motherboard. Each has the same basic electrical connectors; the main difference is which
type of power supply the case is physically designed to accept.
EPS/EPS12V
In 1998, a group of companies including Intel, Hewlett-Packard, NEC, Dell, Data General, Micron,
and Compaq created the Server System Infrastructure (SSI), an industry initiative to promote industry-
standard form factors covering common server hardware elements such as chassis, power supplies,
motherboards, and other components. The idea was to be able to design network servers that could
use industry-standard interchangeable parts. You can find out more about SSI at www.ssiforum.org .
Although this topic does not cover network servers, in many ways a low-end server is a high-end PC,
and many high-end components that were once found only on servers have trickled down to standard
PCs. This trickle-down theory is especially true when it comes to power supplies.
In 1998, the SSI created the entry-level power supply (EPS) specification, which defines an industry-
standard power supply form factor for entry-level pedestal (standalone tower chassis) servers. The