Hardware Reference
In-Depth Information
clock speeds ranging from 3.2GHz to 3.4GHz (Socket 478) and from 3.4GHz to 3.73GHz (Socket T).
Pentium 4 Power Supply and Cooling Issues
Compared to older processors, the Pentium 4 requires a lot of electrical power. Because of this,
starting in February 2000, Intel changed the ATX motherboard and power supply specifications to
support a CPU voltage regulator module powered from 12V instead of 3.3V or 5V, as with previous
designs. By using the 12V power, more 3.3V and 5V power is available to run the rest of the system,
and the overall current draw is greatly reduced with the higher voltage as a source. PC power
supplies normally generate more than enough 12V power, but the previous ATX motherboard and
power supply designs originally allotted only one pin for 12V power (each pin is rated for only 6
amps), so additional 12V lines were necessary to carry this power to the motherboard.
The fix appears in the form of a CPU power connector called the ATX12V connector. Any
motherboard having the ATX12V connector requires that you supply power to it. If you are using an
older ATX power supply that lacks the proper ATX12V connector, several companies sell adapters
that convert a standard Molex-type peripheral power connector to the ATX12V connector. Typically,
a 300-watt (the minimum recommended) or larger power supply has more than adequate levels of
12V power for both the drives and the ATX12V connector.
If your power supply is less than the 300-watt minimum recommended, you may need to purchase a
replacement supply.
See the
Chapter 18
section, “
Motherboard Power Connectors
,
”
p.
870
.
Cooling a high-wattage processor such as the Pentium 4 requires a large active heatsink. These heavy
(sometimes more than 1 lb.) heatsinks can damage a CPU or destroy a motherboard when subjected to
vibration or shock, especially during shipping. To solve this problem with Pentium 4 motherboards,
various methods have been used to secure the heatsink in the system. Intel's specifications for Socket
423 added four standoffs to the ATX chassis design flanking the Socket 423 to support the heatsink
retention brackets. These standoffs enabled the chassis to support the weight of the heatsink instead of
depending on the motherboard, as with older designs. Vendors also used other means to reinforce the
CPU location without requiring a direct chassis attachment. For example, Asus's P4T motherboard
was supplied with a metal reinforcing plate to enable off-the-shelf ATX cases to work with the
motherboard.
Socket 478 systems do not require special standoffs or reinforcement plates; instead, they use a
scheme in which the CPU heatsink attaches directly to the motherboard rather than to the CPU socket
or chassis. You can install motherboards with Socket 478 into any ATX chassis; no special standoffs
are required.
Socket T (LGA775) systems use a four-side frame-locking mechanism that holds the processor in
place. The heatsink is positioned over the processor, and locking pins attach it to the motherboard.
Later LGA sockets use a similar design.
Because the Pentium 4 processor family has been manufactured in three socket types with a wide
variation in clock speed and power dissipation, make sure that you choose a heatsink made
specifically for the processor form factor and speed on a particular system if you need to replace a
heatsink.
Intel Pentium D and Pentium Extreme Edition
Intel introduced its first dual-core processors, the Pentium Extreme Edition and Pentium D, in May
