Hardware Reference
In-Depth Information
Thismeansthetotalpower-handlingcapacityofthisconnectoris373wattsusingstandard
terminals or 560 watts using HCS terminals, which is substantially higher than the 251
wattsavailableintheprevious20-pinconnector.Combiningthe24-pinmainandthe4-pin
+12V power connector results in up to 565 watts (standard terminals) or 824 watts (us-
ing HCS terminals) total power available to the motherboard and processor! This is more
than enough to support the most power-hungry motherboards and processors on the mar-
ket today.
CPU Power Connectors
Power for the processor comes from a device called the
voltage regulator module (VRM)
,
which is built into most modern motherboards. This device senses the CPU voltage re-
quirements (usually via sense pins on the processor) and calibrates itself to provide the
proper voltage to run the CPU. The design of a VRM enables it to run on either +5V or
+12Vforinputpower.Manyhaveused+5Vovertheyears,butstartingin2000mostcon-
verted to+12Vbecause ofthelowercurrent requirements atthat voltage. Inaddition, oth-
er devices might have already loaded the +5V, whereas only drive motors typically used
the +12V prior to 2000. Whether the VRM on your board uses +5V or +12V depends on
the particular motherboard or regulator design. Many modern voltage regulator ICs are
designed to run on anything from a +4V to a +36V input, so it is up to the motherboard
designer as to how they will be configured.
Forexample,IstudiedasystemusingaFirstInternationalComputer(FIC)SD-11mother-
board, which used a Semtech SC1144ABCSW voltage regulator. This board design uses
the +5V to convert to the lower voltage the CPU needs. Most motherboards use voltage
regulator circuits controlled by chips from Semtech (
www.semtech.com
) or Linear Tech-
nology (
www.linear.com
)
. You can visit their sites for more data on these chips.
That motherboard accepted an Athlon 1GHz Cartridge version (Model 2), which accord-
ing to AMD has a maximum power draw of 65W and a nominal voltage requirement of
