PC World - USA (2020-04)

APRIL 2020 PCWorld 99

individual PC builders. “Intel plans to

continue to publish the ATX Multi Rail spec to

maintain compatibility with existing

motherboards and power supplies to provide

the most options for our OEMs and

customers,” Intel officials told PCWorld.

WHY KICK 3.3 VOLTS

AND 5 VOLTS TO THE

CURB?

Still, eliminating the production of

3.3-volt and 5-volt power, or “rails,”

in the PSU itself is a major change.

PCs originally ran mostly on 5 volts,

but over time they’ve shifted mostly

to 12-volt power. One PSU maker, for

example, pointed to a circa-2006,

600-watt supply it made that had 25

percent of its power dedicated to

3.3-volt and 5-volt rails. Wind the

clock forward ten years,

and a similar 600-watt PSU

made by the same

company now budgets just

15 percent for 3.3-volt and

5-volt power.

Efficiency (how

effective the PSU is at

converting the AC from the

wall to DC that the PC

needs) has evolved, too.

The 2006 PSU operated at

78-percent efficiency,

while the 2016 PSU has a

98-percent efficiency rating. That means the

2006 PSU would have to consume about 127

watts of AC from the wall to generate about

99 watts, while the 2016 PSU would consume

about 100 watts to produce 98 watts of

power.

Because ATX12VO removes so many rails,

Comparing a 2006 PSU (left) with a 2016 version (right), we can see

voltages have trended away from 3.3- and 5.5-volt use toward 12-volt.

Intel’s new ATX12VO spec will feature a 10-pin connector

similar to the Compute Element connector.

2006-era 600 watt
PSU

25%

15%

75% 85%

2016-era 600 watt

PSU

3.3 Volt and 5 Volt rails 12 Volt rail