What does 3-phase power, 4-phase power mean for mainboards?

[uOpt]

Can somebody explain what it means when people say a certain mainboard has 3-phase power or 4-phase power? Obviously it's not A/C phases.

Thanks.

[CAD4466HK]

Your older Socket A and Xeon boards went from 2 phase regulators{load spread accross 4 MOSFET's} to 3 phase{load spread accross 6 MOSFET's}
and so on. More load accross more MOSFET's equals less heat and longer
life for your board, they still incorperate this in todays boards:)

[madmat]

A few have 8-phase regulation :D

[GalvanizedYankee]

An Albtron limited edition or a Gigabyte has 12-phase but that's probably just for the bragging rights.
I did see one or the other posted at badcaps. It was probably the Albatron.

[GalvanizedYankee]

http://www.badcaps.net/forum/showthread.php?t=2646 You might have to register to see the one attachment, it does add an understanding to the topic. If you do register over there, give Galvanized the referral please.


Hope I'm not out of line jonny.:cool:

[Micutzu]

Can somebody explain what it means when people say a certain mainboard has 3-phase power or 4-phase power? Obviously it's not A/C phases.

Thanks.

They refer to the CPU voltage regulator, that creates a voltage in the range from under 1V upto even 2V at a current that can reach 200A (for the new digital regulators), using as input the +12V line coming from the system PSU.
These circuits contain a number of buck converters (some tech info and calculations here (http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/abw_hilfe_e.html)), each generating the same voltage and a split of the total output current. Each converter usually consists of 2 or 3 switching MOSFET transistors, one coil and at least one capacitor, plus the driver section wich can be either separate or included in the main PWM controller. The buck converters do not work synchronised but with an equal delay betewen eachother's switching, reason for wich every converter is also called "a phase".
The advantages of using multiple phases are many, the most important being the reduction in output capcacitor size. As i said, each converter takes it's turn in switching, making the output ripple's frequency much higher due to phase interpolation. For example, if we have a converter that works at 500Khz, for a single-phase topology we would have 500Khz ripple, but for let's say 4-phase topology the ripple would be at 2Mhz ... this would theoretically necessitate 4 times smaller output capacitors, making the design less expensive and more compact.
Another advantage of the phase interpolation process is that the response at load transients will be much better, wich is an important factor for CPU voltage supplies. Also, the fact that the current is drawn from more converters means lower power parts and better heat dissipation spreading across the PCB.
There are also limitations, very high-frequency ripple means more EMI and necessitates better capacitors for output filters, making the design more expensive (wich we were trying to avoid in the first place). There are also digital switchers that you can see on few of the latest motherboards, that switch at very high frequencies and use ceramic capacitors, also being very efficient and generating very little heat.
My guess is that with today's parts and CPU power requirements 6 phase analogic or 8 phase digital should be standard for high-end motherboards, less would be cost reduction and more would be overkill. Gigabyte's 12-phase analogic design seemed ridiculous at the time, as people were still establishing overclocking records with FX-60's on 3-phase DFI's. As a matter of fact, i have a huntch that Gigabyte's 12-phase was actually a 6-phase with 2 converters per phase.