My friend just gave me a computer. The motherboard is Asrock M266A
with P4 2.8 CPU
The motherboard does not have 12V power connector for P4 CPU and there
are only 4 mosfet next to the CPU.
The capacitor is Chemicon KZE and KZG.
Q1.I am just curious why a 12V P4 connector is not needed for this
board.
Q2. And why there are only 4 mosfets instead of 6 or 8?
Q3. I heard people say Asrock is crap? Any comment?
Q4. The board is about 3000 hours old(i check it with using smartctl,
same age as hard drive; both bought together)
Will a 4 mosfet desgin last for >20000 hour of operation under p4 2.8
Ghz CPU?
Picture
http://www.geocities.com/saturnlee/Repair/AsrockM266A/3.JPG
http://www.geocities.com/saturnlee/Repair/AsrockM266A/2.JPG
http://www.geocities.com/saturnlee/Repair/AsrockM266A/1.JPG
In terms of input power sources, let's assume each pin is rated
at 6 amps on the two ATX power connectors.
1) If you use an ATX12V 2x2 power connector, there are two yellow
wires for +12V. 2x6 amps is 12A. 144W total. If the Vcore converter
is 90% efficient, up to a 129.6W processor can be powered. There are
some Intel processors that have a 130W spec, so that is a comfortable
limit via the ATX12V 2x2 connector.
2) If the ATX12V 2x2 connector was not present, there is one yellow wire
on the main power connector. 12V * 6A = 72W input. At 90% efficiency,
the Vcore converter could power a 64.8W processor. That would be
barely enough for a Core2 Duo. Running from the 12V on the main
connector, would not be smart option.
3) It is also possible to do Vcore conversion from +5V. That is done
on some Asus Athlon motherboards (my A7N8X-E Deluxe has a two phase
converter, powered from +5V). With the four red wires on the ATX
20 pin power connector, there is a total of 24 amps available. You
cannot tap into all of that, due to "current hogging", but we'll
assume we can. 5V * 24A = 120W. At 90% Vcore conversion efficiency
(and the efficiency could well be different at 5V), you could draw
108W.
A P4 3.06GHz with Hyperthreading enabled, draws about 82W. If
the motherboard in question does not support Hyperthreading, then
less than 82W max would be drawn. Option (2) above is not good enough
to safely do the job. Option (3) and using +5V, can do it.
There was at least one P4 motherboard, that could not manage to run
a P4 3.06GHz processor, and had to stop at the 2.8GHz or so. So there
have been cases where the Vcore converter is not sufficient for every
FSB533 processor made.
I would think, if the motherboard is using the 5V rail, that a two phase
design would be pushed pretty hard. Notice though, that the powdered iron
cores are a bit larger than normal, and of the four MOSFETs, two are
larger ones. So maybe the thing is OK. The only thing I don't understand
about the two phase design (which could be a Richtek), is how they
manage to use so few capacitors. There must be a pretty substantial
ripple current, and the Vcore converter seems to not need many caps.
If there is any moral from this story, it would be:
Make sure the power supply has adequate 5V output - at least 20A
or more rating. Depending on the video card, the number of HDD,
you may want more than that. You want a so-called "AMD" power supply,
as at least a few AMD boards used 5V as well.
One way to check the design, is to feel the MOSFETs, the coils, and
capacitors around the processor, while running the Prime95 torture test.
If the components were running burning hot, then I would not assume
it would last a long time. If everything is cool to the touch, I
would be less worried about it. If the brand of caps used, are some
from the "bad cap" era, then I would be worried. I don't know my
capacitor brands by heart, and cannot tell you which brands are
the bad ones, but there is some information on the Internet about
it.
HTH,
Paul
