HotJuly said:
About three weeks ago my power supply went out on my Asus mobo (p4s533 or
something like that). The asus mobo had a 4-pin cpu power connector from the
psu going to it. Well I had a spare psu that had no such 4 pin cpu connector
but I put it in anyway and the computer ran just fine. It's been running
fine for almost a month. Yesterday I turned comp on and got the "no signal"
display on the monitor, which suggests a cpu or psu problem to me. The mobo
does not beep when powered on either. No, nothing wrong with video card or
hdd. I need to know what, if any, damage could had been caused to the cpu by
not running the 4 pin power connector to it? Seems to me if there was a
problem, it just wouldnt boot, sort of like now
But it did run fine for
three weeks without the connector, so I don't get it.
A link to the pic of the 4 pin connector is below if you need to know for
sure what I am talking about.
http://i10.tinypic.com/29kwduq.jpg
Whether you've caused a problem or not, depends on how much power the
processor uses. The processorfinder.intel.com site can help you
determine how much power is used at maximum. I just assumed a certain
processor below, for the sake of an example.
First of all, I should explain what should have happened. On modern
boards, the ATX12V 2x2 is not shared with the main power connector.
Each connector has 12V wires, but they go to different things.
If you don't plug the connector to the ATX12V on a modern motherboard,
the computer cannot boot because the processor wouldn't have power.
Why this is important, has to do with the newest power supplies.
They are called "dual rail", meaning the ATX12V 2x2 connector is
powered by "12V2" rail. And the main power connector is powered
by "12V1" rail.
ATX12V 2x2 yellow wire X ---------------------------> to processor
X ---------------------------> Vcore circuit
Main 20 pin yellow wire X --------------------------> to fan headers,
to card slots,
to RS232 chips
A few early P4 boards, hooked the two sets of wires together.
This is bad, if you happen to connect a dual rail supply, where
the rails are truly independent. If you use a single rail supply,
then the single rail supply would not care if it was faced with
this:
(some original P4 S478 boards)
ATX12V 2x2 yellow wire X --------------+---------------> to processor
X --------------+---------------> Vcore circuit
|
Main 20 pin yellow wire X -------------+---------------> to fan headers,
(wired to card slots,
together) to RS232 chips
I've read some cases where recently purchased Biostar boards
are still doing this. AFAIK, most other brands keep the
wires separate, so if ATX12V is not connected, the computer
won't POST.
Now to how damage can occur. Let's say you don't connect the
ATX12V, and the motherboard design has made the mistake of joining
all the 12V wiring together. This is how it would look.
+------------> to processor
+------------> Vcore circuit
|
Main 20 pin yellow wire X -------------+------------> to fan headers,
(wired to card slots,
together) to RS232 chips
That single yellow wire and pin on the 20 pin connector, is
rated for 6 amps. Say we had an 89W processor. I assume the
Vcore converter circuit (the MOSFETs, coils, and capacitors
next to the processor socket) is about 90% efficient. That
means the input to Vcore is 89W/0.90 = 98.9W. Dividing that
by 12V, gives 8.24 amps. The fans in the computer, might
be drawing another 0.5 amps from the fan headers. The total
is close to 9 amps, just for those two loads, flowing through
the single wire on the main connector. The single pin on
the 20 pin connector, is rated for 6 amps.
That can cause the connector pin to get hot and oxidize. The
finish on the pin may no longer be shiny. The pin will
have more resistance, and tend to get hotter with passing
time. In some cases, it gets so hot, the nylon connector
shell melts near the pin.
So, I'd have a look at the motherboard and PSU connectors, to
see if the single 12V pin is damaged at all.
This power supply is an example of a single rail supply,
suitable for any board where you suspect the "wiring together"
problem, like the Biostar boards. Since your symptoms suggest
your P4S533 is wired like that, then I'd go for one of these
as a replacement supply.
+3.3V@32A, +5V@32A, +12V@26A, -5V@1A, -12V@1A,
[email protected]
http://www.newegg.com/Product/Product.asp?Item=N82E16817103455
There is no big secret to that supply. It is an "ATX 1.3" standard
supply. More modern dual rail supplies are "ATX 2.0+" standard.
So if you don't like the Enermax above, you'd search for another
brand offering an ATX 1.3 standard.
Also, on that supply above, the main connector is listed as "20+4".
Don't panic. The 24 pin connector comes apart into two pieces.
The optional 4 pin section on the end is removable. You can see
a "rib" in the plastic, where the 4 pin meets the 20 pin, and
that is where they slide apart.
Also, once the 4 pin optional section is detached, don't mix it
up with the ATX12V 2x2 connector. The ATX12V that goes to the
processor, has two yellow wires and two black wires, for +12V
and GND respectively. The 4 pin optional section, which you
won't be using, has four different colored wires.
If you plug in that Enermax supply, connect the 20 pin and
the ATX12V 2x2, and the computer does not POST - it could be
either that the motherboard pin is damaged on the 20 pin
main connector on the motherboard, or something got fried
inside the motherboard PCB. But chances are, it'll return to
life once you connect a real supply to it.
HTH,
Paul
