Asrock dual motherboard power connectors

S

SDR

I notice on the online manual for the 939 dual motherboard that there
are 2 power connectors:

4 pin ATX 12v power and 20 pin power connector.

Questions are:

Do I have to use the 4 pin connector (my power supply, 550W QTEC, does
not have such a connector

and what is this connector for please?
 
M

Michael Hawes

SDR said:
I notice on the online manual for the 939 dual motherboard that there
are 2 power connectors:

4 pin ATX 12v power and 20 pin power connector.

Questions are:

Do I have to use the 4 pin connector (my power supply, 550W QTEC, does
not have such a connector

and what is this connector for please?

Have you RTFM? Many PSUs with 24 pin connector, splits into 20 pin and 4
pin. What is spec of system QTEC does not have good reputation!
Mike.
 
T

Tweek

The four pin that splits off from a 20+4 pin PSU connector is not the same
as the ATX 12V connector which is a separate 4 pin connector usually near
the cpu. If the motherboard has it, it is required.
 
T

Tweek

Yes it is required. Get a different power supply. All new power supplies
have the atx 12v connector.
 
P

Paul

I notice on the online manual for the 939 dual motherboard that there
are 2 power connectors:

4 pin ATX 12v power and 20 pin power connector.

Questions are:

Do I have to use the 4 pin connector (my power supply, 550W QTEC, does
not have such a connector

and what is this connector for please?

The square connector provides power for the processor. If
it is not plugged in, the motherboard cannot POST or even
beep. You need both the 2x2 square connector with the 12 volts
on it, and the 20 pin main connector, for a working system.

This is not the same thing as a 20+4 power connector. There
are some 24 pin power supplies, where the 24 pin part can
be split into two pieces (20+4). The purpose of that splitting,
is to allow plugging just the 20 pin portion into the main
power connector, without having to worry about bumping into
any adjacent caps. Many motherboards will allow the 20 pin
section of a 24 pin connector to be plugged in without bumping
into adjacent components, so it isn't essential that the
24 pin portion splits into two pieces.

The 2x2 ATX12V square connector is a different animal. It
has two yellow wires, carrying +12V. It has two ground wires
which are black. That is how you can tell you have the correct
one.

I don't know if any adapters are made, to make a 2x2 if it is
missing. A disk drive molex connector has one yellow wire,
and you would need two separate disk drive cables, to donate
their yellow wire to an adapter, to get decent current. Your
power supply should be rated for a minimum of 12V@15A, to even
think about powering a system with a 2x2 ATX12V connector.

With your new motherboard, you should treat yourself to a new
power supply. Page 36 of this document, shows some diagrams
of the connectors on the new supplies.

http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf

To work out the rating for your new supply, you need to budget
for all the added components. Without a detailed list, it
is hard to be sure how much of a supply is needed. Generally,
the biggest concern is getting enough +12V, and that is
something that older supplies might not do. For example,
there was a Powmax a while back, that was a 500W supply, but
it only had 12V@10A, making the supply worthless for modern
computers having the square power connector.

Paul
 
S

SDR

The square connector provides power for the processor. If
it is not plugged in, the motherboard cannot POST or even
beep. You need both the 2x2 square connector with the 12 volts
on it, and the 20 pin main connector, for a working system.

Apologies guys - the connector is there but was tucked away as was not
required until now! It has 2 yellow and 2 black cables.

http://www.qtec.info/products/product.htm?artnr=13492

It does not give the output here or on the unit so cannot tell if it
is 15A or not.

I am currently using Abit NF7-S motherboard which has this connector
but I have not connected it - the system still works. Could it be that
I am using AMD XP 2500+ which does not need it?

I am planning to upgrade to XP3700+ which may need it.
 
L

larry moe 'n curly

I am currently using Abit NF7-S motherboard which has this connector
but I have not connected it - the system still works. Could it be that
I am using AMD XP 2500+ which does not need it?

It's not the CPU but the design of the mobo. Apparently yours has the
+12V from the square 4-pin ATX12V connector and the +12V from the
yellow wire on the 20-pin connector tied together on the mobo, so it
works even without the ATX12V connector.
A couple of years ago I believe I had a PC Chips (ECS) Socket A mobo
where those +12V connections were kept separate, so if the ATX12V
connector was left unplugged, the CPU wouldn't run at all. I verified
this by measuring the cuirrent through the lone yellow wire on the
20-pin connector, and it was zero amps. However, just because you can
run a CPU without the ATX12V connector doesn't mean you should because
that single yellow wire's pin can carry only about 6-8 amps before
overheating (can melt the plastic off the connector and wiring), so
don't operate the mobo that way if you have a fast, power-hungry CPU.
I am planning to upgrade to XP3700+ which may need it.

Whether you upgrade or not, get rid of that Q-tec PSU and buy something
of high quality. A good 400-450W PSU can probably handle it and will
have more actual power capacity than your 550W Q-tec. Look for
Fortron-Source (most model numbers start with "FSP"), Zippy, Delta,
Antec, Enhance, Seasonic, or Lite-On.

Look at the insides of the Q-tec:
http://static.flickr.com/41/79709280_e68a4d0001_o.jpg

Notice that the big capacitors in the lower left are each rated for
only 470uF.

Now look at this PSU:
http://static.flickr.com/38/75117436_1de7a3142d.jpg

It's much more substantial, despite being rated for only 300W, and the
big capacitors are 70% larger.
 
G

Guest

larry said:
It's not the CPU but the design of the mobo. Apparently yours has the
+12V from the square 4-pin ATX12V connector and the +12V from the
yellow wire on the 20-pin connector tied together on the mobo, so it
works even without the ATX12V connector.
A couple of years ago I believe I had a PC Chips (ECS) Socket A mobo
where those +12V connections were kept separate, so if the ATX12V
connector was left unplugged, the CPU wouldn't run at all. I verified
this by measuring the cuirrent through the lone yellow wire on the
20-pin connector, and it was zero amps. However, just because you can
run a CPU without the ATX12V connector doesn't mean you should because
that single yellow wire's pin can carry only about 6-8 amps before
overheating (can melt the plastic off the connector and wiring), so
don't operate the mobo that way if you have a fast, power-hungry CPU.




Whether you upgrade or not, get rid of that Q-tec PSU and buy something
of high quality. A good 400-450W PSU can probably handle it and will
have more actual power capacity than your 550W Q-tec. Look for
Fortron-Source (most model numbers start with "FSP"), Zippy, Delta,
Antec, Enhance, Seasonic, or Lite-On.

Look at the insides of the Q-tec:
http://static.flickr.com/41/79709280_e68a4d0001_o.jpg

Notice that the big capacitors in the lower left are each rated for
only 470uF.

Now look at this PSU:
http://static.flickr.com/38/75117436_1de7a3142d.jpg

It's much more substantial, despite being rated for only 300W, and the
big capacitors are 70% larger.
I would suggest that the quality of the heatsink arrangements is a
better indicator for those unfamiliar with electronic components.

IME, cheap supplies, typified by bent pieces of aluminium sheet as heat
sinks, run their primary active devices at a much higher temperature.
Any loss in active cooling, say by a build up of dust on heatsinks or
fan blades, high ambient air temperatures (due to the room temperature,
or other dissipation in the case) takes these active devices out of
their SOAR. Thus, even if the supply, when new, meets specification - it
will age and fail prematurely in normal use.

The extruded aluminium heatsinks, found in quality supplies, have a free
air thermal resistance low enough to require very little active cooling.
They can run happily at much lower fan speeds and hence lower noise.

Looking at the components, the choice of the component used for the
energy recovery diodes is an excellent indicator. Cheap supplies use
cheap "general purpose" switching diodes which dissipate far more than
the much more expensive very high speed diodes used in quality supplies.
Whilst this doesn't matter much at light loading, at heavy loading this
dumps a lot of unnecessary heat into the secondary heatsink.

Finally, the presence of extra components not essential to the normal
operation of the unit are a good indication of what to expect from the
supply. Crowbar circuitry on the outputs, anti-tracking conformal
coating on the pcb, dual inrush protection, etc all make for a power
supply that will do its job for many years and, ultimately, fail safe if
it does fail.

All that costs extra. The added costs of the extra almost invariably
being more than the total cost of *all* the bits needed to make a cheap
supply.

Unfortuantely, some buyers seem more impressed by multiple fans, gold
plated cases, pretty lights, etc than plain old good design practice,
hidden away inside.
 
L

larry moe 'n curly

Palindr☻me said:
larry moe 'n curly wrote:
I would suggest that the quality of the heatsink arrangements is a
better indicator for those unfamiliar with electronic components.

IME, cheap supplies, typified by bent pieces of aluminium sheet as heat
sinks, run their primary active devices at a much higher temperature.
Any loss in active cooling, say by a build up of dust on heatsinks or
fan blades, high ambient air temperatures (due to the room temperature,
or other dissipation in the case) takes these active devices out of
their SOAR. Thus, even if the supply, when new, meets specification - it
will age and fail prematurely in normal use.

The extruded aluminium heatsinks, found in quality supplies, have a free
air thermal resistance low enough to require very little active cooling.
They can run happily at much lower fan speeds and hence lower noise.

What about PSUs with 120mm fans? Many of them have thin heatsinks, as
this 430W Seasonic does:


www.slcentral.com/dual-12v-psu-shootout/Seasonic/inside-1.jpg

Another well-regarded brand, Fortron, has at least one 120mm model
where the heatsinks are just flat pieces of aluminum (3 heatsinks
instead of the usual 2).
Looking at the components, the choice of the component used for the
energy recovery diodes is an excellent indicator. Cheap supplies use
cheap "general purpose" switching diodes which dissipate far more than
the much more expensive very high speed diodes used in quality supplies.
Whilst this doesn't matter much at light loading, at heavy loading this
dumps a lot of unnecessary heat into the secondary heatsink.

I believe a photo of that was recently posted in a forum at
Overclockers.com, Overclockers.com.au, HardOCP.com, or BadCaps.net.
But how is the average person supposed to be able to notice it?
Because unlike big things, like heatsinks and high voltage caps, those
things are hard to see without opening the PSU, and even if they are
opened, the markings can be hard to decipher or even read because the
components are in a tight space. I've never seen high speed diodes
replaced by general purpose diodes in an ATX PSU, but I did see that in
an AT PSU made with steel heatsinks.
Finally, the presence of extra components not essential to the normal
operation of the unit are a good indication of what to expect from the
supply. Crowbar circuitry on the outputs, anti-tracking conformal
coating on the pcb, dual inrush protection, etc all make for a power
supply that will do its job for many years and, ultimately, fail safe if
it does fail.

Do any ATX PSUs have crowbars? The only thing I've seen is overvoltage
detection circuitry that shuts down the PSU controller chip, which may
not be enough to prevent any voltage surge from getting out.

I'd like to know what ATX PSUs are designed to shut down if they get
too hot. I have some Fortrons with a missing second thermistor on the
low voltage side that may be for that, but the circuit doesn't make any
sense to me. And newer Antec SmartPowers and TruePowers have a second
diode, but when I shorted across it, nothing happened. I've added
overtemperature shutdown to some PSUs, but because I don't know that
much, in some PSUs it works only on the high voltage side.

What is dual inrush protection, the use of two thermistors on the AC
side? If so, I've seen it in only one ATX PSU, the 300W one in the
second picture above.
All that costs extra. The added costs of the extra almost invariably
being more than the total cost of *all* the bits needed to make a cheap
supply.

Unfortuantely, some buyers seem more impressed by multiple fans, gold
plated cases, pretty lights, etc than plain old good design practice,
hidden away inside.

It's better to look good than to feel good. :(
 
G

Guest

larry said:
What about PSUs with 120mm fans? Many of them have thin heatsinks, as
this 430W Seasonic does:


www.slcentral.com/dual-12v-psu-shootout/Seasonic/inside-1.jpg

Another well-regarded brand, Fortron, has at least one 120mm model
where the heatsinks are just flat pieces of aluminum (3 heatsinks
instead of the usual 2).

LOL. Well, OK, change it to look for a *lot* of heatsink aluminium, not
necessarily extruded. A thick chunk of sheet aluminium can rival an
extrusion in terms of free air thermal resistance. But I must admit to
liking extrusions - which do tend to have more metal nearer to the
active devices and thus do result in lower chip temperatures.
I believe a photo of that was recently posted in a forum at
Overclockers.com, Overclockers.com.au, HardOCP.com, or BadCaps.net.
But how is the average person supposed to be able to notice it?
Because unlike big things, like heatsinks and high voltage caps, those
things are hard to see without opening the PSU, and even if they are
opened, the markings can be hard to decipher or even read because the
components are in a tight space. I've never seen high speed diodes
replaced by general purpose diodes in an ATX PSU, but I did see that in
an AT PSU made with steel heatsinks.

I think even the cheapest supplies use switching diodes - but general
purpose switching diodes not designed specifically for smpsu.
Do any ATX PSUs have crowbars? The only thing I've seen is overvoltage
detection circuitry that shuts down the PSU controller chip, which may
not be enough to prevent any voltage surge from getting out.

Here is one that mentions that it does:
http://www.jenlogix.co.nz/products/ace-828.htm

I like ThermalTake supplies which, IIRC, do have a row of fast SCRs at
the output rails for crowbar. But I mostly see the insides of server
power supplies -which cost enough to be worth repairing when they fail.
I'd like to know what ATX PSUs are designed to shut down if they get
too hot. I have some Fortrons with a missing second thermistor on the
low voltage side that may be for that, but the circuit doesn't make any
sense to me. And newer Antec SmartPowers and TruePowers have a second
diode, but when I shorted across it, nothing happened. I've added
overtemperature shutdown to some PSUs, but because I don't know that
much, in some PSUs it works only on the high voltage side.

What is dual inrush protection, the use of two thermistors on the AC
side? If so, I've seen it in only one ATX PSU, the 300W one in the
second picture above.

Yep, as you say, dual inrush uses two devices in series, one of which is
shorted out by a set of time-delay relay contacts when the supply is
powered up. If the mains is briefly interrupted, this second device will
limit the inrush current as it is cold - unlike the primary device.
 
L

larry moe 'n curly

Palindr☻me said:
LOL. Well, OK, change it to look for a *lot* of heatsink aluminium, not
necessarily extruded. A thick chunk of sheet aluminium can rival an
extrusion in terms of free air thermal resistance. But I must admit to
liking extrusions - which do tend to have more metal nearer to the
active devices and thus do result in lower chip temperatures.

Here's what LinuxGuru at www.BadCaps.net found regarding undersized
components in a Deer PSU:

"PEC SB1040CT dual 10A Schottky-Barrier Rectifier on the +5v rail - one
of the two diodes had shorted out. BTW, +5v has a (fake) rating of 30A
on this unit; going by the rating on the rectifier, it shouldn't be
more than 20A continuous,...

"The 3.3v rail has a similar 10A rectifier, and the ones on the +12v
rail are 3A FR302 rectifiers. That gives us a maximum power rating of
20A x 5V + 20A x 3.3V + 6A x 12V + 2A x 5V (+5Vsb) = 100 + 66 + 72 + 10
= 248 W, and I'm being very generous on the combined rating of the +5v
and +3.3v rails."
I think even the cheapest supplies use switching diodes - but general
purpose switching diodes not designed specifically for smpsu.

I've found non-Schottky diodes for the +12V rail in some quality PSUs,
like the STPR16 (rated 200V) in a Delta.
 

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