Re: Asrock dual motherboard power connectors

Palindr☻me wrote:
larry moe 'n curly wrote:

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:

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

Now look at this PSU:

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.

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

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,,, or
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

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. :(