"KC Computers" said:
The 20-pin connector will work fine with that board
without an adapter. It's not recommended if you
will be using a high powered performance video
card, however.
And that is due to the 20 pin connector having only one +12V
pin, while the 24 pin connector has two +12V pins. A single
pin is rated for 6 amps, before it gets hot and potentially
melts the plastic around the pin. A high end video card could
draw 4.5A, and your fan headers draws a bit too. And depending on
whatever else Asus loads onto the +12V, there could be a slight
contribution as well. (Xbitlabs has articles, where they measure
video card current consumption, so you can sometimes find
numbers there.)
If you use some kind of adapter product, that converts a
20 pin to 24 pin, that really wouldn't help, as where the
20 pin connector plugs into the 20 to 24 pin adapter, the
same 6 amp limit would exist. (That means, there is still
a potential to melt the plastic, but on the power supply end of
the power chain.) If, on the other hand, the adapter consisted
of a disk drive connector plus a 20 pin ATX connector on the
source side, and a 24 pin connector on the destinaton side, then
both ends of the adapter have two +12V pins, and then nothing
can get damaged. (But I haven't seen any adapters designed
that way.)
old 20 pin cable 24 pin mobo
x (pin not fed)
PSU ----------------------------------x this pin fed
^
|
Potential hot spot will be here ---+
if more than 6 amps flows into mobo
20 pin to 24 pin adapter
+------------------x 24 pin mobo
PSU --- 20 pin ------------+------------------x two 12V pins
^
|
+--- Potential hot spot will be here as
all current flows through one pin
If I was designing an adapter, I'd want to combine a 4 pin
disk drive connector plus a 20 pin power on the left, to
feed a 24 pin power connector on the mobo on the right. I
haven't seen one for sale like this.
PSU --- 4 pin DD conn --+
+---+------------------x 24 pin mobo
PSU --- 20 pin -------------+------------------x two 12V pins
EATXPWR
Pin Signal Pin Signal
1 +3.3 VDC Orange 13 +3.3 VDC Orange
2 +3.3 VDC Orange 14 -12 VDC Blue
3 COM Black 15 COM Black
4 +5 VDC Red 16 PS_ON Green
5 COM Black 17 COM Black
6 +5 VDC Red 18 COM Black
7 COM Black 19 COM Black
8 PWR OK Gray 20 -5 V
9 5 VSB Purple 21 +5 VDC Red
10 +12V2 Yellow 22 +5 VDC Red
11 +12V2 Yellow 23 +5 VDC Red
12 +3.3 VDC Orange 24 COM Black
Pins 11,12,23,24 are the extra pins added to the 24 pin
connector, over and above the 20 pin connector. Pin 1 on
both connectors lines up. To make an adapter, a source
of a single +12V, a +5V pin, a +3.3V pin and a ground
return pin are needed. A disk drive connector can give
+12V, +5V, GND. The old style 1x6 Aux power connector
could be used to donate +3.3V. Only the +12V is immediately
critical, followed by the ground pin on pin 24. The +3.3 and
+5V likely have enough current already.
You could craft a good adapter, by taking a 20 pin to 24 pin
adapter, and a disk drive Y connector. That should give enough
materials to make an adapter that has two +12V pins on
the left, to feed the two +12V pins on the 24 pin connector.
Before spending the time on a project like that, it is best to
chase down the power consumption numbers for your video card
and for the fans fed off the same +12V supply. If the video card
happened to have a separate power connector, so much the better,
as that would really reduce the risk to the mobo power connector.
Is this likely to be a problem ? My guess would be not
too likely, unless the video card is really sensitive to
the quality of the +12V. (So, maybe it won't burn, but maybe
the voltage on the video card could be on the low side.) Asus
put an Ezplug on the A8N-SLI and I really like that concept,
as it would remove the risk entirely when using a 20 pin power
supply.
Something else I noticed, when reading the manual (and this
is for you dudes who buy stuff without reading the manual
first) - while the A8N-E mobo has a PCI-E x4 connector on
it, the tech writers use weasel words when they say
"1GB/sec _total bandwidth_". How I interpret that, is
512MB/sec up and 512MB/sec down, which means the slot only
has x2 wiring placed on an x4 connector.(Note that the weasels
couldn't just says "its a x2 slot - get over it".) Just in case
you have a x4 disk controller board that expects a full x4
rate, or that you care about such things.
I wondered about that connector when I first saw the board
specs, because it seemed like too much bandwidth for the
typical bus bridges used on desktop chipsets.
A sweet alternative, would be to use an SLI board, stick a
video card in one slot, in x8 mode, plus a disk controller
card in the second video slot (x8 mode, but only uses
x4 mode bandwidth). But I still haven't read whether there
are any restrictions on video slots being usable for
generic PCI-E plugin cards, so i don't know if this is a
viable option or not. It should work, but Nvidia controls
the chipset drivers...
Paul
