P
Paul
"dino" said:
That passes the ampacity problem, to where the 20 pin adapter
meets the 20 pin ATX power supply. The current flowing through the
two pins on the 24 pin end of the adapter, is flowing through a
single pin where the 20 pin ends meet. You have transferred the
overheat problem to the 20 pin end. Using the adapter hasn't
solved anything, other than being aesthetically pleasing.
For many computer builds, the motherboard load through the
main power connector, on the +12V, does not exceed 6 amps.
While this is "the right way" to build them, it frequently
isn't necessary. The two pins for +12V on the 24 pin
connector can carry up to a total of 12 amps into the
motherboard before they get hot.
ATX_PSU ------------24 pin ----- 24 pin motherboard
^
|
2 pins carries +12V current---+
You can plug a 20 pin connector directly to the 24 pin mobo.
For example, if you had a 6600GT (which has no PCIe power
connector at the end of the card) and three fans, the
4.5 amps drawn while gaming, are easily provided by the 6 amp
limit of the single pin.
ATX_PSU ------------20 pin ----- 24 pin motherboard
^
|
1 pin carries +12V current---+
Using a 20 pin to 24 pin adapter, still forces the current
through the one pin. That pin is where the 20 pin ATX
supply meets the 20_to_24 pin adapter. This adapter
solves nothing, and in fact only adds voltage drop caused
by the increased length of wire. While it looks pretty,
it isn't actually solving any problem. If there was an
overloading problem, the plastic on the ATX PSU end could
be damaged, meaning you might have to replace the power
supply. Which I suppose is marginally better than the
case above, where both the PSU and motherboard plastics
melt. In any case, this is not doing your customers
any good - either you do the math and know the config is
adequately served by the 20 pin supply, connected directly,
or use the 24 pin supply if you think that somehow, the
amps to the motherboard, are going above 6 amps.
ATX_PSU ---20 pin --- 20pin_to_24_pin ---- 24 pin motherboard
^ ^
| |
Only 1 pin here, so Two pins here
this is the hot spot so not as hot
It is pretty easy to see, for a non-SLI board, that
connecting the 20 pin ATX to the 24 pin motherboard will
be OK. But there are components entering the marketplace,
that can negate that easy answer. For example, Matrox now
makes a PCI Express x1 video card, which can be plugged into
any PCI Express slot. Which means a non-SLI motherboard can now
have multiple video cards plugged in, with who knows how much
PCI Express power consumption. Depending on whether the Matrox
product uses +12V or not, could mean that more than 6 amps are
required (i.e. 4 amps for a 6600GT + ??? amps for the Matrox),
and then you need to use a real 24 pin power supply.
That determination becomes more challenging with SLI
systems. If I was crazy, and I SLI a couple of 6600GT
(with no PCIe power connector on the end of the cards), then
8 amps come from the motherboard. If the motherboard has
an EZPlug (a molex connector next to the video cards), then
that molex, plus the 20 pin, is still enough for the job.
However, if the SLI motherboard being used did not have any
auxiliary assistance like that Molex, then a real 24 pin
power supply should definitely be used. If you use your
20_to_24 pin adapter for that silly example of a couple
6600GT PCIe cards, then the adapter will melt where it meets
the 20 pin power supply.
If you cannot work out the expected current, or at least
have not instructed your customer how to do the calculation,
so they know when to replace the supply, you are doing them
a disservice by using that adapter. Sticking a real 24 pin
power supply in there, is an easy way to make friends, even if
it costs a few more bucks. You can even explain to your
customer, why you are doing it - for their own good.
Paul