Ihatefishsauce wrote:


Thanks Paul....you seem to be one of the heavies here. I read around
before joining. Thanks for the rescue. Seems straightforward enough.
I am just incensed now that I spent $12.99 + shipping for the power
supply converter cable. If you don't really need one......then why
the h***K do they make one and market it as if you really do need
one? Just to make some$$$$?

thanks again!


That is a good question. The 20 pin to 24 pin adapter, moves the
"burn point" to where the adapter meets the power supply. At that
point, the current is still flowing through the one 12V pin on
the 20 pin connector. In that sense, the adapter doesn't solve
any problems. What it does do, is if a high current situation
were to arise, the PSU connector would be damaged, the
20 pin end of the adapter would be damaged, but the motherboard
would be saved.

The single pin on the 20 pin connector, is rated at 6 amps. That
12V wire, is connected to any adapter slot that needs it, as well
as the fan headers. In the current day, PCI Express x16 video cards,
would be the primary load. The highest number I've seen measured,
for the x16 slot, is 4.35A from 12V. The fan headers might have an
average load of, say, 0.5A. The other slots, might have a connection
to the 12V rail, but probably aren't using it. I would be most
concerned, if a lot of add-in cards started showing up, which
loaded down the 12V wire.

Based on the previous paragraph, for most users, no matter what
kind of single PCI Express video card they use, they should be
safe with a 20 pin power connector. If the motherboard is an
SLI or Crossfire config, and the user has two video cards, at
that point it is time to say, no more 20 pin supply. At that point,
it would be wise to invest in a 24 pin supply.

Some motherboards have a 1x4 Molex on the motherboard. For
SLI or Crossfile, that connector can help, and can delay the
need for the 24 pin connector. The Molex is good for up to about
8 amps (depends on the gauge of wire used), meaning a 20 pin
power connector, plus a 1x4 connected to the motherboard, gives
room for up to 14 amps to flow.

Getting back to the adapter again, another disadvantage of the
adapter, has to do with the remote sense function on the power
supply. You might notice (in those specs I quoted), that there
is provision for two wires to be connected to one of the 3.3V
pins on the PSU. The thinner of the two wires, is a sense wire.
Its job, is to take a sample of the voltage, right at what is
considered to be, the "load". When you use an adapter, the voltage
drop in the adapter is no longer compensated by the remote
sense function. That is because the thin sense wire, is not
at the load any more, and is now "half way along the cable",
The voltage error is small, but is another tiny issue with
the use of an adapter.

They make the adapters to fill a need :-) Customers want
the adapters - companies make them. Sort of like hood
ornaments for cars.

Paul