"PJ" said:
I only have one 6800gt card in my system right now and it is hooked up
directly to the PSU. Does it hurt to have the molex power on the board
connected to the PSU as well or should I leave it disconnected until I get a
second card and run in SLI mode?
Thanks,
Paul
Generally speaking, additional power plugs can be connected
without causing a problem. It might not make the system any
more stable than it already is, but it should not hurt anything.
An issue to consider, is what kind of power supply is being
used. I can see at least three types making the rounds.
The PCP&C Turbocool, is an example of a pre ATX 2.0 spec
power supply. It has all of its 12V power coming from one
output winding. With this power supply, there would be no
concerns with using additional power plugs like the EZplug.
12V is 12V is 12V.
The next type of supply, is the ATX 2.0 type supply. It has
two outputs, called 12V1 and 12V2. You can get a spec here:
http://www.formfactors.org/devlist.asp?FFID=1&CatID=2
On the ATX 2.0 supply, the processor is powered by 12V2, and
the rest of the 12V loads (motherboard ATX 24 pin, disk drives)
run from 12V1. Again, in this case, it is safe to plug the
ATX 24 pin and a disk drive connector into the motherboard,
because they both run from 12V2 and are at the exact same
voltage. (Note that 12V1 and 12V2 are not at exactly the
same voltage, but neither are those two rails joined inside
the motherboard, and that is why the ATX 2.0 supply can work
in the first place, without burning anything.)
The third kind of power supply I've run into, is the
one with four 12V circuits. The Silverstone is a recent
addition to the Nvidia SLI certified power supply list.
The PCP&C turbocool 850W (just announced) also has this
feature. I don't know which standard defines this supply
class, whether it is SSI, GES or something else. (If
someone knows what standard is used for these, and has
a URL, I'd appeciate it if you would post it.)
http://www.silverstonetek.com/products-65zf.htm
http://www.linuxhardware.org/article.pl?sid=05/04/15/1742246&mode=thread
Here's how the SilverStone's 12V lines are divided, according
to the lunuxhardware review (as Silverstone didn't feel
we needed to know this info):
+12V1: CPU0 13A/18A
+12V2: CPU1, SATA, Motherboard 18A
+12V3: Motherboard, PCI-Express 16A
+12V4: Molex Connectors 8A/13A
Now, my first comment about the above info, is it doesn't look
right. The word "Motherboard" should only appear on
one line above, not two. That would be stupid.
Notice how in this case, that the Molex connectors are on
12V4, while the motherboard power is on 12V3. This is an
example of a power configuration where I would _not_ want
to connect the EZPlug. Since there are PCI Express power
connectors, this would be a great supply for dual PCI
Express video cards with their own 2x3 PCI Express power
plugs, as the EZPlug would not need to be connected.
The red warning LED will just have to light up your case
with its warm red glow.
The Enermax EG851 looks like it has quad 12V, as does the
new PCP&C Turbocool 850, the Silverstone product above, and
who knows what else. So far, I haven't seen enough detailed
info on any of these products, to see exactly how the power is
split between cable assemblies. If spending the big bucks
for one of these supplies, I would want a diagram labelled
with 12V1, 12V2, 12V3, 12V4 for each and every connector
on the supply. Otherwise, if different 12V outputs are
connected together, loop currents could start to flow.
I know some supplies have options to bridge rails like
these together, but I don't know if these new quad 12V
supplies have such an option or not.
The only company I can depend on for this info, is PCP&C.
They give good docs on their web site. The rest are hopeless
when it comes to product details. (Since the PCP&C 850W is
not shipping yet, the docs aren't on the site. I can't
wait to see if PCP&C properly label their four 12Vx
outputs.)
OK. I just downloaded the Enermax EG851 from here:
http://www.enermax.com.tw/download/EPS_12V_English.pdf
It looks like:
+12V1: CPU0 (one half of the 2x4 connector)
+12V2: CPU1 (other half of the 2x4 connector, also the 2x3 CPU connector)
+12V3: Motherboard
+12V4: ? Not stated. Maybe disk drive connectors ???
So, this would be another supply, where I would not want to
use the EZplug at the same time as the Motherboard plug is
there. That is because, then 12V3 and 12V4 end up connected
together. It would be really dandy if Enermax could write
a decent manual that told us where 12V4 goes...
Mixing a quad 12V power supply, with video cards having no
separate PCI Express power connectors, looks like a bad
thing, as then you really need the benefits of the EZplug.
In a case like that (if you had some 6600 class cards for
example), you would be much better off with a single 12V
output supply, or a dual 12V output supply like any ordinary
ATX 2.0 type supply.
Seeing as the quad 12V output supply is really overkill anyway,
avoiding it altogether is an even better option. In most
normal desktop circumstances, you aren't going to be able
to put any load on 12V2 anyway, so it amounts to only a
triple 12V output supply. And, since the EZPlug cannot
likely be used, the two video cards end up running off 12V3.
Which means any power left over on 12V4 cannot be harvested.
The quad 12V looks like it would be a good investment for that
dual opteron dual x16 PCI Express server board that was just
announced by Tyan.
Paul
