Re: New Pwr Supply W/O 6pin AUX connector for P4T-E
- From: "Bob" <bobnospam@xxxxxxxxx>
- Date: Fri, 4 Aug 2006 12:13:24 -0700
"Paul" <nospam@xxxxxxxxxx> wrote in message
news:nospam-0408060440410001@xxxxxxxxxxxxxxxx
In article <z6SdnUwGfpHjzk_ZnZ2dnUVZ_u-dnZ2d@xxxxxxxxxxx>, "Bob"http://www.xbitlabs.com/misc/picture/?src=/images/video/ati-powercons/t4.gif&1=1
<bobnospam@xxxxxxxxx> wrote:
I just got a 550W power supply which doesn't have the 6 pin AUX connector
for the connector on the P4T-E. It does have a 4 pin extension to the 20 pin
ATX connector that has a 3.3 V and Gnd line. From other postings I've found,
the AUX connector is for the display card. My display card is an ATI
all-in-wonder 9800 pro, which has a connector for a floppy-type power
cable. Can I operate without the AUX connection? Or should I make an
adapter to feed 3.3V and Gnd fron the 4 pin ATX extension to a 6 pin
AUX connector?
Bob
The P4T-E manual has the word "optional" after the connector
description in the manual. The P4T manual is missing the
word "optional". The P4T-E manual was issued a month after the
P4T manual
The AGP slot type is AGPPro, and if a true, power hogging, AGPPro
card was used, the AUXPWR would come in handy. There is slightly
less reason for AUXPWR with an ordinary AGP card. AGPPro cards
are rare (typical longish card, used for cad/cam or other OpenGL
type applications, many hot chips on board).
I tried looking for guidance again, but did not find any tales
of woe with respect to the use of the connector. Looking back
at one thread I participated in, it looks like one power supply
equipped with AUXPWR, actually had the connector on backwards,
and the resulting short prevented the motherboard from posting.
So even if you had one, using it isn't always a "bed of roses".
The part of the question I cannot answer, is how much +3.3V and
+5V is used by the rest of the motherboard. The main power
connector has (3) 3.3V pins, which can carry up to 18A. The
four 5V pins can carry up to 24A. The AUXPWR would allow
adding to the ampacity of the main power connector. But is the
total load on the motherboard such, that the 18A and 24A numbers
are exceeded ? There is no easy way to answer that, unless you
can find some data from someone who has measured the motherboard
in question.
For a 9800Pro (not AIW), there are measured current numbers here.
AIW should not be significantly different (unless the core and
memory clocks are different than the values shown):
There are five power rails on a card like that. The 5V and 12V are
the ones on the disk drive cable that plugs into the card. Xbitlabs
measured their card at two sets of frequency conditions (maybe they
overclocked the card), and got 5V@5A and 12V@xxxxx I've measured
that on my card, and got 5V@xxxx, so the numbers do look familiar.
Since this is the disk drive cable, the AUXPWR is not an issue
for that.
The 3.3V AGP, 5V AGP, 12V AGP are measured on the AGP slot, as
the current enters the card from the motherboard. The 3.3V is
measured at up to 5 amps in the Xbitlabs data, and much older
cards used to load that source of power up to the full allowed
6A. (One of the reasons a TNT family card black screened on me, on
an older motherboard.)
The 6A limit on the AGP slot 3.3V source can be seen in this
table copied from the AGP 3.0 spec. Your card can use 5A on that
rail when you are gaming or running 3DMark. Your other rails on
the AGP slot are insignificant.
**** AGP 3.0 current spec ****
Symbol Parameter Condition Min Max Units Notes (from AGP 3.0 spec)
Vddq1.5 I/O Supply Voltage IMAX = 2.0A 1.425 to 1.575 V 1, 2
VCC3.3 3.3V Power Supply IMAX = 6.0A 3.15 to 3.45 V
3.3VAUX 3.3V Auxiliary Supply IMAX = 0.375A 3.15 to 3.45 V
VCC5 5V Power Supply IMAX = 2.0A 4.75 to 5.25 V
VCC12 12V Power Supply IMAX = 1.0A 11.4 to 12.6 V
1. AGP3.0 requires no more than 1.0 amp average VDDQ current
through the connector.
2. A universal add-in card may need Vddq3.3 for AGP1.0 signaling.
********
Since your motherboard has an AGPPro slot, the AGPPro spec
would also apply to the AGP slot. The AUXPWR would help with
the additional allowed 3.3V consumption, so there might be
more reason to use it if an AGPPro video card was present.
AGPPro cards are not too common, and the cards are quite
large as a rule. I don't know how the motherboard would
provide 9.2A on +12V, if a card actually tried to draw that.
(But that fact does bother me, enough to suggest something
else worth checking.)
http://www.motherboards.org/files/techspecs/apro_r11a.pdf
VCC3.3 3.3V power Imax = 7.6A 3.15 to 3.45 V
VCC12 12V power Imax = 9.2A 10.2 to 12.6 V
Based on that AGPPro spec, one thing I would check with
my multimeter, is whether the ATX 2x2 12V power connector
has the 12V wire joined to the 12V wire on the main 20 pin
power connector or not. A reading of 0 ohms between those
two pins on the motherboard, means the processor power and
motherboard power are joined together. The ATX 2.0+ power
supply spec assumes they are separated. While some ATX 2.0+
supplies use a common source for the two outputs, strictly
speaking the spec for ATX 2.0+ says that the 12V1 and 12V2
are separate outputs. It would not be wise to short them
together - which is why I'd use my multimeter just to see
if Asus joined them together to try to support their "AGPpro"
video slot.
Just for fun, I just checked my P4B motherboard. It is
one of the boards with an EZPlug on it. And
the ATX 2x2 12V and the motherboard power are joined
together. Which means if I ever needed a power supply
replacement for the box in the future, it should not
be an ATX 2.0+ with 12V1/12V2 outputs. Since your
power supply has a 24 pin connector, it would be a
2.0+, and I'd want to check the P4T-E to see if
it has the 2x2 joined to the main power. Asus _may_
have done that, to help support an AGPPro video card, if
one was present.
Certainly, recently shipping Asus motherboards do not
join the 2x2 ATX12V to the main power connector 12V - this
is only a concern for motherboards of that particular
era, and I would want to check boards like P4T533,
P4T533-C, P4B, P4T, P4T-E to name a few.
In summary, I cannot really answer your original question.
I would need to know the base load of the motherboard, to
see whether any video card 3.3V consumption could possibly
be an issue. Maybe if the 12V turns out to be a problem,
you'll be searching for an older supply anyway ?
The word "optional" in the manual doesn't help me make
the decision, so I'd have to leave it to your discretion.
Using a clamp-on ammeter, wrapped around wires on the
main ATX power connector, while running 3DMark, would give
me some idea as to how valuable the AUXPWR connector is.
On the forums I looked at, the posters there treated it
as "use it if you got it", and I haven't seen any tales
of doom one way or another.
Sorry for the length of this posting :-)
Paul
No need to apologise. I really appreciate the detail
and references .you included. I will need to do some
more data gathering and calculations to determine my
final solution, but this is what I needed.
Bob
.
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