Sign in with
Sign up | Sign in
Your question

Power Supply for Asus P5AD2 Motherboard?

Last response: in Motherboards
Share
Anonymous
a b ) Power supply
a b V Motherboard
September 19, 2004 7:34:05 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

The Asus P5AD2 Deluxe motherboard uses a 24-pin ATX power connector. There
are very few power supplies available that support this new ATX 12V Version
2.0 format. Is it safe to use a standard 20-pin power supply with this
motherboard? The manual is somewhat vague in regard to this issue, and I'm
looking for a definitive answer.

Thanks.
Anonymous
a b ) Power supply
a b V Motherboard
September 19, 2004 1:16:27 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Ken" <___ken3@telia.com> wrote in message
news:shcqk097ru26m4vvri28jsa2tp5g793j7p@4ax.com...
> http://www.antec-inc.com/ec/productDetails.php?ProdID=0...
>
> http://www.antec-inc.com/ec/productDetails.php?ProdID=0...

Thanks, Ken. I do know that they exist, and I was actually looking at the
Antec NeoPower, but I already own a 500W power supply that I like better,
and I'd prefer to use it rather than purchasing a new one, if possible. The
motherboard manual says that use of a 20-pin power supply is "not
recommended," though it can be done. Every review of the board that I've
read, though, says that using a standard power supply works fine, and that
the board is fully backward-compatible with the 20-pin power supplies. I'm
just trying to ascertain whether it's a good idea or not. I need the new
machine I'm building with this board to be reliable.
Related resources
September 19, 2004 2:14:46 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <N673d.6533$mb6.4923@newsread3.news.atl.earthlink.net>, "X
Offender" <nospamplease@earthlink.net> wrote:

> The Asus P5AD2 Deluxe motherboard uses a 24-pin ATX power connector. There
> are very few power supplies available that support this new ATX 12V Version
> 2.0 format. Is it safe to use a standard 20-pin power supply with this
> motherboard? The manual is somewhat vague in regard to this issue, and I'm
> looking for a definitive answer.
>
> Thanks.

The difference between connectors is in the ability to deliver current
to the load, the ampere capacity. The Minifit Jr connector is rated
for 6 amps per pin, and that figure is used to derive the following.

If you compare the 20 pin connector to the 24 they show in the
manual, the 24 has an extra +3.3, +5.0, +12, and GND pin. Pin 1
of the 24 pin connector, I think, is in the lower left hand corner.
Pin 1 of the 20 pin connector should plug in there. The top four
pins are the "extra" ones.

The extra pins would be worth 6 amps a piece. For +3.3V, it boosts
the limit from 18amps to 24amps. For +5.0V, it boosts the limit from
24amps to 30amps. For +12V, it boosts the limit from 6amps to
12amps (from the ATX connector, plus it can draw another 2x8=16amps
from the 2x2 connector). Those are the amounts of current that
can flow from the PSU to the motherboard, without damaging the ATX
power connector. Generally, the 2x2 connector is used only for the
processor, whereas the single +12V pin on the ATX 20 pin is used
to handle fan headers etc.

On the load side, the new motherboards aren't much different from
older motherboards. PCI Express is a bit different, and especially
the video card slot could place new demands on things.

I found an Intel slide set, and it lists the PCI-E video card slot
power limits. These limits are based on the PCI-E connector and
how much current can flow through the pins of the video card.

+12V 5.5A (max)
+3.3V 3.0A (max)
3.3Vaux 0.38A (max) [ likely regulated down from +5VSB ]
(Card may draw a total of 75W. Ordinary 1x PCI-E cards are allowed
up to 25W.)

If you had a video card that draws as much power as it can from
+12V via the edge connector of the video card, and you used the ATX
20 pin connector, the card can draw 5.5A and the single +12V pin
on the ATX 20 pin is rated for 6A. Asus usually powers the fan
headers from this +12V pin, so if three fans drew an amp or so,
the total draw would be 6.5A.

PSU --+---- single +12V pin ------+-----+-----+-----+
| MiniFit Jr 6A per | | | |
| pin limit Fan Fan Fan PCI-E Video
| 0.33A 0.33A 0.33A 5.5A
|
2x2 +---> Up to 16A for Vcore.
12V | 115W Prescott draws
conn. +---> (115W/12V)*(1/0.9)=10.6A

If you buy a video card, and it uses an aux connector on one corner
of the video card, that connector will provide the extra current the
card requires. But, the trouble is, the PCI Express video cards I've
looked at so far, don't have an auxiliary connector for power,
which means it is all coming through the edge card.

This article measures power consumption of current generation cards.
This is for an AGP card, but the PCI-e will just use a hot bridge
chip to get to PCI-e country. The 6800 is measured at 72W at full
load.

http://www.xbitlabs.com/articles/video/display/ati-vs-n...

The current measurement is here. 12V@4.62A. With the three fans on
the same +12V pin, the total current of 5.62A is just under the 6A
limit. You could help things a bit by running the fans off Molex
disk drive connectors, and just route the tacho signal to the mobo
fan headers.

http://www.xbitlabs.com/articles/video/display/ati-vs-n...
http://www.xbitlabs.com/misc/picture/?src=/images/video...

Any 1x PCI-E cards that you plug into the other slots, will
be drawing next to no power (like 1W for a typical function), so
they don't even enter into the equation. It would take a complex
function, like say an embedded computer on a board, to draw
enough power to be a concern. Any PCI-e card consisting of a
single chip on board (Ethernet, cheap sound card, Firewire card,
USB card) will draw around 1W or less.

Here is an example of a PCI Express video card that has two
Molex drive connectors for power. A card like this means you
can use the ATX 20 pin without worrying. It means the designer
is running the switchers from the Molex connectors.

http://www.tweakers.net/nieuws/29357

But the other PCI Express video cards I've looked at, don't use
an Aux connector, so the 5.62A of 6A test case above remains as
the closest to heating up the single +12V pin on an ATX 20 pin
connector.

In the description above, notice how easy it is to draw more
than the 12V@15A recommendation for a basic system. At 10.6A
for high end processor, 4.62A video, 1A fans, 0.5A per drive,
18A is the starting number, and a couple more amps for margin
would help. Since the processor and disk drive currents are
flowing through other pins and cables from the PSU, there is
no danger from those loads.

It is difficult to do a similar analysis for the other supplies,
except to use an Intel motherboard power spec. This spec is
for the Intel D925XCV, and table 37 is on page 85.

ftp://download.intel.com/design/motherbd/cv/C6859701.pd...

Table 37. DC Loading Characteristics
DC Current at:
Mode DC Power +3.3V +5V +12V -12V +5VSB
Minimum loading 200.00W 3.30A 10.00A 9.00A 0.03A 0.80A
Maximum loading 300.00W 6.00A 14.00A 16.00A 0.10A 1.40A

The +3.3V and +5V currents are low, compared to the 18A
and 24A limits of the ATX 20 pin connector, so those
shouldn't be a problem. The Intel manual says part of that
+5V allocation, is to power imaginary PCI-e cards drawing
an average of 2A per slot.

So, under some circumstances, the +12V pin on the ATX 20 pin
connector is running close to its limit, and that is
where the "you can do it, but not recommended" comes from.

HTH,
Paul
Anonymous
a b ) Power supply
a b V Motherboard
September 20, 2004 12:16:55 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Paul" <nospam@needed.com> wrote in message
news:nospam-1909041015310001@192.168.1.177...
> ...
>
> HTH,
> Paul

Wow. Thank you so much for taking the time to write such a clear and
detailed explanation. That helps a great deal, as I know next to nothing
about these power issues.

The video card I'll be using is the PCI Express Gigabyte Radeon X600 XT
(model # GV-RX60X128V). It does not utilize an auxiliary power connector. I
have no idea what kind of power consumption to expect from this card. I'll
also be running two 120 mm case fans. I won't be installing any other cards,
as this motherboard has virtually everything built in (I'll be using onboard
sound and networking).

The specs of my power supply are as follows:

DC Output Load Max
+3.3V 28A
+5V 30A
+12V 34A
-5V 0.3A
-12V 0.8A
+5VSB 2A

+3.3V & +5V Combined Load: 200W
+3.3V, +5V, & +12V Combined Load: 480W
Total Max Power Output: 500W

Here's a list of all of the other components that will be drawing power in
my system, if it matters:

CPU: Intel LGA775 P4 530 3.0 GHz with stock heatsink/fan
Hard Drives: two SATA 250 GB 7200 RPM, one IDE 80 GB 7200RPM
Optical Drives: 16x dual layer DVD+/-RW, 52x32x52x CD-RW
Floppy Drive
a few cold cathode lights

I would think that I'll probably be okay with that power supply for now,
even though the +12V pin may come close to being maxed out (mostly depends
on how much power the video card actually draws, yes?). Bottom line: I just
want to know that I won't damage anything by running with the current power
supply for a while. Would you advise against it, or should I be okay until
I'm able to upgrade to a 24-pin ATX 12V 2.0 model?
September 20, 2004 12:25:59 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <XOl3d.6992$mb6.1587@newsread3.news.atl.earthlink.net>, "X
Offender" <nospamplease@earthlink.net> wrote:

> "Paul" <nospam@needed.com> wrote in message
> news:nospam-1909041015310001@192.168.1.177...
> > ...
> >
> > HTH,
> > Paul
>
> Wow. Thank you so much for taking the time to write such a clear and
> detailed explanation. That helps a great deal, as I know next to nothing
> about these power issues.
>
> The video card I'll be using is the PCI Express Gigabyte Radeon X600 XT
> (model # GV-RX60X128V). It does not utilize an auxiliary power connector. I
> have no idea what kind of power consumption to expect from this card. I'll
> also be running two 120 mm case fans. I won't be installing any other cards,
> as this motherboard has virtually everything built in (I'll be using onboard
> sound and networking).
>
> The specs of my power supply are as follows:
>
> DC Output Load Max
> +3.3V 28A
> +5V 30A
> +12V 34A
> -5V 0.3A
> -12V 0.8A
> +5VSB 2A
>
> +3.3V & +5V Combined Load: 200W
> +3.3V, +5V, & +12V Combined Load: 480W
> Total Max Power Output: 500W
>
> Here's a list of all of the other components that will be drawing power in
> my system, if it matters:
>
> CPU: Intel LGA775 P4 530 3.0 GHz with stock heatsink/fan
> Hard Drives: two SATA 250 GB 7200 RPM, one IDE 80 GB 7200RPM
> Optical Drives: 16x dual layer DVD+/-RW, 52x32x52x CD-RW
> Floppy Drive
> a few cold cathode lights
>
> I would think that I'll probably be okay with that power supply for now,
> even though the +12V pin may come close to being maxed out (mostly depends
> on how much power the video card actually draws, yes?). Bottom line: I just
> want to know that I won't damage anything by running with the current power
> supply for a while. Would you advise against it, or should I be okay until
> I'm able to upgrade to a 24-pin ATX 12V 2.0 model?

The two best articles on measuring video card power are here:

http://www.xbitlabs.com/articles/video/display/ati-vs-n...
http://www.xbitlabs.com/articles/video/display/ati-powe...

An X800XT draws 3.5A from +12V, and I would expect the X600XT to
be the same or less. I don't expect a problem in your case.

And your +12V current rating of 34A seems to be a lot more than
the 15-18A the system might be drawing under load.

HTH,
Paul
!