Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <413276d9$0$568$e4fe514c@news.xs4all.nl>, "Double Dutch"
<nospam@nospam.nl> wrote:
> Can u give me the url where ASUS tells about the PSU in relation to the
> P4P800-E Deluxe?
>
> Thansk in regards,
> DD
I've never seen that information offered by Asus. If you want to
develop your own estimates, I recommend visiting Intel
http://developer.intel.com/design/motherbd/products.htm
Select a board that is equivalent to the Asus board. Maybe a D865PERL
would have similar power consumption to the P4P800-E Deluxe.
http://developer.intel.com/design/motherbd/rl/index.htm
Then, select Technical Documents and download the manual
ftp://download.intel.com/design/motherbd/rl/C3176401.pdf
Table 43. DC Loading Characteristics
DC Current at:
Mode DC Power +3.3 V +5 V +12 V -12 V +5 VSB
Minimum loading 196 W 6 A 11 A 9 A 0.03 A 0.80 A
Maximum loading 330 W 12 A 15 A 16 A 0.10 A 1.60 A
The description of how Intel arrives at these numbers:
"[The table] lists the DC loading characteristics of the board.
This data is based on a DC analysis of all active components
within the board that impact its power delivery subsystems.
The analysis does not include PCI add-in cards. Minimum values
assume a light load placed on the board that is similar to an
environment with no applications running and no USB current draw.
Maximum values assume a load placed on the board that is similar
to a heavy gaming environment with a 500 mA current draw per USB
port. These calculations are not based on specific processor values
or memory configurations but are based on the minimum and maximum
current draw possible from the board¹s power delivery subsystems
to the processor, memory, and USB ports. Use the datasheets for
add-in cards, such as PCI, to determine the overall system power
requirements. The selection of a power supply at the system level
is dependent on the system¹s usage model and not necessarily tied
to a particular processor speed."
I suggest taking the +3.3V@12A and +5V@15A as estimates for those
voltage outputs. You can work out +12V consumption based on the
processor itself.
The +5VSB load is variable, and depends on whether you set the
USBPWR headers on the motherboard to run from +5V or +5VSB. I
recommend leaving the headers set for +5V, which is the factory
default. +5VSB is used for USB devices that you intend to wake
the computer from sleep or hibernate state. The Asus motherboard
manual will state in several places in the manual, how much
current is required for various +5VSB options. Now, on to
the +12V current consumption calculation...
Intel P4 3,0 GHz Processor (89W / 12V) * (1.0 / 0.90) = 12V @ 8.2A
80 Gb Maxtor S-ATA HDD 12V @ 0.5A idle (draws 2A during startup)
512 Mb memory (included in motherboard estimate)
ATI 9200 Graphics Card (negligible consumption)
CPU and chassis fans 12V @ 1A
(CD Drive - type unstated) 12V @ 0.5A
The 89W number is for a Prescott 3.0/FSB800 1MB cache processor. A
90 percent efficiency of the Vcore motherboard circuit is assumed.
The disk spends most of its time idling, at 0.5A. Video card
consumption becomes more significant for high end cards, and I list
your card as negligible, as it doesn't make that much difference to
your power supply.
Your 12V total, 8.2+0.5+1.0+0.5 = 10.2 amps
Now, look up your supply on the Aopen site:
http://asia.aopen.com.tw/products/power/default.htm
I will assume the supply is a 300GT, but you can download the correct
spec for yourself.
http://asia.aopen.com.tw/Products/images/POWER/products/ATX-300GT.pdf
ATX-300GT
MAXIMUM LOAD Our estimated load
+3.3V 7.5/20A \___ 175W max 12A \___ 3.3*12+5*15=115W OK
+5V 30/21.8A / 15A /
+12V 13A 10.2A
-12V 0.8A 0.1A
-5V 0.3A 0
+5VSB 2.0A Likely 1A or so.
Generally, I recommend 12V @ 15A for a minimal P4 system, and
if you have a high end video card, include the power numbers
listed in these articles:
http://www.xbitlabs.com/articles/video/display/ati-powercons.html
http://www.xbitlabs.com/articles/video/display/ati-vs-nv-power.html
When you shop for a power supply, total power rating in watts does
not tell the whole story. For example, there were some 500W power
supplies for sale within the last year, that had only a 12V @ 10A
rating, insufficient even for your system. Most reputable power
supply manufacturers list the individual output ratings of their
supplies, both on the label of the supply, and on their web
site, making it easier to shop for the correct size. The supply
provided with your computer case above, appears to be adequate
for the job, but if you plan on adding any components which
consume a lot of power, you may want to revise the estimates
above.
There are a couple of web sites that offer a spreadsheet approach
to calculating power consumption. Some of these sites over
estimate the power consumption, leading to overly pessimistic
results and a large expensive power supply is the answer. It
takes a lot of work to refine these estimates, and find the
errors in calculation, so do not assume because a web site
offers such a service, that the answer will be a correct one.
As for your original problem:
"Only if I switch off the pc completely, the problem comes up."
When this happens, check that the green LED on the motherboard
is lit, indicating that the power supply is feeding +5VSB. If
you flip the switch on the power supply to "ON" on the back of
the computer, the green LED should come on. If it does not,
the +5VSB could be overloaded, or there could be a fault with
the power supply. If no +5VSB is available, it will be impossible
to start the computer.
HTH,
Paul
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