In article , "Arifi Koseoglu"
wrote:
"Paul" wrote in message
...
In article .com,
"arifi" wrote:
Hello everyone,
At work we wish to build a small-footprint demo computer using one of
those thin (10cm / 4 inches high) desktop cases, which will be easy to
carry to customer's sites, and such. We prefer this way rather than
buying a strong laptop since we believe such a system will perform
better and be more flexible.
The case we have found has a power suply capable of producing 230
Watts, and they claim it easily drives P4 systems. The case can house
microATX size MoBos. The power supply is a thin and long one custom for
this case, so there is no easy way to upgrade the PSU.
Being primarily an ASUS house, we searched for "microatx" and "matx" on
their web site, and the following motherboards were listed:
P5GD1-VM
P4GE-MX
P4R800-VM
P4P800-VM
P4BP-MX
P4S800-MX
P4SP-MX
P4SP-MX SE
P4V533-MX
P4VP-MX
A7N8X-VM
A7N8X-VM/400
P5S800-VM
K8S-MX
I would assume all to be nice boards, but we have not been able to find
conclusive information about how much Wattage the complete system built
around one ot them would require.
The system will contain the Motherboard, 2x512MB DDR RAM, 1x P4 CPU, 1x
SATA drive, CDROM Player, cabled keyboard and cabled mouse. No other
attachments except for a monitor or a projection device. The amount of
computing power we need is at the order of a P4-2800 with 1Meg Cache,
but we do know that we will have to settle with the max. that the power
supply can drive.
There are Power Supply calculators out there, but the ones I have
looked into do not consider all-in-one boards like the ones above where
the graphics card, lan etc are all on the motherboard.
So the Question is: How can I find out how much power these
motherboards will draw? What is the strongest CPU/MoBo combination I
can use with the 230W PS we have? (he system will be run at rated
speeds - no overclocking)
I will appreciate any information and any pointers deeply.
Many thanks in advance,
-arifi
For power estimation purposes, you could go to the Intel motherboard
web page, and look at some boards there. Each board has a manual,
and there is a power estimate section.
http://developer.intel.com/design/motherbd/products.htm
This is the manual for the D915GAG (microATX builtin graphics)
These numbers are maximums, in every sense of the word.
I use these numbers only to get some idea of what the
non-CPU rails will be drawing.
ftp://download.intel.com/design/moth...g/C6860002.pdf
Mode DC Power +3.3V +5V +12V -12V +5VSB
Minimum loading 200.00W 3.30A 10.00A 900mA 0.03A 0.80A
Maximum loading 300.00W 6.00A 14.00A 16.00A 0.10A 1.40A
Based on their description, start with the minimum loading
spec. Your two DIMMs will add about 5W each. The +12V
draw, exclusive of the processor, would be for fans.
A Prescott P4 2.8/FSB800/1MB LGA775 has a TDP of 84 watts
(see page 74 table 5-1).
ftp://download.intel.com/design/Pent...s/30235101.pdf
The 84W comes from +12V. The Vcore converter could be
considered to be 90% efficient (based on the fact that the
MOSFETs and toroids don't get warm to the touch). The
+12V current required is thus (84/12)*(1/0.90)=7.8A .
(A 2.8GHz/FSB800/512KB Northwood is 69.7W == 6.45A)
Adding this together, and assuming the DIMM power comes
from +3.3V (3 amps to give the requires 10 watts), gives
a Prescott based 2.8Ghz system with power of:
Mode DC Power +3.3V +5V +12V -12V +5VSB
Minimum loading --- 3.30A 10.00A 0.9A 0.03A 0.80A
DIMMs --- 3.0A --- --- --- ---
Processor --- --- --- 7.8A --- ---
Disk drive --- --- 1.0A 0.5A --- ---
CD/RW Drive --- --- 1.0A 1.5A --- ---
Total 212.6W 6.30A 12.0A 10.7A 0.03A 0.80A
(Fan current included in the 0.9A minimum)
This online calculator will also work out powers for you.
http://takaman.jp/D/?english
Other details. The hard drive will draw 2 amps from +12V
while spinning up. (Since the processor doesn't run at
full power in the BIOS, this is not an issue. On a
system I measured with my ammeter, CPU power might be
about 50% of max, while sitting in the BIOS as the drive
spins up.)
The CD/RW will only draw the 1.5 amp number while spinning
as well. Optical drive currents drop substantially when they
are not in use (no CD in drive). The listed hard drive
current might be representative of a seek operation.
You can find replacement supplies. But it won't be
easy.
http://www.pcpowerandcooling.com/prices/
There are a couple of 1U power supplies here. Due to the
small fan size, these will likely make a lot of noise
if you draw decent power from them.
http://www.pcpowerandcooling.com/pro...ndex_hp_1u.htm
As Rob pointed out, there is a whole spectrum of power
saving solutions out there. But you'll need time to experiment
with them, to find the right one.
As for actual measured systems - these measurements are
exclusive of video card power. (My 9800pro video card
can draw , but when the video card is
working that hard, the processor generally cannot run
at full power, due to waiting for the video card to
complete operations. A FX5200 low performance type video
card, would eliminate that extra power.) There is one hard
drive and one CD on these systems.
These two systems are roughly equal in gaming computing power.
A fast video card can add 38W to the power numbers. This shows
you how close a real system would get to your 230W total rating.
With a FX5200 class video card, you would be in good shape.
(Processor current comes from +5V...)
A7N8X-E 3200+ 2x512MB dual channel
(running Prime95 = 106W)
(Processor current comes from +12V...)
P4C800-E 2.8G/FSB800/512K 2x512MB dual channel
(running memtest86 = 113W)
The only thing that seems to be amiss, is Intel's user
manual estimates a large +5V consumption, and at least
with my P4C800-E, the power seems to come more from
+3.3V . This means, depending on which company makes the
motherboard, the same amount of power will be used, but
it could either be drawn heavily from +3.3V or +5V rail.
In the examples above, the AthlonXP board uses the +5V supply
to power the processor. Pentium4 and Athlon64 boards use
+12V to power the processor (that is why they both use the
2x2 power connector, for extra +12V current). Depending on
how the amps pan out on the various outputs of your power
supply, may help you decide whether a +5V powered processor
or a +12V powered processor, is the right answer.
As for Athlon64, the TDPs are listed here. Some of the
Athlon64's have very nice power numbers. Whether they will
work for you, really depends on whether your application mix
works well with Athlon64's strengths and weaknesses. If you
were building a gaming box, the Athlon64 would be the easy
choice.
http://www.amd.com/us-en/assets/cont...docs/30430.pdf
HTH,
Paul
Dear Paul,
Hello again, and of course MANY MANY THANKS for the (once again) very much
detailed information.
After reading your post, the case I mentioned actually arrived and I had the
chance to look at the actual label on the power supply: First of all, the
PSU has a label stating that it is a 350W PSU and not a 230W as we were told
by the supplier. HOWEVER, the ratings on the label are as follows:
-----------------------------------------------
+3.3V | +5V | +12V | -5V | -12V | +5VSB
7A | 13A | 6A | 0.5A | 0.8A | 1A
-----------------------------------------------
75W Max |-------| 9.6 W Max |-------
-----------------------------------------------
3 5 0 W
-----------------------------------------------
Now, here is how I interpret the label:
1. The 75W Max. under the +3.3V & +5V columns probably means that the
combined simultaneous load on these lines cannot exceed 75Watts, while the
+3.3V line can carry 3.3x7=23.1W and the +5V line 5x13=65W.
2. The +12V line is capable of producing 12x6=72W.
3. The 9.6W Max. under the -5V & -12V columns probably means that the
combined simultaneous load on these lines cannot exceed 9.6Watts, while
the -5V line can carry 5x0.5=2.5W and the -12V line 12x0.8=9.6W. Prescott
based 2.8Ghz
4. The +5VSB line is capable of producing 5x1=5W. (By the way, what does VSB
mean?)
5. Taking into account the 75W and 9.6W Maximums, and adding the +12V and
+5VSB powers, I calculate the actual total power to be 75 + 9.6 + (72) + (5)
= 161.6W YUCK !!! Is this calculation correct?? Where is the claimed 350W ??
You mention that the P4 and Athlon64 get their CPU power from the +12V line,
while the AthlonXP from the +5V line. The P42.8Prescott has a TDP of 84Watts
(your post) and the Athlon64 3000+ a Max. TDP of 89Watts (Athlon64 Power and
Thermal Data Sheet.)
Does that now mean that I cannot run either of these CPUs using this PSU or
am I missing something?
Under what conditions are the maximum Power levels reached? Typical loading
of CPU on the Demo system will be a sequence like [Short/Intermediate
Peak] - [Longer Idle] - [Short Peak] - [Longer Idle] - [Short/Intermediate
Peak] - [Longer Idle] ...
Here comes where I get confused again. In your post you mention:
(Processor current comes from +5V...)
A7N8X-E 3200+ 2x512MB dual channel
(running Prime95 = 106W)
(Processor current comes from +12V...)
P4C800-E 2.8G/FSB800/512K 2x512MB dual channel
(running memtest86 = 113W)
Here you calculate the total Wattage by collecting values from all rails
(3.3, 5, 12). Then probably I should not expect all the CPU power from the
12V rail alone in the Athlon64 and Prescott cases... If so, I could still
use and Athlon64 or Prescott... But in your table you had put the 7.8A for
the CPU completely on the 12V line of the Prescott based 2.8Ghz system...Or
??
Confused... I hope I am not asking the obvious.
Many Thanks,
Cheers,
-arifi
That has got to be the worst power supply I've ever seen.
Are you sure that isn't the *minimum* load ? Some supplies
have two sets of number, some minimum numbers and some
maximum numbers. The power supply will not regulate to
within 5% of nominal output voltage, unless the minimum
load is applied.
Is it possible for you to give more info about the
case and power supply you bought ? Do you have a
URL for a website, with details about the product,
and maybe a picture of the label on the power supply ?
I think you understand the basic principles. The power
supply has limits for the maximum current that can
come from any individual output, and there are also
limits for certain groups of outputs. The group limits
are caused by using a multi-winding transformer in the
output. If two windings are supplying current, the thermal
load on the transformer will bear some relationship to that
load. Thus, the label on the power supply will state a
combined total power for those outputs. The total power for
the power supply should also be based on some fundamental
limit of the supply (maybe the rating of the primary side
and switching components ?). In any case, all those limits
apply simultaneously, so you cannot exceed any output's
maximum current, neither can you exceed one of the group
power ratings.
If the ratings on that label are for real, you've got enough
power *maybe* for a Pentium-M or a Via EPIA. There isn't
enough current available on +5V or +12V to run any of the
motherboards I've got here (my home collection).
So, work on verifying that label.
The +5VSB stands for +5 volts standby. The +5VSB supply
continues to run when the computer is in S3 Standby. The
suspend to RAM function requires power to keep the memory
chips refreshed, and that comes from +5VSB. The +5VSB is
also used for any Wake on LAN, Wake on Ring, or similar
functions, that require portions of the other chips to be
operational while the computer is in standby. These days,
2 amps is a good number for +5VSB. If you only have
one amp to work with, then all wake functions and any
USB/keyboard header settings must be set not to use +5VSB.
My measurements for my A7N8X-E and P4C800-E were done with
a clamp-on DC ammeter. This is a device based on a Hall
probe, that converts the magnetic field around a conductor
into a voltage. My meter will measure AC or DC current in
a conductor, by simply clamping the meter around a
conductor or a group of conductors (the magnetic fields add).
This is how I measured my home systems. You grab all the +5V
wires on the ATX 20 pin power cable and put them in the jaws
of one of these, then measure the current flowing in the
bundle of wires. Useful for determining how close to the
limits you are. Mine cost $400 Canadian.
http://www.extechproducts.com/produc...41_942_947.pdf
Paul