The motherboard has two fan connectors (at least according to the
motherboard picture and available headers). Item 18 connects to the
CPU fan,
and the CPU fan also doubles as the case fan. So that fan
does two jobs - it cools the CPU, but it also moves air through the
Dell computer case.
http://support.dell.com/support/edocs/systems/xps410/en/SM_EN/techov.htm
Item 16 is labeled "rear fan connector". Open the computer case,
and trace where the wire assembly connected to item 16 leads. if the
wire goes to the power supply (which is the most likely solution),
then the rear fan *is* the PSU fan.
As the load goes up on the power supply, the power supply fan speed
should increase. This may be implemented, by the power supply
sensing the temperature of a key component inside the power supply,
and using the temperature of that item, to set the PSU fan speed.
If the "rear fan" connector is sensing an RPM signal from the PSU,
then it has the ability to check the fan speed. If the fan is running
faster than normal, most BIOS would not care about that. Normally,
it is a low fan speed, which is a trigger event. I don't know if
Dell is doing something different in this case or not. If a
fan runs slow enough, the hardware monitor chip will read out
"zero RPM", as there is a limit as to the minimum RPM value
that can be measured by a hardware monitor. On my old P4 system,
the minimum RPM was 1800 RPM. On modern systems, you might be able
to read 500 RPM without a problem. The range of the fan measurement
circuit, is determined by a clock source and dividers inside the
hardware monitor. The difference between 1800 and 500 RPM as the
minimum value, could have been done entirely by programming the
hardware monitor chip differently.
There are two reasons to make a CPU fan run faster. Either the CPU
temperature is higher. Or the computer case ambient air temperature
is higher. When the air around the CPU fan is hotter, it makes it
harder for the cooler to do its job. To compensate for that,
a higher fan speed can fix it. Some Intel retail coolers use that
compensating method. Intel retail coolers use a thermistor in the
fan hub, to measure the air temperature. The fan runs faster, as
the air gets hotter.
If the BIOS is monitoring the CPU temperature, it may decide to increase
the PWM (pulse width modulation) setting, on the PWM wire. It is possible
the Dell main fan has PWM control as well. So you could use a program
like Speedfan, and adjust the fan speed. The PWM wire, carries a signal
from the motherboard to the fan, telling the fan how fast to run. So
that is a second potential control method.
The first method cannot be changed by Speedfan (almico.com). The
PWM method, on the other hand, may be programmable, in which case
Speedfan may be used to make adjustments.
Since the Dell main fan, provides cooling for the computer case,
as well as for the CPU, it may be considering both temperatures.
If the CPU is cool and the case air is hot, then the fan should
still spin fast. If the CPU is hot, and the case air is cool,
the fan should still spin fast.
So those are some possibilities you could investigate.
I notice on the manual page that covers removing components, there
is mention of a "card fan" as well, but I don't see any place on
the motherboard to plug that in. It could mean that the card fan
is not monitored, as to its speed.
This is a picture of your power supply label (the existing one).
http://i.ebayimg.com/04/!BVTFgHgCGk~$(KGrHgoOKkYEjlLm(TDiBKR3NfE2Zg~~_1.JPG
Your current power supply rating, extracted from that label:
3.3V @ 17A, 5V @ 22A, 12V1 @ 18A, 12V2 @ 18A, -12V @ 1A, +5VSB @ 2A
<----- 150W max ---> <----- 360W max ----->
<------- (not shown in picture, but could be 375W ---------------->
The 360W limit on both 12V rails combined, means there is at most
30A to work with, not the more 36A you'd get by adding the numbers
together.
Your Q6600, if it is a G0, draws 95W. The Vcore switching
conversion circuit, near the CPU socket, is 90% efficient, which
is where the 0.90 in the following equation comes from.
http://processorfinder.intel.com/details.aspx?sSpec=SLACR
(95W / 12V) * (1 / 0.90) = 8.8A from 12V2
You can draw up to 18A from 12V1. That would power the video card,
disk drives and fans.
The Nvidia reference 8800GTS 512MB card is 99W at 3D max power.
http://www.xbitlabs.com/articles/video/display/xfx-gf8800gts_4.html#sect0
Details here (top item).
http://www.xbitlabs.com/images/video/xfx-gf8800gts-xxx/xfx8800gts_power_full.png
99W / 12V = 8.25A from 12V1
A hard drive draws about 0.6A from 12V. Say you had two of those.
A CDROM draws 1.5A from 12V, when media is present in the tray. In
a gaming situation, a CD may need to be present. I've actually
measured my CD drive, and it only uses 1.0A at high speed. 1.5A
is the value printed on the label of the drive.
Dell fans probably exceed my usual estimate of 0.5A. The main Dell
fan is usually a monster, capable of drawing over an ampere. I'll
give it 0.5A, assuming it is not running at full speed.
Total for 12V1 = 8.25A + 0.6 + 0.6 + 1.5 + 0.5 = 11.45A
That is 11.45A out of 18A available on 12V1.
So basic current draw appears OK. The total 12V current is 12V1 + 12V1 =
8.8A + 11.45A = 20.25A
Now, for a total power calculation.
(12V total) + HDD + HDD + CDROM + Motherboard/RAM + 5VSB
standby/USB
20.25A * 12V + 5V*1A + 5V*1A + 5V*1.5A + 50W + 10W = 320.5W
The actual consumption is likely to be less than this, even at peak.
This is less than the 375W total limit.
I expect the higher consumption, is making all the fans run faster.
Seems normal, considering what you've done. The main Dell fan is
a monster, capable of making a deafening noise if provoked
I hope the video card is using a second slot cover, to dump
heat output.
If you wanted to replace the power supply, these are the issues I see
1) Does the item 16 header connect to the PSU fan ? If so,
it might be good for the replacement power supply to do the
same. If that is not possible, you'll need to connect *some*
three wire fan, to the Item 16 fan header, so the BIOS is fooled
into seeing an RPM signal. That is only important, to avoid the
computer switching off, or delivering the "F1 warning" at startup.
If the BIOS doesn't care about the signal coming from item #16 header,
then you don't care either.
2) Is the computer using the "DC Power Connect P4" ?
It is a 2x3 connector.
Pin Number Signal Name 18-AWG Wire
1 N/C N/C
2 COM Black
3 COM Black
4 +3.3 VDC Orange
5 +5 VDC Red
6 +12A VDC Yellow
I've seen this connector in Dell documentation before, but nobody
has been able to tell me, what it is plugged into. A standard
ATX power supply, does not have that connector. The connector
is a 2x3, and looks to be an "Auxiliary" power connector for
some purpose.
3) The power supply has P12, as a standard PCI Express 2x3. Since the
8800GTS only has one PCI Express 2x3 connector, the replacement
supply should have at least one of those.
So the biggest challenge, in replacing the supply, is deciding
whether P4 is necessary, and determining what it powers. Making
a substitute connector, would require considerable screwing
around with 18ga wire and Molex connectors, and voiding the
warranty on the new power supply.
HTH,
Paul
