Water cooling - how many case fans would still be necessary? Tower case recommendations?

Discussion in 'Asus' started by Andrew Hamilton, Jun 5, 2009.

  1. I typically build full-tower systems but I'm tired of the fan noise.

    For my next build, I'm probably going to do an Intel i7 920 and one of
    the ASUS P6T models. Overclocked of course, because it sounds very
    easy to get good results.

    I'm not sure about the graphics card or cards, because I'm not a
    gamer, but I do run Photoshop. Also, I have four drives in my system
    now and I'll probably carry those over to my new system. Also, to
    make Photoshop really, really run well, I'm thinking about a 12 GB
    system, e.g. six 2GB memory sticks.

    So I know I need "strong" cooling. That could be a lot of fans, or I
    could go to water cooling.

    Without getting into a detailed discussion of exactly which
    water-cooling system and extreme overclocking, I'm wondering about
    some basic questions:

    How many fans can I eliminate or "downspec" (slower, quieter) with
    water-cooling the CPU? Memory? VGA? Chipset? Anything else?

    Is it even possible to eliminate the intake and exhaust case fans? Or
    at least run them very slowly?

    If I use an external radiator, am I stuck with noisy radiator fans, or
    can I pick a system that gives me a very "quiet" radiator system?

    Any suggestions for full-tower cases that are well-designed for
    water-cooling? (or not?) I would be happy with a plain-looking case,
    without side window, illuminated interior or fans, anything like that.
    Thanks in advance.

    Andrew Hamilton, Jun 5, 2009
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  2. You might want to look at www.silentpcreview.com as they talk about all
    the things you are asking about.
    Michael W. Ryder, Jun 5, 2009
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  3. Thanks Funny thing. My current system is housed in an Antec P180,
    which gets pretty favorable comments on this site. But I would like
    my next system (or actually, case) to be a lot quieter. In this
    system, I have all three case fans on high and I have four hard
    drives, a combination of Seagate 7200.11 (not 12!) and Hitachi

    Andrew Hamilton, Jun 6, 2009

  4. How about the memory sticks? Corsair sells fans for their Domininator
    series. Is this a gimmick? I noticed that they even have a
    water-cooling block on their website for this memory series.
    Thank you. This is good to know.
    I will probably get a case with a bottom-mounted power supply. This
    seems to be more and more popular with bigger tower cases these days.
    Since the PS fan blows out, then I guess I would need one intake fan
    with more airflow than the PS fan.
    That sounds nice, but is just not practical for me.
    Thanks. I appreciate your comments.

    Andrew Hamilton, Jun 6, 2009
  5. My current case at home is an original Sonata with an after-market sound
    deadening foam kit installed. It is almost silent until my video card's
    fan kicks in. Maybe you should look to see if there are any kits
    available for your case.
    You might also look at
    http://www.tomshardware.com/forum/235723-29-antec-p180-watercooling for
    some ideas.
    Michael W. Ryder, Jun 6, 2009
  6. From a thread from three months ago:

    In reading a LOT about air vs. water cooling, some people say that you
    should consider water-cooling "even the MOSFETs." I know what the
    acronym stands for, but not what this part actually does on a P6T
    series motherboard.

    Where is(are) the MOSFET(s) on this board?
    Select the left thumbnail image from the right side of this page.

    Thank you.

    Andrew Hamilton, Sep 24, 2009
  7. Andrew Hamilton

    Mike Paff Guest

    The MOSFETs being referred to are part of the voltage regulator
    They are under the two copper-colored heat sinks above and to the
    right of the CPU socket. It looks like that board uses a heat-
    pipe arrangement to cool the MOSFETS and north/south bridge chips
    using the airflow generated by the CPU cooler.

    If you are planning to use a fanless CPU cooler of some sort
    (water cooling or a large passive heatsink), you'll either need to
    provide an alternate source of airflow over those copper heatsinks
    or remove the heat-pipe system and water cool all four of the areas
    covered by it.
    Mike Paff, Sep 24, 2009
  8. Andrew Hamilton

    Paul Guest

    MOSFET water blocks. Acrylic top, copper bottom, O-ring seal.
    "EK-Mosfet ASUS X58 KIT"



    Example of original heatpipe assembly.



    As for what MOSFETs do, see page 11 here for a sample schematic of a VCore.
    VCore circuitry surrounds a CPU socket, and provides power at up to levels
    of around 100 amps at a low voltage to the CPU core logic. This power design
    might have been used on a P4 motherboard.


    A conventional switching regulator consists of the "brains", a chip with more
    pins at the bottom of page 11. They try not to make it dissipate too much power,
    so the PWM1,PWM2,PWM3,PWM4 signals are buffered with 8 pin chips, before the drive
    signals arrive at the MOSFETs. In that example design, there are three
    MOSFET transistors per phase (Q1,Q2,Q3 belonging to one phase). The toroid coil
    or square cube is L2. Q1 handles the "high side". Q2 and Q3 are "low side"
    MOSFETs. Either Q1 is turned on, or Q2+Q3 are turned on. Since Q1,Q2,Q3 have
    large gate capacitance (like 3000 pF), the tiny eight pin chip ends up pumping
    current at the 1 amp level, in pulses, to charge the gate on each transistor.
    It makes the whole process easier to cool, if the chips are split up, and the
    8 pin driver is separate. The 8 pin driver should get a little warm on its own.

    Q1,Q2,Q3 are the MOSFETs. They're supposed to operate saturated. In other
    words, when commanded to conduct, the channel resistance drips to Rds_on,
    and a lot of current flows. If Rds_on is low enough, the I squared R loss is
    pretty low, so the MOSFET shouldn't get hot. You can make MOSFETs
    "bigger", but then the gate capacitance goes up, and the eight pin
    driver would start to fry from the load. So the choice of the number
    of MOSFETs, their RDS_on, is a trade off between "hot MOSFETs" and
    "hot driver chip". The price of the MOSFETs, also plays a part in their

    L1 and C1 thru C6, are the input side filtering. They help prevent the
    pulsed operation of the Vcore circuit, from being felt by the power
    supply. On the output side, C21 thru C28 is the bank of capacitors
    for the output. Capacitors filter the AC component coming from
    L2, L3, L4, and ampere level currents will be flowing through C21 thru C28.
    The caps have to be rated for some level of "ripple current", to operate
    for thousands of hours trouble free. Multiple capacitors are required, to get
    enough total ripple current rating. Otherwise, one fat ass capacitor
    could have been used, if all they wanted was the capacitance itself.
    The capacitance is not quite as critical, as the ripple current rating.

    I still haven't found any oscilloscope signal pictures, to demonstrate
    what it is doing, so I'll leave the rest of the explanation to the
    fine datasheet from Analog Devices.

    On page 19, you can see a drawing of the layout of the circuit. The
    three MOSFETs on each phase, haven't been place optimally for usage
    with a rectangular cooler to fit over the top of them. So the
    assumption in that picture, is likely air cooling coming from the
    "spill air" from the CPU cooling. You'd need to line the MOSFETs up
    in a neat row, to place a cooler over them.

    You'll notice, in the figure on page 19, the mention of a thermistor.
    On my P4C800-E, Asus didn't include that. If they'd included the
    thermistor, the Vcore would have been able to better handle
    transitions from "busy" to "idle". The Vcore voltage is off by 0.05
    volts for a few seconds, while the copper coils cool off. If
    the thermistor had been included, the circuit would have been
    temperature compensated, and the voltage error would have been
    minimal. So even when you pay for a "Deluxe" motherboard, the design
    isn't always as "Deluxe" as it could be. That is what I like, about
    digging up these datasheets.

    Paul, Sep 24, 2009
  9. Andrew Hamilton

    Arno Guest

    Watercoling the mosfets is generally not needed. Thay have a far
    better temperature tolerance than the other semiconductors. Hwever
    you may want too cool the filter capacitors that are in close
    proximity. This can basically be done with air. The second problem
    is that most mosfet "coolers" sit on the top of the mosfets, which
    is thermally insulated by epoxy resin. The heat oes out the copper
    ins on the bottom.

    As a consequence the only good waty to watercool mosfets would be
    to dismount them from the board and mount them on a copper plate
    or the like with their own copper mounting area. This is not
    really possible.

    To sum up: mosfet coolers are ineffective. However good airflow
    on the area lengthens the lifetime of the capacitors there.

    Arno, Sep 28, 2009
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