92mm vs. 90mm Case Fan

Discussion in 'Dell' started by Daddy, Apr 30, 2011.

  1. Daddy

    Daddy Guest

    I'm looking to upgrade the case fan in my Studio XPS 8100.

    The existing case fan is a Foxconn PVA092G12M. There's scant information
    available from a Google search; this is either a 90mm fan or a 92mm fan.
    My question is: Does it matter whether I use 90mm or 92mm? It's 2 lousy
    millimeters.

    I'm only asking because there are hardly any 90mm fans on Newegg - and
    none with 3 pins, but there are tons of 92mm models.

    Daddy
    Daddy, Apr 30, 2011
    #1
    1. Advertising

  2. Daddy

    Pen Guest

    On 4/30/2011 11:30 AM, Daddy wrote:
    > I'm looking to upgrade the case fan in my Studio XPS 8100.
    >
    > The existing case fan is a Foxconn PVA092G12M. There's scant
    > information available from a Google search; this is either a
    > 90mm fan or a 92mm fan. My question is: Does it matter
    > whether I use 90mm or 92mm? It's 2 lousy millimeters.
    >
    > I'm only asking because there are hardly any 90mm fans on
    > Newegg - and none with 3 pins, but there are tons of 92mm
    > models.
    >
    > Daddy

    I found it right off. 92mm
    http://www.notebookparts.com/products/description.php?II=57471
    Pen, Apr 30, 2011
    #2
    1. Advertising

  3. Daddy

    Pen Guest

    On 4/30/2011 5:11 PM, Daddy wrote:
    > Pen wrote:
    >> On 4/30/2011 11:30 AM, Daddy wrote:
    >>> I'm looking to upgrade the case fan in my Studio XPS 8100.
    >>>
    >>> The existing case fan is a Foxconn PVA092G12M. There's scant
    >>> information available from a Google search; this is either a
    >>> 90mm fan or a 92mm fan. My question is: Does it matter
    >>> whether I use 90mm or 92mm? It's 2 lousy millimeters.
    >>>
    >>> I'm only asking because there are hardly any 90mm fans on
    >>> Newegg - and none with 3 pins, but there are tons of 92mm
    >>> models.
    >>>
    >>> Daddy

    >> I found it right off. 92mm
    >> http://www.notebookparts.com/products/description.php?II=57471
    >>

    >
    > Yes, I saw that one as well. But sellers on eBay describe it
    > as 90mm.
    >
    > My question is, does it really matter whether I buy a 90mm
    > or a 92mm fan? I mean, if I'm wrong on the size, I'm only
    > wrong by 2 millimeters.
    >
    > Daddy

    Go ahead and use it and drill out the holes if it's wrong.
    Pen, Apr 30, 2011
    #3
  4. Daddy

    mm Guest

    On Sat, 30 Apr 2011 11:30:24 -0400, Daddy <> wrote:

    >I'm looking to upgrade the case fan in my Studio XPS 8100.
    >
    >The existing case fan is a Foxconn PVA092G12M. There's scant information
    >available from a Google search; this is either a 90mm fan or a 92mm fan.
    >My question is: Does it matter whether I use 90mm or 92mm? It's 2 lousy
    >millimeters.
    >
    >I'm only asking because there are hardly any 90mm fans on Newegg - and
    >none with 3 pins, but there are tons of 92mm models.
    >
    >Daddy


    Penn's right. It might even fit, probably will -- the screw only has
    to cut one little groove at one place in the hole perimeter -- and if
    you have to make holes larger, maybe you should make a couple holes in
    the metal case larger so the same screws fit all four plstic holes.

    An excuse to buy a new tool, a reamer that has a T-handle and will
    make the metal hole larger, a tiny bit at a time.
    mm, May 1, 2011
    #4
  5. Daddy

    Daddy Guest

    mm wrote:
    > On Sat, 30 Apr 2011 11:30:24 -0400, Daddy <> wrote:
    >
    >> I'm looking to upgrade the case fan in my Studio XPS 8100.
    >>
    >> The existing case fan is a Foxconn PVA092G12M. There's scant information
    >> available from a Google search; this is either a 90mm fan or a 92mm fan.
    >> My question is: Does it matter whether I use 90mm or 92mm? It's 2 lousy
    >> millimeters.
    >>
    >> I'm only asking because there are hardly any 90mm fans on Newegg - and
    >> none with 3 pins, but there are tons of 92mm models.
    >>
    >> Daddy

    >
    > Penn's right. It might even fit, probably will -- the screw only has
    > to cut one little groove at one place in the hole perimeter -- and if
    > you have to make holes larger, maybe you should make a couple holes in
    > the metal case larger so the same screws fit all four plstic holes.
    >
    > An excuse to buy a new tool, a reamer that has a T-handle and will
    > make the metal hole larger, a tiny bit at a time.



    "... a reamer that has a T-handle and will make the hole larger, a tiny
    bit at a time ..."

    Didn't they use something like that in the Inquisition?

    Seriously, thanks for everyone's help.

    Daddy
    Daddy, May 1, 2011
    #5
  6. Daddy

    Ben Myers Guest

    On Apr 30, 11:30 am, Daddy <> wrote:
    > I'm looking to upgrade the case fan in my Studio XPS 8100.
    >
    > The existing case fan is a Foxconn PVA092G12M. There's scant information
    > available from a Google search; this is either a 90mm fan or a 92mm fan.
    > My question is: Does it matter whether I use 90mm or 92mm? It's 2 lousy
    > millimeters.
    >
    > I'm only asking because there are hardly any 90mm fans on Newegg - and
    > none with 3 pins, but there are tons of 92mm models.
    >
    > Daddy


    I don't understand "upgrade". A fan that blows more cubic feet per
    minute? Or simply a replacement fan for one that does not work as
    well any more? If the latter, just get another new one per its Dell
    part number... Ben Myers
    Ben Myers, May 1, 2011
    #6
  7. Daddy

    Daddy Guest

    Ben Myers wrote:
    > On Apr 30, 11:30 am, Daddy <> wrote:
    >> I'm looking to upgrade the case fan in my Studio XPS 8100.
    >>
    >> The existing case fan is a Foxconn PVA092G12M. There's scant information
    >> available from a Google search; this is either a 90mm fan or a 92mm fan.
    >> My question is: Does it matter whether I use 90mm or 92mm? It's 2 lousy
    >> millimeters.
    >>
    >> I'm only asking because there are hardly any 90mm fans on Newegg - and
    >> none with 3 pins, but there are tons of 92mm models.
    >>
    >> Daddy

    >
    > I don't understand "upgrade". A fan that blows more cubic feet per
    > minute? Or simply a replacement fan for one that does not work as
    > well any more? If the latter, just get another new one per its Dell
    > part number... Ben Myers


    Lol ... I knew somebody would eventually ask me "why are you even doing
    this?" And the answer is: I, uh, don't really have a good reason. I
    guess I'm trying for a little more quiet. I replaced Dell's stock video
    card, and that made my computer noticeably quieter. And case fans are
    cheap and easy to install, so I figured give it a shot. The Foxconn
    blows 45 CFM. If I can find something real quiet that blows as much air,
    I'll try it.

    My next project is an upgraded power supply. In a larger sense, all this
    is preparation for building my first ever computer.

    Daddy
    Daddy, May 1, 2011
    #7
  8. Daddy

    Ben Myers Guest

    On Apr 30, 11:16 pm, Daddy <> wrote:
    > Ben Myers wrote:
    > > On Apr 30, 11:30 am, Daddy <> wrote:
    > >> I'm looking to upgrade the case fan in my Studio XPS 8100.

    >
    > >> The existing case fan is a Foxconn PVA092G12M. There's scant information
    > >> available from a Google search; this is either a 90mm fan or a 92mm fan.
    > >> My question is: Does it matter whether I use 90mm or 92mm? It's 2 lousy
    > >> millimeters.

    >
    > >> I'm only asking because there are hardly any 90mm fans on Newegg - and
    > >> none with 3 pins, but there are tons of 92mm models.

    >
    > >> Daddy

    >
    > > I don't understand "upgrade".  A fan that blows more cubic feet per
    > > minute?  Or simply a replacement fan for one that does not work as
    > > well any more?  If the latter, just get another new one per its Dell
    > > part number... Ben Myers

    >
    > Lol ... I knew somebody would eventually ask me "why are you even doing
    > this?" And the answer is: I, uh, don't really have a good reason. I
    > guess I'm trying for a little more quiet. I replaced Dell's stock video
    > card, and that made my computer noticeably quieter. And case fans are
    > cheap and easy to install, so I figured give it a shot. The Foxconn
    > blows 45 CFM. If I can find something real quiet that blows as much air,
    > I'll try it.
    >
    > My next project is an upgraded power supply. In a larger sense, all this
    > is preparation for building my first ever computer.
    >
    > Daddy


    I forgot that the Studio XPS 8100 is a tower computer, not a laptop!
    Your reasoning makes sense for a tower or desktop. It would be at
    least mildly deranged to try to replace a fan with anything other than
    a stock item for a LAPTOP.

    But pay attention to the connectors and wires for fan replacement in a
    Dell... Ben Myers
    Ben Myers, May 1, 2011
    #8
  9. Daddy

    Justin Guest

    On 4/30/11 5:11 PM, Daddy wrote:
    > Pen wrote:
    >> On 4/30/2011 11:30 AM, Daddy wrote:
    >>> I'm looking to upgrade the case fan in my Studio XPS 8100.
    >>>
    >>> The existing case fan is a Foxconn PVA092G12M. There's scant
    >>> information available from a Google search; this is either a
    >>> 90mm fan or a 92mm fan. My question is: Does it matter
    >>> whether I use 90mm or 92mm? It's 2 lousy millimeters.
    >>>
    >>> I'm only asking because there are hardly any 90mm fans on
    >>> Newegg - and none with 3 pins, but there are tons of 92mm
    >>> models.
    >>>
    >>> Daddy

    >> I found it right off. 92mm
    >> http://www.notebookparts.com/products/description.php?II=57471

    >
    > Yes, I saw that one as well. But sellers on eBay describe it as 90mm.
    >
    > My question is, does it really matter whether I buy a 90mm or a 92mm
    > fan? I mean, if I'm wrong on the size, I'm only wrong by 2 millimeters.
    >
    > Daddy


    You'll probably be able to force it in there. I've done worse!
    Why are you upgrading the fan? Noise? I hate noisy towers that sound
    like a Learjet sitting on the tarmac waiting to take off.
    I wish somebody would apply that Dyson bladeless technology to PC case
    fans...
    Scratch that, there are bladeless fans for PCs but they're über expensive.
    Justin, May 2, 2011
    #9
  10. On 5/1/2011 6:52 AM, Ben Myers wrote:
    > On Apr 30, 11:16 pm, Daddy<> wrote:
    >> Ben Myers wrote:
    >>> On Apr 30, 11:30 am, Daddy<> wrote:
    >>>> I'm looking to upgrade the case fan in my Studio XPS 8100.

    >>
    >>>> The existing case fan is a Foxconn PVA092G12M. There's scant information
    >>>> available from a Google search; this is either a 90mm fan or a 92mm fan.
    >>>> My question is: Does it matter whether I use 90mm or 92mm? It's 2 lousy
    >>>> millimeters.

    >>
    >>>> I'm only asking because there are hardly any 90mm fans on Newegg - and
    >>>> none with 3 pins, but there are tons of 92mm models.

    >>
    >>>> Daddy

    >>
    >>> I don't understand "upgrade". A fan that blows more cubic feet per
    >>> minute? Or simply a replacement fan for one that does not work as
    >>> well any more? If the latter, just get another new one per its Dell
    >>> part number... Ben Myers

    >>
    >> Lol ... I knew somebody would eventually ask me "why are you even doing
    >> this?" And the answer is: I, uh, don't really have a good reason. I
    >> guess I'm trying for a little more quiet. I replaced Dell's stock video
    >> card, and that made my computer noticeably quieter. And case fans are
    >> cheap and easy to install, so I figured give it a shot. The Foxconn
    >> blows 45 CFM. If I can find something real quiet that blows as much air,
    >> I'll try it.
    >>
    >> My next project is an upgraded power supply. In a larger sense, all this
    >> is preparation for building my first ever computer.
    >>
    >> Daddy

    >
    > I forgot that the Studio XPS 8100 is a tower computer, not a laptop!
    > Your reasoning makes sense for a tower or desktop. It would be at
    > least mildly deranged to try to replace a fan with anything other than
    > a stock item for a LAPTOP.
    >
    > But pay attention to the connectors and wires for fan replacement in a
    > Dell... Ben Myers


    i believe that the 90mm vs 92mm issue is simply due to how they are
    measured, either by the outer dimension or by the mounting holes. in
    other words as far as i know they are the same and mount the same.
    also, i think the three pin fan connector on the 8100 is industry
    standard with the white wire on pin three. however may dell case fans
    are not wired the same as generic fans resulting in and error at start
    up about the fan not being detected. the size is not critical but the
    the wiring is.
    Christopher Muto, May 4, 2011
    #10
  11. Daddy

    Daddy Guest

    Christopher Muto wrote:
    > On 5/1/2011 6:52 AM, Ben Myers wrote:
    >> On Apr 30, 11:16 pm, Daddy<> wrote:
    >>> Ben Myers wrote:
    >>>> On Apr 30, 11:30 am, Daddy<> wrote:
    >>>>> I'm looking to upgrade the case fan in my Studio XPS 8100.
    >>>
    >>>>> The existing case fan is a Foxconn PVA092G12M. There's scant
    >>>>> information
    >>>>> available from a Google search; this is either a 90mm fan or a 92mm
    >>>>> fan.
    >>>>> My question is: Does it matter whether I use 90mm or 92mm? It's 2
    >>>>> lousy
    >>>>> millimeters.
    >>>
    >>>>> I'm only asking because there are hardly any 90mm fans on Newegg - and
    >>>>> none with 3 pins, but there are tons of 92mm models.
    >>>
    >>>>> Daddy
    >>>
    >>>> I don't understand "upgrade". A fan that blows more cubic feet per
    >>>> minute? Or simply a replacement fan for one that does not work as
    >>>> well any more? If the latter, just get another new one per its Dell
    >>>> part number... Ben Myers
    >>>
    >>> Lol ... I knew somebody would eventually ask me "why are you even doing
    >>> this?" And the answer is: I, uh, don't really have a good reason. I
    >>> guess I'm trying for a little more quiet. I replaced Dell's stock video
    >>> card, and that made my computer noticeably quieter. And case fans are
    >>> cheap and easy to install, so I figured give it a shot. The Foxconn
    >>> blows 45 CFM. If I can find something real quiet that blows as much air,
    >>> I'll try it.
    >>>
    >>> My next project is an upgraded power supply. In a larger sense, all this
    >>> is preparation for building my first ever computer.
    >>>
    >>> Daddy

    >>
    >> I forgot that the Studio XPS 8100 is a tower computer, not a laptop!
    >> Your reasoning makes sense for a tower or desktop. It would be at
    >> least mildly deranged to try to replace a fan with anything other than
    >> a stock item for a LAPTOP.
    >>
    >> But pay attention to the connectors and wires for fan replacement in a
    >> Dell... Ben Myers

    >
    > i believe that the 90mm vs 92mm issue is simply due to how they are
    > measured, either by the outer dimension or by the mounting holes. in
    > other words as far as i know they are the same and mount the same. also,
    > i think the three pin fan connector on the 8100 is industry standard
    > with the white wire on pin three. however may dell case fans are not
    > wired the same as generic fans resulting in and error at start up about
    > the fan not being detected. the size is not critical but the the wiring
    > is.


    I read elsewhere that the measurement (e.g., 92mm) is taken from the
    center of one screw to the center of either adjacent screw (not
    diagonally adjacent.) In any event, I am presuming that the tolerances
    here do not measure down to one or two millimeters, so I will buy 90mm
    or 92mm, whichever is the more suitable fan for me.

    The case fan in my Studio XPS 8100 uses a three pin connector. This
    means it reports its RPMs to the BIOS, but the fan speed cannot be
    controlled by the BIOS; that's where a fourth wire comes in.

    Something I've learned about replacing parts in an OEM computer: Most
    consumers who buy individual parts (beyond RAM or a hard drive) are
    either building their own gaming PC or doing substantial modding and/or
    overclocking, so replacement parts are largely marketed to this crowd:
    Power supplies have long connectors, case fans have bright LEDs, RAM has
    heat spreaders, etc. If all you want is to kick up your performance a
    notch or two, prepare to be overwhelmed. Anisotropic filtering? Sheesh!

    Daddy
    Daddy, May 4, 2011
    #11
  12. Daddy

    Sam Guest

    "Daddy" <> wrote in message
    news:iprvf0$l9v$...
    > Christopher Muto wrote:
    >> On 5/1/2011 6:52 AM, Ben Myers wrote:
    >>> On Apr 30, 11:16 pm, Daddy<> wrote:
    >>>> Ben Myers wrote:
    >>>>> On Apr 30, 11:30 am, Daddy<> wrote:
    >>>>>> I'm looking to upgrade the case fan in my Studio XPS 8100.
    >>>>
    >>>>>> The existing case fan is a Foxconn PVA092G12M. There's scant
    >>>>>> information
    >>>>>> available from a Google search; this is either a 90mm fan or a 92mm
    >>>>>> fan.
    >>>>>> My question is: Does it matter whether I use 90mm or 92mm? It's 2
    >>>>>> lousy
    >>>>>> millimeters.
    >>>>
    >>>>>> I'm only asking because there are hardly any 90mm fans on Newegg -
    >>>>>> and
    >>>>>> none with 3 pins, but there are tons of 92mm models.
    >>>>
    >>>>>> Daddy
    >>>>
    >>>>> I don't understand "upgrade". A fan that blows more cubic feet per
    >>>>> minute? Or simply a replacement fan for one that does not work as
    >>>>> well any more? If the latter, just get another new one per its Dell
    >>>>> part number... Ben Myers
    >>>>
    >>>> Lol ... I knew somebody would eventually ask me "why are you even doing
    >>>> this?" And the answer is: I, uh, don't really have a good reason. I
    >>>> guess I'm trying for a little more quiet. I replaced Dell's stock video
    >>>> card, and that made my computer noticeably quieter. And case fans are
    >>>> cheap and easy to install, so I figured give it a shot. The Foxconn
    >>>> blows 45 CFM. If I can find something real quiet that blows as much
    >>>> air,
    >>>> I'll try it.
    >>>>
    >>>> My next project is an upgraded power supply. In a larger sense, all
    >>>> this
    >>>> is preparation for building my first ever computer.
    >>>>
    >>>> Daddy
    >>>
    >>> I forgot that the Studio XPS 8100 is a tower computer, not a laptop!
    >>> Your reasoning makes sense for a tower or desktop. It would be at
    >>> least mildly deranged to try to replace a fan with anything other than
    >>> a stock item for a LAPTOP.
    >>>
    >>> But pay attention to the connectors and wires for fan replacement in a
    >>> Dell... Ben Myers

    >>
    >> i believe that the 90mm vs 92mm issue is simply due to how they are
    >> measured, either by the outer dimension or by the mounting holes. in
    >> other words as far as i know they are the same and mount the same. also,
    >> i think the three pin fan connector on the 8100 is industry standard with
    >> the white wire on pin three. however may dell case fans are not wired
    >> the same as generic fans resulting in and error at start up about the fan
    >> not being detected. the size is not critical but the the wiring is.

    >
    > I read elsewhere that the measurement (e.g., 92mm) is taken from the
    > center of one screw to the center of either adjacent screw (not diagonally
    > adjacent.) In any event, I am presuming that the tolerances here do not
    > measure down to one or two millimeters, so I will buy 90mm or 92mm,
    > whichever is the more suitable fan for me.
    >
    > The case fan in my Studio XPS 8100 uses a three pin connector. This means
    > it reports its RPMs to the BIOS, but the fan speed cannot be controlled by
    > the BIOS; that's where a fourth wire comes in.
    >
    > Something I've learned about replacing parts in an OEM computer: Most
    > consumers who buy individual parts (beyond RAM or a hard drive) are either
    > building their own gaming PC or doing substantial modding and/or
    > overclocking, so replacement parts are largely marketed to this crowd:
    > Power supplies have long connectors, case fans have bright LEDs, RAM has
    > heat spreaders, etc. If all you want is to kick up your performance a
    > notch or two, prepare to be overwhelmed. Anisotropic filtering? Sheesh!
    >
    > Daddy


    I replaced the case - processor fan in my xps 8100 with this one from
    Amazon.
    Sorry for the large text just pasted it from their site.
    Perfect fit, just cut the wires and used the old MB plug that lets the fan
    sensor work.
    Wire color matches, so it was no trouble.
    Sam

    Antec TriCool 92mm DBB Case Fan with 3-Spd Switch 3/4-Pin & 3-Pin Monitoring
    Sam, May 4, 2011
    #12
  13. Hi!

    > The case fan in my Studio XPS 8100 uses a three pin connector.
    > This means it reports its RPMs to the BIOS, but the fan speed
    > cannot be controlled by the BIOS; that's where a fourth wire comes
    > in.


    Actually, it can. The age-old trick (from the time that PCs started to
    include hardware capable of such things) is to drive the fan from a
    pulse-width-modulation controller. This works by varying the ratio of
    on time to off time...longer "on" pulses let the fan spin faster,
    while longer off pulses slow it down. Do this frequently enough and
    the illusion of "smooth" fan speed control can be maintained across
    the board.

    Dell doesn't do that *in most cases*. Instead, the Dell fans typically
    have a thermal sensing bulb poking out somewhere around the hub. This
    means the fan itself--and not any other part of the computer--controls
    its own operating speed.

    The newer four wire fans do things a little differently. The first
    three wires do as they've always done and serve to provide voltage
    input and tachometer output signals. The fourth wire actually accepts
    input data from the fan controller on the computer's mainboard and
    then the fan's electronics figure out how best to arrive at the
    desired rotational speed.

    The newest Dell systems (basically anything that is built around a BTX
    motherboard design) forgo the thermal sensing bulb and instead gather
    temperature from some point on the motherboard. Exactly where that is
    would be rather hard to say--apparently Dell uses custom chips (the
    function itself is embedded in the LPCIO IC) and apparently the
    internal workings of such chips are Great Secrets. (I actually asked
    SMsC about these chips and was told that they are protected under a
    nondisclosure agreement. Even their own employees cannot look up
    information on them. Evidently Dell--or whoever does the logic design
    of Dell's motherboards--thinks that a part used in basically every
    type of PC made in the recent past--is really something to keep a
    tight lid on. Whatever.)

    There are no obvious thermal sensors on the board. Most boards don't
    even seem to have places for them--the Dimension E521 board is a
    notable exception to this. It has solder spots for sensors.

    People who have managed to get some data on the SMsC LPCIO chips that
    Dell uses say that hardware monitoring and fan control aren't
    supported. That leaves me to guess that Dell uses the core temperature
    from the CPU to decide how hot the rest of the system is and then
    adjusts the fan speed accordingly, possibly by just writing the
    desired speed control data to the fan's control electronics over the
    fourth wire.

    I'd really like to know for sure. I've been contacted by people within
    Dell in times past--I wish someone would pick up on one of my posts
    along this subject and tell me what I'd like to know without all the
    red tape.

    William
    William R. Walsh, May 4, 2011
    #13
  14. Daddy

    Daddy Guest

    William R. Walsh wrote:
    > Hi!
    >
    >> The case fan in my Studio XPS 8100 uses a three pin connector.
    >> This means it reports its RPMs to the BIOS, but the fan speed
    >> cannot be controlled by the BIOS; that's where a fourth wire comes
    >> in.

    >
    > Actually, it can. The age-old trick (from the time that PCs started to
    > include hardware capable of such things) is to drive the fan from a
    > pulse-width-modulation controller. This works by varying the ratio of
    > on time to off time...longer "on" pulses let the fan spin faster,
    > while longer off pulses slow it down. Do this frequently enough and
    > the illusion of "smooth" fan speed control can be maintained across
    > the board.
    >
    > Dell doesn't do that *in most cases*. Instead, the Dell fans typically
    > have a thermal sensing bulb poking out somewhere around the hub. This
    > means the fan itself--and not any other part of the computer--controls
    > its own operating speed.
    >
    > The newer four wire fans do things a little differently. The first
    > three wires do as they've always done and serve to provide voltage
    > input and tachometer output signals. The fourth wire actually accepts
    > input data from the fan controller on the computer's mainboard and
    > then the fan's electronics figure out how best to arrive at the
    > desired rotational speed.
    >
    > The newest Dell systems (basically anything that is built around a BTX
    > motherboard design) forgo the thermal sensing bulb and instead gather
    > temperature from some point on the motherboard. Exactly where that is
    > would be rather hard to say--apparently Dell uses custom chips (the
    > function itself is embedded in the LPCIO IC) and apparently the
    > internal workings of such chips are Great Secrets. (I actually asked
    > SMsC about these chips and was told that they are protected under a
    > nondisclosure agreement. Even their own employees cannot look up
    > information on them. Evidently Dell--or whoever does the logic design
    > of Dell's motherboards--thinks that a part used in basically every
    > type of PC made in the recent past--is really something to keep a
    > tight lid on. Whatever.)
    >
    > There are no obvious thermal sensors on the board. Most boards don't
    > even seem to have places for them--the Dimension E521 board is a
    > notable exception to this. It has solder spots for sensors.
    >
    > People who have managed to get some data on the SMsC LPCIO chips that
    > Dell uses say that hardware monitoring and fan control aren't
    > supported. That leaves me to guess that Dell uses the core temperature
    > from the CPU to decide how hot the rest of the system is and then
    > adjusts the fan speed accordingly, possibly by just writing the
    > desired speed control data to the fan's control electronics over the
    > fourth wire.
    >
    > I'd really like to know for sure. I've been contacted by people within
    > Dell in times past--I wish someone would pick up on one of my posts
    > along this subject and tell me what I'd like to know without all the
    > red tape.
    >
    > William


    You analysis is very interesting, as usual.

    This is just anecdotal - based on my observations - but I do not sense
    that my case fan is varying in speed. But then, I don't really rock out
    my hardware in the first place.

    Daddy
    Daddy, May 4, 2011
    #14
  15. Daddy

    mm Guest

    On Wed, 04 May 2011 15:01:41 -0400, Daddy <> wrote:

    >William R. Walsh wrote:
    >> Hi!
    >>
    >>> The case fan in my Studio XPS 8100 uses a three pin connector.
    >>> This means it reports its RPMs to the BIOS, but the fan speed
    >>> cannot be controlled by the BIOS; that's where a fourth wire comes
    >>> in.

    >>
    >> Actually, it can. The age-old trick (from the time that PCs started to
    >> include hardware capable of such things) is to drive the fan from a
    >> pulse-width-modulation controller. This works by varying the ratio of
    >> on time to off time...longer "on" pulses let the fan spin faster,
    >> while longer off pulses slow it down. Do this frequently enough and
    >> the illusion of "smooth" fan speed control can be maintained across
    >> the board.
    >>
    >> Dell doesn't do that *in most cases*. Instead, the Dell fans typically
    >> have a thermal sensing bulb poking out somewhere around the hub. This
    >> means the fan itself--and not any other part of the computer--controls
    >> its own operating speed.
    >>
    >> The newer four wire fans do things a little differently. The first
    >> three wires do as they've always done and serve to provide voltage
    >> input and tachometer output signals. The fourth wire actually accepts
    >> input data from the fan controller on the computer's mainboard and
    >> then the fan's electronics figure out how best to arrive at the
    >> desired rotational speed.
    >>
    >> The newest Dell systems (basically anything that is built around a BTX
    >> motherboard design) forgo the thermal sensing bulb and instead gather
    >> temperature from some point on the motherboard. Exactly where that is
    >> would be rather hard to say--apparently Dell uses custom chips (the
    >> function itself is embedded in the LPCIO IC) and apparently the
    >> internal workings of such chips are Great Secrets. (I actually asked
    >> SMsC about these chips and was told that they are protected under a
    >> nondisclosure agreement. Even their own employees cannot look up
    >> information on them. Evidently Dell--or whoever does the logic design
    >> of Dell's motherboards--thinks that a part used in basically every
    >> type of PC made in the recent past--is really something to keep a
    >> tight lid on. Whatever.)
    >>
    >> There are no obvious thermal sensors on the board. Most boards don't
    >> even seem to have places for them--the Dimension E521 board is a
    >> notable exception to this. It has solder spots for sensors.
    >>
    >> People who have managed to get some data on the SMsC LPCIO chips that
    >> Dell uses say that hardware monitoring and fan control aren't
    >> supported. That leaves me to guess that Dell uses the core temperature
    >> from the CPU to decide how hot the rest of the system is and then
    >> adjusts the fan speed accordingly, possibly by just writing the
    >> desired speed control data to the fan's control electronics over the
    >> fourth wire.
    >>
    >> I'd really like to know for sure. I've been contacted by people within
    >> Dell in times past--I wish someone would pick up on one of my posts
    >> along this subject and tell me what I'd like to know without all the
    >> red tape.
    >>
    >> William

    >
    >You analysis is very interesting, as usual.
    >
    >This is just anecdotal - based on my observations - but I do not sense
    >that my case fan is varying in speed. But then, I don't really rock out
    >my hardware in the first place.


    If you have the Dell utilities (which I can get to by doing F12 on
    startup, and choosing utilities), one or more of them varies the fan
    speed. It says "running at slow speed", "running at high speed" and
    you can hear the difference. At least I can. :)

    >Daddy
    mm, May 5, 2011
    #15
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