Techy computer question regarding supplying power to case fans
#1
I'm in the process of re-locating a mobo/cpu to a new case, and I'm not quite sure how to handle adding extra case fans. The old case had no fans, but the new one will have at least two. The motherboard is a ASUS F2A85-M which only has a single 4-pin case fan slot (unless I'm blind).

As I see it, my options are to use a y-splitter to the case fan slot on the motherboard, or to just connect the case fans directly to the power supply via the molex connectors. Are there pros or cons for either option? Am I overthinking this?
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#2
(05-30-2015, 03:56 AM)DeeBye Wrote: I'm in the process of re-locating a mobo/cpu to a new case, and I'm not quite sure how to handle adding extra case fans. The old case had no fans, but the new one will have at least two. The motherboard is a ASUS F2A85-M which only has a single 4-pin case fan slot (unless I'm blind).

As I see it, my options are to use a y-splitter to the case fan slot on the motherboard, or to just connect the case fans directly to the power supply via the molex connectors. Are there pros or cons for either option? Am I overthinking this?


I'd connect the case fans to the power supply.
"I may be old, but I'm not dead."
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#3
(05-30-2015, 04:32 AM)LavCat Wrote:
(05-30-2015, 03:56 AM)DeeBye Wrote: I'm in the process of re-locating a mobo/cpu to a new case, and I'm not quite sure how to handle adding extra case fans. The old case had no fans, but the new one will have at least two. The motherboard is a ASUS F2A85-M which only has a single 4-pin case fan slot (unless I'm blind).

As I see it, my options are to use a y-splitter to the case fan slot on the motherboard, or to just connect the case fans directly to the power supply via the molex connectors. Are there pros or cons for either option? Am I overthinking this?


I'd connect the case fans to the power supply.
I'd 2nd that motion... The only reason to use the MOBO fan connector may be if you want the MOBO to vary the speed of the fan depending on the temp of the CPU. This is often a sound issue (slower = quieter). Aka... ASUS Fan Xpert 2
”There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy." - Hamlet (1.5.167-8), Hamlet to Horatio.

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#4
I agree with both posters above me. In regards to your mobo, it should have a CPU fan and perhaps a slot for the side chassis fan, but like others have said, just use the extra psu plugs, and if you need splitters, the fans draw very little power so it should be fine. Remember to get proper air flow going for computer zen Heart .
"The true value of a human being is determined primarily by the measure and the sense in which he has attained liberation from the self." -Albert Einsetin
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#5
(06-02-2015, 09:24 PM)kandrathe Wrote:
(05-30-2015, 04:32 AM)LavCat Wrote:
(05-30-2015, 03:56 AM)DeeBye Wrote: I'm in the process of re-locating a mobo/cpu to a new case, and I'm not quite sure how to handle adding extra case fans. The old case had no fans, but the new one will have at least two. The motherboard is a ASUS F2A85-M which only has a single 4-pin case fan slot (unless I'm blind).

As I see it, my options are to use a y-splitter to the case fan slot on the motherboard, or to just connect the case fans directly to the power supply via the molex connectors. Are there pros or cons for either option? Am I overthinking this?


I'd connect the case fans to the power supply.
I'd 2nd that motion... The only reason to use the MOBO fan connector may be if you want the MOBO to vary the speed of the fan depending on the temp of the CPU. This is often a sound issue (slower = quieter). Aka... ASUS Fan Xpert 2

Not true, there are other reasons to use onboard fan connectors, specifically to not draw additional power from the PSU and instead use the power going through the board to supply the power to the fan.
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Einstein said Everything is Relative.
Heisenberg said Everything is Uncertain.
Therefore, everything is relatively uncertain.
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#6
(06-04-2015, 06:07 AM)Lissa Wrote: Not true, there are other reasons to use onboard fan connectors, specifically to not draw additional power from the PSU and instead use the power going through the board to supply the power to the fan.
I guess. It is a small draw anyway, but if it were a toss up, I'd rather not add to the mobo's PS burden (or the graphics cards). In a multi rail system, you'd most likely put the fans on the 5v rail. GPU and Mobo are on the 12V rails.
”There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy." - Hamlet (1.5.167-8), Hamlet to Horatio.

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#7
(06-04-2015, 04:02 PM)kandrathe Wrote:
(06-04-2015, 06:07 AM)Lissa Wrote: Not true, there are other reasons to use onboard fan connectors, specifically to not draw additional power from the PSU and instead use the power going through the board to supply the power to the fan.
I guess. It is a small draw anyway, but if it were a toss up, I'd rather not add to the mobo's PS burden (or the graphics cards). In a multi rail system, you'd most likely put the fans on the 5v rail. GPU and Mobo are on the 12V rails.

Again, yes and no. While the overall amperage is small, it's pulling it from the 5V line which normally doesn't have a whole lot of amperage to supply.
Sith Warriors - They only class that gets a new room added to their ship after leaving Hoth, they get a Brooncloset

Einstein said Everything is Relative.
Heisenberg said Everything is Uncertain.
Therefore, everything is relatively uncertain.
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#8
(05-30-2015, 04:32 AM)LavCat Wrote: I'd connect the case fans to the power supply.

Haha, I'm so late at this stuff. I do shift work and I'm trying to do this rebuild with my son when we are both awake and together. We finally got around to messing with the rebuild last weekend, and connected the front case fan to the power supply. I connected the rear 120mm case fan directly to the single motherboard case fan connector. As far as I can tell, power is fine.

I hit a pretty major roadblock though.

Everything worked when I powered up the rebuilt computer, except I did not get any video. Neither the GPU nor the onboard APU sent any signal to the monitor. My first thought is that it's a AMD/nVidia driver conflict. I didn't disable nor remove the AMD onboard graphics or drivers before installing the nVidia GPU and I think the system just freaked out and said "no video for you!".
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#9
If you're getting no video from the time you power on, it's not a driver conflict as the OS isn't loaded. I would try removing the video card, connect the monitor to the onboard and see if you get video. If you do, try reseating the nVidia card again and try starting up again to see if you'll get video from either on start up.
Sith Warriors - They only class that gets a new room added to their ship after leaving Hoth, they get a Brooncloset

Einstein said Everything is Relative.
Heisenberg said Everything is Uncertain.
Therefore, everything is relatively uncertain.
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#10
DeeBye: Is that the card I sent you? Perhaps give it a visual inspection for any loose components on the boards. Sometimes international shipping can be a bit rough.
"What contemptible scoundrel stole the cork from my lunch?"

-W.C. Fields
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