How do PWM splitters connect PWM signal wires?

[BonzaiDuck]

I originally posted a similar question in "NVidia" -- asking for information about the fan wiring of MSI GTX 970 Gaming cards. At first I wondered if the plugs are standard PWM plugs, but without opening my case yet looking at review photos of the MSI card, I can see it is a proprietary wiring plug. It appears to have six or more possible pin positions.

It's my objective to use the PWM signal from one graphics card (of 2x SLI) for controlling a fifth fan to the four on the cards.

Since this is just a single wire for a signal, I'm curious as to how splitters such as the Swiftech 8W-PWM-SPL-ST, Akasa et al -- connect the PWM wires. Any of those splitters only require connecting the standard PWM plug and the signal wire alone to a motherboard fan port.

If all fan connectors at the split end of the splitters are connected at one point to that wire without any other components, I could simply tap in to the PWM signal of a graphics card and power the fifth fan from the PSU through the Swiftech splitter. Simply, I'd have a graphics card controlling three fans instead of the two in stock configuration, without drawing any more power from the GPU card than those original two fans. And, of course, I could add another fan or two . . . Maybe a total of two 80x15mm PWM fans.

 

[MrTeal]

The Swiftech splitter runs the 12V and GND from the SATA power connector, straight splits the PWM signal from the motherboard to the eight fan connectors, and returns the tach signal from fan on port one back to the motherboard. There's no logic or anything.

 

[BonzaiDuck]

The Swiftech splitter runs the 12V and GND from the SATA power connector, straight splits the PWM signal from the motherboard to the eight fan connectors, and returns the tach signal from fan on port one back to the motherboard. There's no logic or anything.

Basically, and as you may have given one, I was seeking a "second opinion" about the PWM signal wire.

When you say "straight splits the PWM signal," I assume you mean as follows in this example: You have eight fans; you therefore connect eight PWM wires to a single solder-joint leading to the single PWM pin connecting to the motherboard fan-port.

And the single PWM signal simply propagates along all eight paths?

If that is true, and IF I can identify the PWM wire at the MSI GTX 970 fan plug and port, then I should simply be able to tie all fan PWMs together, power the GPU fans from the same Swiftech splitter, and "good to go?"

I think I could do it either way: allow the GPU's original fans to obtain power from the card; tie in the PWM wire from an additional fan, and power the fan directly from the PSU?

 

[Cerb]

And the single PWM signal simply propagates along all eight paths?

Yes. The fan should terminate it, but it's only 25kHz, IIRC, so it can be a pretty dirty signal and still work fine.

Check your connection, definitely, but this could work:
http://www.amazon.com/Graphics-Cooling-Connector-Adapter-Conversion/dp/B005ZKZEQA

 

[BonzaiDuck]

Yes. The fan should terminate it, but it's only 25kHz, IIRC, so it can be a pretty dirty signal and still work fine.

Check your connection, definitely, but this could work:
http://www.amazon.com/Graphics-Cooling-Connector-Adapter-Conversion/dp/B005ZKZEQA

Are you sure that's not a 3-pin to 4-pin adapter?

The white plug is much smaller than the white port on the graphics card -- which is still wider in number of pins than the typical 4-pin PWM plug.

If I can just locate the PWM wire nearest the plug-connector for the GPU's fan-port, I should just be able to solder the PWM wire from a PWM splitter like the Swiftech, then re-insert the clip in the plug.

 

[mfenn]

Something to keep in mind is that PWM is just a duty cycle, it doesn't take into account any of the fan's other properties. Meaning, two different fans may have very different noise and airflow profiles at a 50% duty cycle.

 

[BonzaiDuck]

Something to keep in mind is that PWM is just a duty cycle, it doesn't take into account any of the fan's other properties. Meaning, two different fans may have very different noise and airflow profiles at a 50% duty cycle.

Y-Yup!! I'm investigating options with this. I already have a few fans as candidates in the event I need an extra fan or two in the project. Possibly -- one or two 80x15mm Noctua PWM's.

 

[Cerb]

Are you sure that's not a 3-pin to 4-pin adapter?

Yes, it's 4-pin. Not all graphics cards use the same connector, though. You can get an adapter for some different ones, but for the life of me, I cannot recall the website that sells them. If the PWM pin is just a nominal 25kHz PWM signal, though, you can just use a matching connector.