Question about molex and PSU (Newbie to System Building) (Need a solution!)

[SGilley]

Hello,

I just purchased the APEVIA X-DREAMER4 case from Newegg (link: http://bit.ly/16dduhB) and a Rosewill PSU (http://bit.ly/YsxGVz). I know close to nothing about System Building (these came in a combo) but I was reading reviews for the case and it said that all the fans were molex, and I was wondering if I will have to buy adapters for them. Thanks!

 

[SGilley]

I forgot to mention that I ordered this is in a DIY PC combo.

 

[Paperdoc]

You might need an adapter, depending on your choices.

First, a bit of background information. You may have read of "3-pin fans" and "4-pin fans". The 3-pin ones have 3 connections to the mobo - +12 VDC (varying for speed), Ground, and Speed Pulse signal. That last one is for a signal generated by the fan motor and sent back to the mobo to be monitored. 4-pin ones have a fourth wire to use a different type of speed control system fed from the mobo. YOUR case fans, however, are neither of these, because they will not have a Speed Pulse Signal output line. This means no matter how you connect them, they will not provide a speed readout via the mobo. They are closest to 3-pin fans in that they use a +12 VDC and a Ground line for power.

Now, IF you plan to power the case fans from mobo SYS_FAN output ports (so that the mobo's automatic fan speed controllers can control the fans according to case internal temperatures) you WILL need 2 adapters to convert from a mobo 3-pin ouput port to a fan 4-pin Molex input. In this choice, the mobo ports MUST be able to operate for 3-pin fans. That is, they must control fan speeds by varying the DC voltage supplied to the fan (4-pin fans don't vary this voltage; they provide a different control signal on the 4th pin). Thus these fans' speeds CAN be controlled by the mobo. They will not send their speed signals to the mobo - in fact, in some mobos, you can go to a place in the BIOS Setup screens and tell the mobo to Ignore the SYS_FAN speed signals since there are none with your kind of fan. NOTE that control of the fan speed does NOT need the speed signal to work, because the control system is based solely on measured TEMPERATURE, not speed.

Alternatively, you can not connect these fans to the mobo at all. They are fitted with 4-pin male (with pins) Molex connectors (even though they only use 2 wires from that), and you plug those into mating female connectors from your PSU. Then they will run at full speed all the time, because the PSU's output is always 12 VDC on the line used. Your PSU has 2 such output connectors, called "Peripheral Connectors", and they are about 3/4" wide with 4 round holes in a single row. However, sometimes you need one of these to provide power to older types of peripherals. So you can choose to buy a simple 2-from-1 splitter that will convert one PSU output to two (for your fans) and leave one PSU output unused. The PSU Molex outputs can provide much more power that 2 fans need, so connecting several fans to one such output is entirely OK.

 

[SGilley]

You might need an adapter, depending on your choices.

First, a bit of background information. You may have read of "3-pin fans" and "4-pin fans". The 3-pin ones have 3 connections to the mobo - +12 VDC (varying for speed), Ground, and Speed Pulse signal. That last one is for a signal generated by the fan motor and sent back to the mobo to be monitored. 4-pin ones have a fourth wire to use a different type of speed control system fed from the mobo. YOUR case fans, however, are neither of these, because they will not have a Speed Pulse Signal output line. This means no matter how you connect them, they will not provide a speed readout via the mobo. They are closest to 3-pin fans in that they use a +12 VDC and a Ground line for power.

Now, IF you plan to power the case fans from mobo SYS_FAN output ports (so that the mobo's automatic fan speed controllers can control the fans according to case internal temperatures) you WILL need 2 adapters to convert from a mobo 3-pin ouput port to a fan 4-pin Molex input. In this choice, the mobo ports MUST be able to operate for 3-pin fans. That is, they must control fan speeds by varying the DC voltage supplied to the fan (4-pin fans don't vary this voltage; they provide a different control signal on the 4th pin). Thus these fans' speeds CAN be controlled by the mobo. They will not send their speed signals to the mobo - in fact, in some mobos, you can go to a place in the BIOS Setup screens and tell the mobo to Ignore the SYS_FAN speed signals since there are none with your kind of fan. NOTE that control of the fan speed does NOT need the speed signal to work, because the control system is based solely on measured TEMPERATURE, not speed.

Alternatively, you can not connect these fans to the mobo at all. They are fitted with 4-pin male (with pins) Molex connectors (even though they only use 2 wires from that), and you plug those into mating female connectors from your PSU. Then they will run at full speed all the time, because the PSU's output is always 12 VDC on the line used. Your PSU has 2 such output connectors, called "Peripheral Connectors", and they are about 3/4" wide with 4 round holes in a single row. However, sometimes you need one of these to provide power to older types of peripherals. So you can choose to buy a simple 2-from-1 splitter that will convert one PSU output to two (for your fans) and leave one PSU output unused. The PSU Molex outputs can provide much more power that 2 fans need, so connecting several fans to one such output is entirely OK.

Thanks for the feedback! I looked at the reviews once again, but I decided to purchase a Corsair PSU as I heard that Rosewills are not as good. I will keep this in mind about the multiple ways of connecting the fans and will buy the adapters necessary. Thank you!