To determine if a fan can use voltage control, check the specifications or manual for compatibility details.
To determine if a fan can use voltage control, check the specifications or manual for compatibility details.
Back not long ago, most MoBo headers except the CPU ones used 3 pin DC voltage. Today they’re mainly 4 pin but not PWM. These 4 pin connections usually manage both 4 pin PWM and 3 pin DC fans. While there are some technical benefits to PWM, I believe the extra costs aren’t justified. Particularly for fan control boards. For example, the Phanteks PCB converts a PWM signal into control for up to 11 fans. The benefit here is the ability to use extra power, whereas with DC fans you’re restricted by the header’s rating.
This perspective is flawed. The 3 pin fan headers offer no speed adjustment. They consist of a +12 volt supply, a ground reference, and one sensor pin. The sensor pin measures rotational speed by counting pulses every half rotation.
The 4 pin headers include an extra pin for PWM control. 3 pin fans work best with 4 pin headers, but the PWM pin is simply omitted.
Controlling speed for fans without PWM (3 pin chassis fans) is only possible by adjusting the DC voltage. Most fans assume a standard 12 volt supply and spin at the advertised speed, plus or minus some tolerance. For instance, Corsair SP 120 Quiet Edition fans run at the rated 1450 RPM on a 12 volt system.
The issue with DC control is that reducing the voltage reduces torque, which can cause stalling. If a motor stalls, it continues drawing current and may overheat. Each motor’s response to DC varies, but generally they’re meant to run at a set RPM with 12 volts. We don’t know how they’ll behave with less voltage.
PWM maintains constant maximum torque, just slowing it down. The motor runs slower but avoids stalling, unlike DC which can stall and overheat.
What’s particularly problematic about NZXT’s approach is the complete lack of speed monitoring in the Sentry 2. If a motor stalls, there’s no way to detect it except through physical inspection.
This would be a significant update for all my users and the broader community, as it's unusual to see such a setup. Right now, I manage 16 fans using my MoBo fan headers on the same motherboard. I'm curious about how your three-pin fan headers manage to control 16 fans across different speed ranges (326 to 850 rpm) on three separate channels, especially considering the other builds and projects you share each month.
Exactly... and this is precisely how the three-pin headers function. These headers are built into the motherboard. The BIOS or companion software (such as Asus fan Xpert2) manages the fans by adjusting voltage levels on these headers. It's a matter of interpretation—some sources say otherwise, but it's clear from experience that this setup works.
The distinction between PWM and DC voltage control can be likened to a playground scenario with spinning merry-go-rounds. DC variable voltage is like applying constant pressure to every bar, forcing them to spin faster or slower as needed. PWM control is similar to applying consistent pressure with varying intensity—adjusting the timing of pushes to achieve the desired speed.
Years ago, when DC variable control was simpler, a major issue was that low voltage wouldn't provide enough power to overcome a fan's inertia at slow speeds. Today, with advanced BIOS technology, the system can accurately test each fan and adjust accordingly, ensuring smooth operation across all speeds.
The MoBo utility helps pinpoint the exact stall point and sets precise control points, ensuring fans never stall under any conditions. This setup allows for smooth transitions between speeds and reduces noise, offering a more stable performance.
On my system, the AutoFan Tuning Mode starts at full voltage and gradually reduces it in 10% steps, recording actual RPMs. It identifies minimum, stall, and startup speeds and links them to voltage levels. This process ensures the fan never drops below 360 rpm at 330 rpm, maintaining optimal performance.
In my rig, the tuning mode sets a maximum fan speed of around 1238 rpm, though I rarely reach that. I maintain a temperature difference under 10°C across all conditions, with a peak of 850 rpm. Using three-pin fans instead of four-pin PWM reduces the speed at 300 rpm, but the utility sets a minimum of 326 rpm. I’m considering disabling them at higher speeds when idle, though they remain silent in that range.
Of course, this setup isn't available on basic $89 MoBo units. Speedfan could work, but without the auto-tuning and fine adjustments, you'd lose the benefits of precise control.
JackNaylorPE shared his insights on how his setup functions. He manages 16 fans using three MoBo fan headers on a single motherboard. He seeks clarification on how the three-pin headers manage fans across multiple channels—specifically between 326 and 850 rpm—on three different channels. He also inquires about the other builds and configurations they review each month.
He explains that the three-pin headers are part of the motherboard itself, and the BIOS or tools like Asus fan Xpert2 manage fan speeds by adjusting voltage at these headers. He notes that understanding this process can be tricky, especially when older guides don't reflect current tech.
He compares PWM and DC voltage control using a playground analogy: DC control is like forcing kids on a swing to keep it moving, constantly pushing until it spins faster. PWM is like always pushing hard or softly depending on the speed needed.
He mentions historical challenges with DC variable control, where low voltage at slow speeds failed to start fans. Modern BIOS now tests each fan and adjusts accordingly, ensuring smooth operation across the full speed range.
He describes his setup with detailed channel assignments and how he uses AutoFan Tuning Mode to monitor and adjust speeds based on temperature. He emphasizes the importance of setting appropriate control points and maintaining stable speeds without excessive noise.
He also warns that using 3-pin fans instead of 4-pin PWM can reduce maximum speed, though he avoids turning off fans at high speeds due to silence. He concludes that while the tech exists, it requires careful configuration and understanding of the system.
The argument centered on correctness rather than efficiency. Every detail aligned with the expectations of an engineering degree. The quoted post had no relevance to the NZXT controller; the discussion was focused on clarifying points about 3 and 4 pin fans. Expanding on their distinctions helps illustrate how 3 and 4 pin fans can be managed through MoBo headers. Many assume a 4 pin header automatically uses PWM, but in reality, 4 pin chassis headers control DC voltage, enabling speed regulation on PWM fans. Regarding efficiency, the perspective was inverted—while performance remains consistent overall, PWM tends to use more power at low RPMs. It should also be noted that motor noise like ticking, buzzing, or humming becomes noticeable at low speeds.
Thanks for the helpful information, JackNaylorPE and Pinhedd! I gained a lot from your posts.