Can you please give me link to those new reviews? I really want to see how A15 stack up to competition between 300-500RPM (that should be as low as 20% duty cycle)..
Sorry, don't have any review links for you, just my personal testing. Check your other thread you started, i posted some NF-A15 PWM runs on FanXpert2. In here ill post some others run to help explain what i posted above.
I must disagree. I own 2 ASUS motherboards ATM (H77 and Z77), and they all have same restrictions.
My experience is only with Asus Maximus VI Gene which is a Haswell Z87 motherboard that newer than yours, so idk for before models, but still i think should be similar.
CPU min PWM speed: 20%
On BIOS, all ROG Haswell motherboards are restricted to 40% on manual on CPU_FAN headers (this is intended by Asus), and in the preset "silent" is around 30% (there is no detail on the % that just interpolating).
Chassis min PWM speed: 60%
On Chassis is the same 60% as yours.
CPU min PWM speed: 20%
As i said before, FanXpert2 overwrites any restrictions on the bios, you believe is 20% because that what your fans are capable. Ill leave you a screenshot of the Noctua NF-A14 PWM ran on the CPU_FAN header under FanXpert2, in where you can see it can drop lower than 20%,
Chassis min PWM speed 40%
I also have plenty of PWM fans at my disposal, and I can confirm that chassis fans simply cannot be run at lower than 40%.
Here the concept is different, Asus motherboards only have 1 true PWM fan header (CPU_FAN and CPU_OPT that its a mirror of it), and the rest of headers even though they are 4pin they are not PWM headers, they are fake PWM header as some other members call them, recommended you read ASUS Z87-Deluxe fake 4-pin headers & other fan control info
. Ok so whats happening with your 40%..... well its simple, you are running fans that are design to be ran on PWM on Voltage control, and the fans are not design to work like that, this is the reason you think they are restricted to 40% when thats really the minimum voltage they will run (PWM is design to be run 12V not undervoltage).
Here is an example of a fan running lower than 40% on CHA_FAN2 header (fake PWM header, so its running on voltage control) on FanXpert2 (again depends on the fan)
For instance, I run Scythe Kama PWM at 280RPM via Chassis fan 2, I doubt I could achieve that with voltage control.
Scythe is wonderful with PWM, but its different, in some cases even PWM can reach lower on Voltage control, check SPCR Scythe Ashura CPU Cooler
, where you can see a PWM fan goes lower on voltage control than on PWM control, its all about how the fan was design,
The important thing you need to understand is how Asus works in BIOS and under FanXpert2, bios is restricted to what you see on the bios, and on FanXpert2 is unrestricted, the restriction are set by the fan capability to run under certain PWM signal or Voltage control, not by the bios nor fanXpert2 (it just determines it). The conclusion drawn from this is be careful what fans you run where, as not all headers are the same, nor the fans will behave the same.