PS3 Fan Tech Info
The PS3 has a somewhat unique fan arrangement in several ways. The most noticeable design feature is that it is a centrifugal fan, instead of the traditional axial fan like you will find in the PS2 and most desktop computers. A less noticeable feature is the fan speed control, which allows the fan to run quietly when system temperatures are low, and to run faster when the system deems it necessary. This is the feature that I am concerned with, and that this blog is dedicated to.
Fan speed control is nothing new, and PWM (the method used by PS3 fans) is nothing new either. Even monitoring fan speed without a tach signal (as the PS3 does) has been done quite often in the past. However, the PS3 uses fans that have the same oddball PWM control scheme as you would find in a Dell server. Because of this, normal "off the shelf" PWM fan controllers either don't work or can only function to lower speeds.
In theory, there should be no need to modify the fan speed. The mechanical and electrical design of the systems is just fine...but the firmware isn't. In order to minimize noise, Sony wrote the firmware to run the fan slow, even as the system is overheating. The fan only speeds up once the system is so hot that damage has already been done. The most common heat-related failure is the YLOD or "Yellow Light of Death". It is caused by the solder cracking after repeated heating/cooling cycles. The more severe the temperature difference between fully cool and fully hot, the more severe the damage. It should be noted that YLOD is a somewhat misleading term; depending on model and the specific solder point(s) that break, the YLOD does not always have a yellow light.
I should layout the basics of how the PWM works in the specific case of the PS3. I will not go into the specifics of how PWM works in general...wikipedia does that just fine.
There seem to be 3 generations of fan for the PS3 line. They all run on 12V DC power, and they are all PWM controlled.
The first generation appears to only have been in the initial launch model 20GB models and some 60GB models. While the airflow and manufacturer are different than the second generation, the control signals are the same.
The second generation can have 15 or 19 blades, and they seem to always come from Delta (although they may have used other brands built to Delta specifications as some point). These fans work on a 5.0v pulse by default, but also work fine with 3.3v pulses. In my testing, I have never encountered a PS3 mainboard that will run one of these fans beyond 66.6%, even when doing the "Fan Test". The fans are rated to run at 100%, so my fan controller design allows you to run the fan faster than the fan test does. With the exception of launch models, all fat PS3s seem to have this fan generation.
The third generation is the slim PS3 fan. This fan works essentially the same as the second generation, but uses 3.3V pulses by default and should not be used with 5.0 pulses. The PS3 slim does have the ability to run the fan past 66.6%, the highest readings I have found were about 92%, this is the same as the top speed limit for my fan controller (at least on the versions safety limits).
To summarize:
1st Gen: Works on pulses anywhere from 2.6V to 6.0V. Built-in minimum speed. [thanks to wizdumb for the image that let me confirm that 100%]
2nd Gen: Works on pulses anywhere from 3.3V to 5.0V.
3rd Gen: Works on 3.3V pulses only.
All of my fan controller designs run use 3.3V pulses. Readers in some countries might find it difficult to source 3.3V voltage regulators, and thus might choose to use a 5.0V regulator instead. This is fine for the fats (not the slims), it does not make the fan run faster or slower than it could have at 3.3V; the voltage change really has no effect on the fat models. However, 5.0V should NEVER be used with a PS3 slim.