XPS Desktops

Last reply by 05-07-2022 Unsolved
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2 Bronze
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XPS 8940 and 8950, add pwm fans, control the speed with a hub/program

<Title was to long. DELL-Admin>

I have both XPS 8940 and 8950. I want to for both: 1.Add pwm fans 2. Control the speed with a hub/program. Is that possible?

To be exact:

Add PWM fans

  • Change the rear fans with respective sizes
  • Add 2 fans to the side panels
  • Change the front fan
  • Add a fan above at the front

Control the speed/rpms

  • By using a hub/controller
  • By using a program

Is this possible? What do i need to know?

 

Replies (2)
9 Rhodium
1095

One "gotcha".  Dell uses proprietary fans that interface with the BIOS.  Non-Dell fans can be used but because they are not sensed at POST (Power On Self Test) you will always get a fan failure notice and have to press an F Key to boot. 

I've seen references to Dell fan wiring and I remember something about non-ATX wiring so something else to look into. If you use a separate fan power distribution unit then this is not a problem.

There are other posts (threads) about fans in these models.  Do a search for them and see what was done or couldn't be done.

 

 



I am not a Dell Employee

Dell forum member since 2002

Dell Inspiron 15 Gaming 5577 Laptop

Home Built Desktop PC with Gigabyte Designare Z390,  i9 9900K CPU

Windows 11 64 bit Pro, 22H2, SSD drives. Cakewalk by BandLab and Studio One 4.6 Pro Recording Studio Software, MOTU Ultralite MK5 recording interface unit
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3 Argentum
1086

Surely you can, but there are prerequisites,
with SW control approach your application should be capable of:
1) reading temperature signal from CPU/VR + PCH and Ambient (can be done via relevant MB systems)
2) reading tachometer signal from CPU/Sys (et.c) fans (can be done via relevant MB systems)
3) sending control signal to right PWM systems (CPU/SYS/Chipset)
It's normally implemented via SuperIO controller (SMBus/I2C)
If your program can interact correctly with chip (read temps and tacho signals, write/set PWM override values) - then job is practically done, just install right fans/connectors/splitter and configure application.

Simple hardware approach might be much easier to implement without trying to programmatically find right port/address/offset/bits to read/write (or compatible application what could interact with your specific SuperIO controller). There are various 4-Pin PWM signal splitters available (tacho/sense read from single fan but PWM signal sent to multiple fans, aka power-share) for cheap (simple cable, with multiple outputs, or more complex circuit boards with additional power amplifiers/stabilizers, indicator panels, manual control resistors, separate thermal sensors and individual PWM chip, etc.).

As @fireberd has mentioned - Dell is very sensitive with installed devices compatibility-wise, once I've installed additional system fan and it has messed up whole balanced automatic regulation by internal logic, CPU temps started reaching 90 degrees without fan kicking-in to higher RPM (leading to thermal shutdowns), or CPU going into Turbo-Boost mode for prolonged periods of time without any need (e.g. without any system load), and whole range of other anomalies and instabilities, in the end I had to disconnect one of 4-pin connectors (Sense/Tacho pin) to get it back to normal operation without confusing internal PWM/thermal control logic coded by Dell.

--------------
I am not a Dell employee or affiliated in any other way,
just professional IT contractor and life-long technology enthusiast based in London/UK,
so do not mind sharing thoughts and ideas with community.
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