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At work I recently received a Z800 Workstation. The fans in this computer are running very loud and we have not been able to quiet it down.


I have updated the BIOS to the latest (03.57 Rev. A) and set to defaults. This didn't seem to change anything.


I have also installed the SpeedFan utility and tried to use that to slow down the fans. It does not seem to be able to impact the fan speeds at all.


In the BIOS, I see this information regarding temps and fan speeds.


* CPU 0 = 32C
* CPU1 = 32C
* Ambient = 0C
* Memory = 36C


Fan speeds showed this:
* CPU0 = 1109 rpm
* CPU1 = 0
* Memory = 785 rpm
* Chipset = 0
* Chassis = 4150rpm
* PCI = 0


The sound coming from the workstation is not like a fan is broken or going out. It is just simply like the fans are working extra hard keeping things cool. It sounds like I'm sitting in a data center.


Is there anyway to have the fans come on an off as needed or slow down? Is there some HP utility that I'm not seeing?


Any ideas would be appreciated.





P.S. This thread has been moved from Workstations - Itanium-Based, hp9000, Visualize to Workstations - z series, xw series, and legacy x and w series. - Hp Forum Moderator

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in BIOS, under Power - Thermal - Fan Idle Mode - what is it set to?

If to default (minimum) - then something is wrong with the system. Perhaps the ambient sensor is broken. Pretty sure it shouldn't be zero.
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I wondered if the Fan Idle Mode setting was supposed to do something. It appears to be at the minimum. When I change it, the fans speed up slightly then settle back to their 'normal' level. Doesn't seem to matter what setting I put it on the fans end up running the same.

I guess we'll figure something is broke.
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Hi, I recently bought a used z800. I have the same issue of fan noise. Its running at a very high speed and gives loud noise.


Did you solve the issue ? If so can you help me out ?

HP Recommended

geez this system set on minimum fan speeds in BIOS is really loud (when you set it to max - its like starting jet)

unfortunatelly speedfan doesnt work


I just unplugged all the fans except CPU one - the drawback is I have to press F1 every time I boot

stupid BIOS doesnt allow pass errors (it displays fan missing and waits for F1)

I dont understand why HP does not allow change it


HP Recommended

Here is fan info that applies to many of the HP workstations.  With the xw6600 and xw8600, and the Z400/600/800 workstations you can go into BIOS and see some of the fan speeds and temperatures.  Things vary a bit by workstation but the basics are found under the BIOS first File tab, under System Temperatures.  Here is for a Z600 I just checked:


CPU0          28 C

CPU1          28 C    (this is a motherboard sensor.... there is no second processor installed)

Memory    752 RPM

Chipset     2962 RPM    (this is a small high rpm fan that I often use a 4-wire PWM speed reducer on)

Chassis    1142 RPM   (one fan from the pair of rear chassis fans is reported on by BIOS)

PCI             934 RPM     (this is the front bottom fan, and not present in some xw workstations.  Seems required for Z ones.


Some non-HP hardware monitoring software can see sensors and fans that the HP BIOS does not report on.  HWMonitor, the latest free version, from CPUID.com, is my favorite.  There is also SpeedFan which has been able to see some sensors in the past that HWMonitor could not.  The more recent HP workstations have not had their sensors work as well with these two programs than the older xw workstations did, but there is a new version of HWMonitor just out, 1.26, which is detecting on this Z600 better than ever before.  The JPEG is attached below.


A critical piece of information is in the forum here elsewhere..... if the ambient air sensor (thermisitor) temps are detected as being too high or low the motherboard responds in a crisis mode and ramps up many fan speeds.  So, if you see an ambinet temp, for example, of 0 or of 115 C the motherboard will ramp up the speeds radically.  In HWMonitor that ambient temp us usually by the heading TMPIN2.  The fix is to replace the front cable assembly, which has the ambient air temp thermisitor built into it.  That sensor has gone bad if it is reporting significantly too high or low.


Remember that you can find used HP 92x92x25mm PWM fans pretty easily on eBay with two plug ends.... the white PWM ones that are what you are used to seeing with a little ridge down the middle face of the white end, and the brown PWM ones that HP uses for its Chassis fans which do not have that ridge.  In most of the xw6600 workstations I have worked with the memory and the two rear chassis 92mm fans are identical, except for their fan plug end types, and part numbers.  Later Z workstations have more complex plug end wiring, too.


Another cause of fan speed rampup is if a defective fan is in place.  For example, a HP PWM fan that has lost its PWM feedback either electronically or by bad wire.  Then the fan sees full 12VDC and no PWM throttle, and runs too fast.  Or, someone else has put in an incorrect fan.


The fan speeds above for this Z600 are generally what you should be seeing in your HP workstations, not in the 4500 RPM range.


Here is what the latest HWMonitor 1.26 saw on this properly functioning Z600 this morning, and I'll check on a Z620 soon also.  You can see that this version of the free HWMonitor is reporting out significantly more sensors than the BIOS is:


UGH Z600 HWMonitor 1.26.jpg



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I had the same exact problem.  Apparently, I had opened the case and closed it again without paying attention to close it tightly.  Since the Aluminum cover has complex surfaces, it seems you would need to take extra care that the cover is tightly snug against the case. Otherwise, a protruding small cylinder on the cover inside, would not push against a sensor inside the case to “tell” the workstation that the cover is closed.  In other words, take your workstation to a very well lighted room and make sure that there is no opening in the seam between the cover and the case.  If you see an opening in the seam make sure you push the cover against the case and you should hear a click of the lock.  Also, make sure that when you remove your hand there will be no opening in the seam.  That should solve your CPU’s  fan noise.   

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Some of these workstations were provided with the option to have a sensor installed that could tell if the case cover was closed or not, but those are rare.  I personally have never seen one on any of the xw or Z workstations I have worked with, but there are standard wires available to plug one of those in.


I had no idea that one of the features of that sensor might be that the fan speeds would go way up if the cover was not fully closed. 


So, for future readers, don't expect to find one of those sensors if you look, but if you do find one then make sure the cover is fully closed...... and failure of that sensor might even cause a ramp up of fan speeds even if the cover is closed.  It should be easy to unplug that sensor if it is in place.

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I have the same problem. I finally find out the problem. It's because the power supply cause the noise!  the power supply is funtional, but something in it is going bad.  You can put your ear on the power supply at almost rear, you heard the noise exactly as the loud noise. 


Change the power supply then every thing is fine. 



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YES, The fans are loud. The noise really use to bother me before.


However latley I have become hard of hearing so the fan noise does not bother me any more.....

Alex Hernandez
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