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HP Z800 Would not boot after a restart. Forced to reset CMOS and drain power.

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I often work with Z800 workstations. I upgrade them with x5670 processors and populate it with more RAM, for nice workflow. I have noticed one strange thing, which at first I thought was the issue with the fact that they are upgraded with the different processors. but turns out that very often this happens with the original processors too. 


SO the issue is: after a restart computer would not boot. It powers on, fans start spinning louder then usual after half a minute, HDD LED will not show any progress, no beep codes, and nothing on displays. Solution for now that worked (but not for long) is when I force to power it off, drain the power and reset the CMOS. After that procedure It would start up and sometimes after 2nd or 3rd restart it would not boot again.


I have 3 towers now with GTX 570 

48GB of RAM (6x 8GB 133MHZ Registered RAM, installed in 1,3,5 and 1,3,5 dimms)

Processors: Dual x5670 and one tower with Dual E5640

Windows 7 OS.

BIOS v3.61 (which is latest)

Power supplies: 850W. 


If anyone had same issues, please share how you battled. 

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you might have a failing/bad motherboard/power supply, while the no boot unless you reset the cmos with power disconnected for a while can happen once in a blue moon, constant no pwr on problems point to a failing part


you can try swapping the power supply between one that has a problem with one that does not and note the results


also poor power to the computers (low voltage, noisy pwr line, bad grounding) can cause issues so try swapping the entire system to a location/socket  that did not have a issue with a z800 connected to it


last, the 850 watt supply is NOT RECOMENDED for high power CPU'S HP plainly states that you require the upgraded supply when running a dual high power xenons or have a system with multiple hard drives/addin cards


the hp supply is a multi rail unit, as such it is possible to overload a single rail and still be within the 850 watt limit


you may be overloading the rail they supplies the power to the cpu's, you can remove one and see if that helps


or install the upgraded supply

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I was having  issues with my Z800 - it would power down/cycle on start, or restart intermittently . Replacing the CMOS battery fixed all issues .  Perhaps to be expected - these are old machines (and batteries)  at this point, but still awesome when they are up and running..I was experiencing:


-starting the computer and would shut down...

-shutting down after up fo a bit...

-slow startup...


I probably would have diagnosed it earlier if I had not paid atention to the "BIST" diagnostic codes that lead me to believe that my power supply was faulty...


I _HIGHLY_ recommend replacing your CMOS battery before trying other and EASY...I cant believe that I bought 2 power supplies (one that exploded after 2 days)  trying to solve this problem....(and as you may know - Z800 power supplys are not resonably priced...especially when the signal codes from the "BIST" tech tells you to replace the power supply when you only need a new battery...


The helpful link that lead me to the solution also  recommended new thermal compound for my processors....looked at/repalced on one, not convinced this was related...  Hoping this saves you the time and trouble 

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