I have Dell Precision T5400 workstation with two Intel Xeon processors. One a x5450 (quad core) and a e5450 (quad core). Both CPUs are recognised in the BIOS

My BIOS where you can see CPUs
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I can not even install Windows with 2 processors installed. First I have to pull out one of them, then install windows. If I put the second processor back in I get error 'Multi processor not supported'.

I can work around that by booting with a single CPU and in System configuration -> Boot advanced options select the checkbox 'Number of processors' and set it to four (4 because that is about processor cores).

After that I can start windows and it wil use a single CPU.

Note that Device manager see 8 cores (2 CPUs).
Task manager see just 4 cores (in performance tab).

My system data
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I installed Windows 10 Pro (updated from 8.1 Pro), and OS see just one processor.

Does anyone knows what is the problem?

  • "I should not even to install Windows with 2 processors ..." What? – Ramhound Apr 6 '16 at 14:40
  • Windows 10 Professional fully supports systems with 2 CPUs installed. Systems running 64-bit version support 256 cores. – Ramhound Apr 6 '16 at 14:43
  • It was impossible to install Windows (8.1 Pro) while PC have 2 CPUs. On installation start it shows error message and did it again and again till I didnt unplug one CPU. – orthodox4ever Apr 6 '16 at 14:43
  • @Ramhound I read it also, but as you see in BIOS - there are 2 CPUs, Also in device manager there are 8 processor drivers, but system work with just one. – orthodox4ever Apr 6 '16 at 14:46
  • @Ramhound When I want to install Windows from DVD, I see Windows logo for a few seconds and after that I get light blue screen with error message 'Your pc ran into a problem and needs to restart. We're just collecting some error info, and then we'll restart for you'. That message was shown for just few milliseconds so I had to record a video to see that message :) – orthodox4ever Apr 6 '16 at 14:58

The problem was been that I had 2 different CPUs, one is X5450 and another is E5450. When I changed one of them, to be the same, problem is fixed.

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