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Mixing types of RAM is not always healthy, but I am curious as to what happens (if anything) when mixing CPU types in a system.

Example:

  • 8-Core 2.0Ghz Magny Cours CPU in socket 0
  • 12-Core 2.0Ghz Magny Cours CPU in socket 1

Is there anything "bad" about this? Do the CPUs have to match, or is merely a Good Idea™?

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up vote 7 down vote accepted

Simply won't work correctly. They MUST match. Even if you somehow managed to make them work, I predict bad, and unexpected things.

The reason can be relevant to microfirmware code, being uploaded to CPU inner storage, when BIOS POST does the patching of silicon bugs. The patching routine can decide to check only 1st CPU stepping and apply same patch to 2nd cpu without check. Hipotetically. But who knows what is happening in POST really.

You'll have to go to the manufacturer's documentation (for both CPU and motherboard) to find the limitations. Such drastically different CPUs as you list are unlikely to work properly. In the past, CPUs that were identical other than the exact stepping level sometimes even weren't able to be used together. "It depends".

You need support from the bridge chips, the motherboard, and the OS. All of these would have to work in concert to work with the imbalance of the CPUs. They'd have to go through programming and intensive testing for many combinations for very little gain (over an equal CPU config).

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Care to explain why that's the case? –  Ivo Flipse Jun 2 '11 at 18:50
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The reason can be relevant to microfirmware code, being uploaded to CPU inner storage, when BIOS POST does the patching of silicon bugs. The patching routine can decide to check only 1st CPU stepping and apply same patch to 2nd cpu without check. Hipotetically. But who knows what is happening in POST really. –  user27803 Jun 2 '11 at 19:37
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@Warren - Why does KCotreau's post the EXACT same answers from other people? –  Ramhound Jun 7 '11 at 18:02
    
@Ramhound - because I added them all together, as per the FAQ –  warren Jun 7 '11 at 19:57
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@Shinrai - I'd argue that it is exactly the purpose of being able to edit answers into the best one possible –  warren Jul 1 '11 at 22:59
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You'll have to go to the manufacturer's documentation (for both CPU and motherboard) to find the limitations. Such drastically different CPUs as you list are unlikely to work properly. In the past, CPUs that were identical other than the exact stepping level sometimes even weren't able to be used together. "It depends".

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My guess is no.

What do we need to get it to work? You need support from the bridge chips, the motherboard, and the OS. All of these would have to work in concert to work with the imbalance of the CPUs. They'd have to go through programming and intensive testing for many combinations for very little gain (over an equal CPU config). I'm guessing it won't work.

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