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I'm converting old Windows desktop machines from 2005-2009 into cheap Ubuntu Linux servers. I want to know which ones can handle a 64-bit OS and which can't. I read that some x86 CPUs are 64-bit compatible. The question is how to check.

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Unless you need to handle more than 4gb of ram, 32 bit is prolly a better choice IMO, even with 64 bit capable systems. – Journeyman Geek May 22 '10 at 0:00
@The Journeyman geek -- I went 64-bit because of this quote from Ubuntu: "Unless you have specific reasons to choose 32-bit, we recommend 64-bit." – Bill Paetzke May 22 '10 at 0:32
up vote 11 down vote accepted

The definitive method:

  1. Download CPUZ
  2. Install and run it
  3. Check the "Instructions" value for EM64T (if Intel) or AMD64 (if AMD).

alt text

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Run this utility and check the field "Maximum Bit Length"; it will show either 32 or 64. This utility is mainly used for checking if your CPU supports hardware virtualization, but it can be used for this purpose as well.

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