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I just got an old IBM x445 with 4xXeon and 32GB RAM home. I happily put in Win2008R2 DVD but got a bit surprised when it said the system only has 32-bit CPU. A quick Google confirms that.

What does a 32-bit system use more than 3-4GB RAM for? Can the OS run 10 4GB processes? Or does the process need to have explicit PAE support?
What can I do with this box? I want to host virtual servers on it. Will it work to run 32-bit Win2008 Datacenter and allocate 4GB to each virtual server?

Edit: Rephrased as some answers pointed in a bit newbie direction.

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4 Answers 4

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In case you want to read up on the theoretical aspect of this question, the reason you can have up to 64GB of RAM on a IA32 server is PAE. It's basically a trick on the page table level to make use of the 4 extra address lines available since the Pentium processor.

The Wikipedia page says you need a Datacenter or Enterprise edition of Windows Server to be able to use 32GB of memory.

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What does a 32-bit system use more than 3-4GB RAM for?

Running things that benefit from lots of RAM, like database servers. (This was needed in high load environments before 64bit systems became generally available.)

Will 32-bit Windows be able to use >4GB RAM?

The right edition, with the right applications: Yes. It'll need to be a Server edition that supports PAE memory (not sure if Standard would: you might need Enterprise).

Plus something like SQL Server that will make use of PAE (again check details).

What can I do with this box?

Run a database server, or other specialised software written to make use of paged memory extensions. You'll also need to ensure all device drivers are PAE aware (most aren't). Such servers tended to be used with fat support contracts running validated hardware and software in data centres.

Today: get a 64bit capable box. All but the most basic of machines can handle more than 4GB RAM without needing special care to ensure everything works.

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MSDN Article for PAE is msdn.microsoft.com/en-us/library/aa366796%28VS.85%29.aspx –  Ryaner May 2 '11 at 17:19
    
Note: PAE is a really ugly hack to make more than 4GB work. There were compromises made to get it working, it should not be compared to 64-bit processor + OS + Apps. –  Chris S May 2 '11 at 17:25
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@ChrisS: PAE is rather like the dancing bear: it isn't about how well it dances, but that it dances at all. Overall I expect the effort to get such a server working and keep it running would be better spent on new hardware and a lot less effort. –  Richard May 2 '11 at 17:27

In the unix world, the typical use is that since 32 bits only serves to address 4G of RAM, the kernel can partition things up so that each process is able to use up to 4G of RAM, so on a system that beefy you could have up to 8 different apps all using the max 4G before it started to crunch. No individual process will be able to use more than that at once, but for a server where lots of things are doing lots of jobs, it makes sense.

Sorry I can't say how Windows will deal with that.

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Windows Server 2003, Datacenter Edition 32-bit supports up to 128GB of RAM.

Windows Server 2008 Enterprise and Datacenter Edition 32-bit support up to 64GB of RAM.

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