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Possible Duplicate:
Ubuntu 64-bit vs 32-bit


I currently run a Ubuntu system with 32 bit but I have 4 GB of RAM. As I have heard only 3 GB are used. In the recent time I'm seeing that I need more memory. The question is: Should I change to Ubuntu 64 bit? I heard that with a 64 bit system you need twice as much memory as with a 32 bit system so effectively I would have less memory?! In the near future I plan to upgrade my RAM to 6 GB or 8 GB but this wouldn't pay off significantly if this was true, right?

I have seen related questions on this topic, but they weren't that specialized on the memory issue... But if I understand it correctly it also depends on the Applications used: On my computer a lot of memory is used by Web browsers (Chrome, Firefox). But I also use Eclipse and often use VMWare (Windows XP with 1 GB) That sometimes really slows down my system, in particular the VM becomes slow... And I am now working on a project that needs Hadoop, this might also need a reasonable amount of memory...

So my question is: Does it pay of to switch to Ubuntu 64 bit? Or would I need at least 8 GB or 10 GB of memory to have a reasonable payoff?

Thanks, Philip

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marked as duplicate by nhinkle, Sathya, Nifle, random Dec 5 '10 at 1:18

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

This has been discussed extensively before on SuperUser: Ubuntu 64-bit vs 32-bit, 32-bit vs. 64-bit systems, Search. – nhinkle Dec 4 '10 at 20:38
what are the reasons to switch? – kagali-san Dec 4 '10 at 21:04
up vote 1 down vote accepted

It pays to switch.

See the following questions on SU:

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Thanks, this was really enlightening! – Philip Dec 4 '10 at 20:53

In my experience the idea that a 64-bit install takes twice as much memory is rubbish.

What you really need to figure out is if the 3GB limitation is really a problem for you. A technology called Physical Address Extension allows a 32-bit processor to address up to 64GB of RAM. It may not be enabled in Ubuntu by default, but Ubuntu is uses a kernel with support. Check out this article:

Your operating system is currently addressing 3.37GB (give or take) of your RAM, so by switching to 64-bit or enabling PAE you'd gain something like 768MB.

Of course, there's a performance benefit to a 64-bit operating system that means the upgrade is worth it for non-memory reasons.

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Thanks for your answer. The point with the performance benefit is interesting, I almost have forgotten about that one. Regarding PAE: I had read that PAE give you trade offs regarding performance because the OS cannot use the whole memory at the same time but has to switch address space. – Philip Dec 4 '10 at 20:42
That's a widely held myth about PAE, that is something like bank-switching. It is not. Address translation with PAE is much like it is without PAE, but with one additional "layer" of page table lookup added. It's especially amusing to see people disparage PAE that way, and then recommend a 64-bit OS. Address translation on x64 is like address translation on x86 with PAE, but with yet another layer of page table lookup added! (two layers on x86 w/o PAE, three with PAE, four on x64.) – Jamie Hanrahan Aug 3 '14 at 21:53

I dont think the memory usage will increase with CPU architecture. The 64bit Linux is capable of handling morethan 4GB of memory. But the 32bit kernel is also able to handle that with PAE ( Physical Address Extension ). The memory usage in the system depends on the application that you are using. Also before switching to 64bit, you need to check that the applications that you are using are available in 64bit architecture.

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Thanks for your answer. Actually I am thinking about switching to 64 bit since years. The main argument was for me the thing with 64 bit App support. But now all apps I am using are available for 64 bit (even Flash...) so I guess I have now no reason to not switch to 64 bit... – Philip Dec 4 '10 at 21:16

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