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Should I install a 32 or 64 bits version ?

Asked by , Edited by vrkalak [ Moderator ]

What are the pros and cons of installing a 32 bits vs a 64 bits version of Debian on the same PC ? 
Is Squeeze different than Lenny for that matter ?

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3 answers

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liwfi [ Editor ]

64-bit works better if you have more than 4 gigabytes of RAM. Other than, there is no real difference for most people.

There certainly are other differences, of course. For example, the 64-bit mode has more CPU registers, which means some computationally heavy code runs faster. 64-bit programs also need a bit more memory for bigger pointer values. However, for most people, these don’t usually matter. If you have a specific application that you worry about, try it both ways and see which is faster for you.

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r murphy
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Additionally with the 32bit compatibility libraries you can usually also run 32bit binaries on the 64bit system, thus I think there is no real value to run the 32bit system.

schamane
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Good point: It won’t be long and 64 bit will be the default. So why not switch today!?

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1

adam.trickett [ Editor ]

I’ve run all my AMD64 boxes in 64-bit mode since Sarge. The advantages are that if you have lots of RAM then the flat memory model is quicker than the alternatives, which is a big win if you are doing lots of e-commerce or database type stuff. It’s unlikely that a typical home user would notice.


The way the CPU runs is also cleaner and the there are other register advantages that could in theory make code run faster. It is probably that in 64-bit mode you would get a few percent more performance but not a huge amount and you may not notice it. Some things apparently run a lot faster even if you are not taking advantage of the RAM issue.

In the days of Sarge lots of things wouldn’t run in 64-bit mode, so you had to run stuff in 32-bit mode with some kind of shim, now we are on Lenny this is less of a problem – there is even a beta 64-bit Adobe Flash plugin.

If you have a 64-bit CPU, unless there is some very specific 32-bit software you want to run that can’t be made to run on a 64-bit system, then there is no obvious reason not to install the 64-bit version.
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pehjota [ Editor ]

liwfi and r murphy covered this pretty nicely. But to add to it, if you plan on keeping your system around through 2038, you'll want to use a 64-bit OS. Otherwise, come January 19, 2038, your software clock may show December 13, 1901. More information: http://en.wikipedia.org/wiki/Year_2038_problem


I don’t think there’s any difference between Lenny and Squeeze in architecture support; AMD64 has been an official port since Etch. And Debian lists some advantages that the 64-bit architecture has over the 32-bit i386:
    • no memory segmentation into low and high memory
    • up to 128TiB virtual address space per process (instead of 2GiB)
    • 64TiB physical memory support instead of 4GiB (or 64GiB with the PAE extension)
    • 16 general purpose registers in the CPU instead of 8
    • gcc defaults to SSE2 math instead of 387 FPU
    • gcc omits frame-pointers by default at -O2
    • compilation time optimization uses a common base for AMD64/EM64T instead of legacy i386 cruft
    • memory pages are not executable by default

I would say use the AMD64 port if you have a 64-bit processor, for future-proofing and the possibility of performance enhancements.
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