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Do I need more RAM for programming if I switch to a 64 Bit OS?

I haven't done any proper clinical analysis but the first time I booted a 64 bit version of Linux some years ago I was surprised at how much memory programs were consuming, but of course I had not actually memorised the previous values I had observed.

Am I imagining things or is there a calculable difference in RAM usage between 32 and 64 bit version of the same programs? I can't be bothered to dual boot a 32 bit version to find out but I'm just curious if it was some kind of placebo effect :-)

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barrymac
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2 Answers2

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Technically yes, but the difference is marginal at worst. If it matters, then you don't have enough memory in the first place.

Darth Android
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    The difference isn't always marginal. For example, I measured that a 64-bit Firefox (3.0 IIRC) used more than twice the amount of memory as a 32-bit Firefox (both running on a 64-bit system, so if anything the 32-bit one was at a disadvantage for not being able to share as many libraries with other running applications). – Gilles 'SO- stop being evil' Jul 27 '11 at 22:58
  • @Gilles That would be something application-specific, and there are a huge number of variables in a complex application like that which doesn't mean that the 64- to 32-bit comparison is apples to apples until you control some of those variables. You'd have to compare a fresh install of 32-bit firefox with a fresh install of 64-bit firefox, including no extensions, empty cache / history/ etc., and a blank startup page to get any sort of meaningful results. – Darth Android Jul 28 '11 at 14:00
  • IIRC I used the same version of Debian Iceweasel in both cases, with the same profile. I think the profile was my usual profile and I loaded my session at the time. Technically the difference might have been due to a particular extension or history entry or whatnot, so maybe it doesn't apply to all varieties of apples, but it was an apples to apples comparison. – Gilles 'SO- stop being evil' Jul 28 '11 at 14:50
  • it is not minimal at all – Francesco Mar 18 '14 at 12:32
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Yes, you will use a lot of memory more. Read the example of Gilles. Firefox/Chrome 64bits is the better example for this question in a desktop computer.

amd64 is a architecture superior to x86 but only if you computer has the hardware necessary. Not only the processor, you will need more RAM, more processor cache (very important), etc.

If you need a computer for scientific applications, convert/edition video or any application mathematically intensive, use 64bits. For a "office computer" for now is better to use x86.

Rufo El Magufo
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    Thank you for pointing out the processor cache, I hadn't thought of that! Very important when considering 64bit on mobile machines – barrymac Jul 28 '11 at 13:37
  • You should always get the biggest available cache. That's not 64-bit specific. Also, what do you mean by "more FSB" ? (PS, AMD processors never had a FSB, and Intel got rid of the FSB 4-ish years ago). – Darth Android Jul 28 '11 at 13:57
  • You're right about FSB, I confused terms. But AMD and Intel had FSB http://en.wikipedia.org/wiki/Front-side_bus . About the cache, I mean the binaries for amd64 need more cache than the same software in x86 version. – Rufo El Magufo Jul 29 '11 at 00:18