Is there a performance hit using 32 bit Linux on a 64 bit CPU?

Question

I'm running 32 bit Ubuntu 10.04 with 2GB RAM. Is my processor (AMD Athlon 64 X2) running sub-optimally? Given that a larger addressing space will make no difference to me (right now) would there be a performance gain or any other advantage to switching to 64 bit Ubuntu.

Answer 1

I cannot talk with figures, but as far as I know, 64 bit Ubuntu would run faster for really intensive calculations. Maybe for some multimedia... not really sure

For desktop use, probably you will not notice much difference. The biggest issue some time ago was the availability of flash 64-bit, some drivers which could behave different (i.e. if the were working just for 32-bits), etc

I also have an AMD Athlon 64 and I've tried a couple of times (four years ago) to use a 64-bit distro, and I found it much more displeasant (because of these bits) than the possible benefits I could achieve

Answer 2

Programs compiled for 64bit will run faster since the processor in 64bit mode expose more registers to the system. I'll illustrate with this pseudocode

X = 10
Y = 10
Z = 10

LOOP WHILE X > 0
{
  X=X-1
  Y=Y-1
  Z=Z-1
}

The above codes purpose is to subtract 1 from the value 10 until the value of X equals zero. If you for example had a processor with two registers it could hold the data for X and Y in those registers but would need to copy the registers to the main memory and retrieve value for Z from the main memory to be able to compute it. When X and Y are needed again it would need to do push out Z to the main memory and retrieve X and Y again. This would need to be done for each loop until X equals zero. If you have a CPU with more registers like eight for example the CPU could hold all the variables in the registers and would not need to access the main memory and thus avoiding a lot of processing and delays from the main memory who is a lot slower than the registers on a processor. For this reason almost all programs that are compiled for 64bit will run faster. This will mostly be noticeable on programs that does a lot of heavy computing as others have pointed out already. If this was hard to follow think of it as when your computer runs out of ram and needs to use the harddisk to hold data. Harddisks (and SSD's) are a lot slower than main memory. The reality is a bit different of course and performance gain/loss might not be noticeable depending on what you use your computer for. Generally speaking 64bit will be faster from a pure technical point of view. Hope this answers your question! :)

Answer 3

It depends on your exact computer configuration and workload. However, in the general case, you're not missing anything by choosing 32-bit over 64-bit for that configuration.

Answer 4

No real benefits for you, since you are not tackling large data sets or calculations.

There are some issues, as Dani mentioned, no 64 bit flash, and poor integration of other multi-media elements.

I have been running 64 bit Linux servers for 4 to 5 years at work with no real issues. I keep trying them at home and always go back to the 32 bit versions.

Answer 5

There should not be any performance difference. The only thing is that you cannot use much more than 3GB of RAM. You also won't be able to do some heavy duty math calculations.

Just keep in mind that even though you have a 64bit computer you can only use 32bit programs when using a 32bit OS.

Answer 6

There shouldn't be any significant performance difference since you don't currently have a problem with the 3 GB RAM limit of the 32 bit flavor of desktop Ubuntu. However, if you ever decide to use an emulator like Virtualbox or VMWare to run Windows programs on your system you might find yourself bumping up against the 3 GB limit in a hurry.

A few years ago 64 bit was a poor choice because of a lack of drivers for new devices. As of 2010 that problem has pretty much gone away. If anything, 32 bit drivers may start to get scarce a few years from now as the vast majority of hardware produced for desktop use is now 64 bit capable.

Hotei