Can 32 bit Linux handle 4GB of RAM?

I have read in numerous posts that 32 bit Windows Vista can only handle 3 GB of RAM. Do 32 bit Linux distros have this limitation as well?

 

That depends on your motherboard and chipset.

 

32-bit supports 4 GB, but the kernel consumes 1 GB.

Loads of good info here: http://www.spack.org/wiki/LinuxRamLimits

"the short answer is that it's not possible with a 32bit operating system. the maximum size for a single process is: 4gb - 1gb (reserved for the kernel) - "overhead" where overhead is size of the executable plus the size of any linked libraries etc." - Adam Shand

 

The 32-bit RAM limitation isn't only limited to Windows, but to all other 32-bit operating systems as well.

 

The RAM limitations are based on the nature of 32-bit OSs regarless of who makes the OS, by definition 32-bit will never be able to use 4gb of RAM effectively.

 

Thanks a lot guys. Thats exactly the info I wanted to know. I have a AMD 64 in my desktop and used 64 bit Kubuntu for a while but went back to 32 bit since I had issues with FireFox and Flash. Not sure the current status of 64 bit distros.

 

It depends on whether your chipset supports PAE or not. Because I have 5GB of RAM on my dual Xeon (32bit P4-era) machine, and it's all accessible:

Code:

david@Brain:~$ free
             total       used       free     shared    buffers     cached
Mem:       4802064     999336    3802728          0     147676     643720
-/+ buffers/cache:     207940    4594124
Swap:      2072376          0    2072376

There can be a slight performance penalty, and for only 4GB, it's not really a good idea to worry about it. You'll still be able to access 3.7GB or so of the physical RAM. If you had more than 4GB, then you could consider either installing the server kernel or compiling a custom kernel (what I have to do) so that you can use all your RAM.

 

More importantly, it depends on whether or not you enable PAE.
Far from all software works well with it, and in general, it's not really suitable for "normal use".

For most people, it'll be a bad idea to enable PAE, even if the chipset supports it.

 

It's pretty much invisible to the software. It creates a latency accessing memory when the OS has to move the "window", though. Each app still gets the 4GB of address space it's used to, and still addresses it with 32bit pointers. And it depends on your chipset as to whether you CAN enable it

I've played Doom3, most of the shooter games I can find in Ubuntu (Warsow, Alien Arena, etc.) and even run games like Starcraft under Wine on my system with PAE enabled, and haven't run into any problems. It's only under Windows that PAE really causes issues at the application level.

To test if your system is capable of PAE:

Code:

david@Brain:~$ cat /proc/cpuinfo | grep pae
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe pebs bts sync_rdtsc cid xtpr

Like I said, there is a bit of a performance hit as well as a more complex configuration, and for 4GB of RAM it's almost certainly not worth it. But if you have more than 4GB and need to run in 32bit for some reason, it's worth it.