Can Ubuntu read (and use) more than 4 GB of RAM?

[alicson]

It might be evident just based on my question that I'm completely new to Linux, but
can Ubuntu make use of more than 4gb of RAM? If possible, how would I set that up?
I'm on a PC (dual core 2 processor).

[Was very disappointed to learn that Windows has no concept of RAM above (and barely) 4gigs.. Might also be true with Linux, but would think there's more flexibility there..?]

[hyper_ch]

the 64bit version can... the 32bit is stuck at 3gb I think

I think also Windows 32bit is stuck at 3gb

[aaaantoine]

The 32-bit version of both Ubuntu and Windows can use a maximum of 4GB. Ubuntu might be able to use 64GB (I once read that modern 32-bit processors are actually more like 36-bit processors), but beyond 4GB you're better off with the 64-bit version of Ubuntu anyway.

Also, there is a 64-bit version of both Windows XP and Vista. For a small fee you can order the software discs and use them with your current license.

[hyper_ch]

well, there are hardly any 64bit applications for Windows as far as I know...

[insane_alien]

64-bit can read far more than 4GiB of RAM(i'm running on 8 just now)

32-Bit will be limited to 3.7GiB(the other 0.3GiB is reserved for external devices like PCI and kernel operations)

the kernel can be recompiled with the 'big memory' module which uses a block model to address the RAM and can read more than 4GiB thoug hthis is rather innefficient and slightly slower.

in your case i would recommend moving to 64-bit it will cause the least problems.

[alicson]

So 64-bit Ubuntu should recognize 6 GB of RAM without additional setup/actions?

And there's no conflict with having 32-bit XP Pro and 64-bit Ubuntu (dual-boot) on one machine, right?

Thank you all for your responses.

[Inxsible]

Originally Posted by alicson So 64-bit Ubuntu should recognize 6 GB of RAM without additional setup/actions? And there's no conflict with having 32-bit XP Pro and 64-bit Ubuntu (dual-boot) on one machine, right? Thank you all for your responses.

Yes. Its the architecture that defines how much memory can be used, because the more the memory you need more bits to address those huge blocks of memory. 32 bit processors can handle only 2^32 bits = 4294967296 bits of addressing. if you notice that's close to 4GB (just a bit less since 1KB = 1024bytes and NOT 1000 bytes). That's why a 32 bit processor can only access 4GB or less. 64 bit processors however can access 2^64 bits = 18446744073709551616 bits ~= 16 exabytes ~= 16 billion GB

No. None whatsoever. I have a dual boot of Vista 32 bit and Gutsy 64 bit

[P4man]

Originally Posted by Inxsible Yes. Its the architecture that defines how much memory can be used, because the more the memory you need more bits to address those huge blocks of memory. 32 bit processors can handle only 2^32 bits = 4294967296 bits of addressing. if you notice that's close to 4GB (just a bit less since 1KB = 1024bytes and NOT 1000 bytes). That's why a 32 bit processor can only access 4GB or less. 64 bit processors however can access 2^64 bits = 18446744073709551616 bits ~= 16 exabytes ~= 16 billion GBt

you are probably deliberately simplifying, but the above is incorrect. Since the Pentium Pro, our cpu's have been able to address 36 to 48 bits of RAM (depending on the cpu). Do the math, its faaar more tthan 4GB. They have, however, been limited to 32 bit virtual address space (per process). Until AMD64 came along that is.

So there could have been Pentium Pro servers with say 64 GB RAM and a 32 bit OS. These worked fine if they ran many small workloads. That same machine would have been able to process the exact same workload with just 1GB RAM, only MUCH slower. But such a machine could never load a 4GB app (/process) even if it had 64GB RAM; A 64 bit machine with a 64 bit OS would be able to load that 4+ GB workload even if it had only 1 GB physical ram.

Capiche ?

[Inxsible]

Originally Posted by P4man you are probably deliberately simplifying, but the above is incorrect. Since the Pentium Pro, our cpu's have been able to address 36 to 48 bits of RAM (depending on the cpu). Do the math, its faaar more tthan 4GB. They have, however, been limited to 32 bit virtual address space (per process). Until AMD64 came along that is. So there could have been Pentium Pro servers with say 64 GB RAM and a 32 bit OS. These worked fine if they ran many small workloads. That same machine would have been able to process the exact same workload with just 1GB RAM, only MUCH slower. But such a machine could never load a 4GB app (/process) even if it had 64GB RAM; A 64 bit machine with a 64 bit OS would be able to load that 4+ GB workload even if it had only 1 GB physical ram. Capiche ?

I know. When I posted, i meant per process addressing. Sorry I didnt mention it earlier. My bad.

[markyb86]

Originally Posted by P4man you are probably deliberately simplifying, but the above is incorrect. Since the Pentium Pro, our cpu's have been able to address 36 to 48 bits of RAM (depending on the cpu). Do the math, its faaar more tthan 4GB. They have, however, been limited to 32 bit virtual address space (per process). Until AMD64 came along that is. So there could have been Pentium Pro servers with say 64 GB RAM and a 32 bit OS. These worked fine if they ran many small workloads. That same machine would have been able to process the exact same workload with just 1GB RAM, only MUCH slower. But such a machine could never load a 4GB app (/process) even if it had 64GB RAM; A 64 bit machine with a 64 bit OS would be able to load that 4+ GB workload even if it had only 1 GB physical ram. Capiche ?

He was not incorrect, those servers probably had several processors, and the Server operating system dictates whether or not they can handle that kind of load just like xp can use 4gb and server 2003 can use 64gb, but thats only with 8 processors. Yeah it was a 32 bit OS but it wasnt end user