I'm learning about ubuntu, but I do not know the ubuntu 13.04 Ram and CPU support up to how much??? hope you help me
As far as maximum CPU support, I don't think it exists, but there might be a limit on the number of CPU's it can handle.
If you have more than 3 GB RAM in your computer, you don't have to pick 64-bit Ubuntu for making full use of your RAM. The 32-bit Ubuntu automatically installs a PAE kernel. The kernel is the core of the operating system. A PAE kernel can address up to 64 GB of RAM.
A PAE 32-bit kernel therefore isn't bothered by the 32-bit memory hole, which plagues old-fashioned 32-bit kernels.
The kernel used by the 32-bit Ubuntu can recognize up to 4GB of memory, although the amount of usable memory available to the user is slightly less than this. A kernel recompiled with PAE enabled can use up to 64GB of physical memory.
The kernel used by 64-bit Ubuntu can theoretically recognize up to 17.2 billion GB of physical memory, but this is subject in practice to hardware limitations. Current AMD64 implementations allow for up to 256TB of physical memory. Current Intel 64 implementations allow for up to 1TB of physical memory.
Of course, you have to have a 64-bit architecture to use a 64-bit OS. But even if you don't have a 64-bit architecture, Linux can take advantage of your memory if you don't mind compiling your own kernel.
Just to give an idea, I'm running Ubuntu 13.04 32bit on a machine with Core2Duo CPU, and 4GB RAM, and if you just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:
sudo dmidecode -t 16
it will show you the maximum amount of RAM that it can handle. (system Specific)
One has to distinguish between what Ubuntu supports out of the box, and what it can support when one uses a custom kernel.
There are numerous features in the Linux kernel that can be tweaked at compile time. For the default, generic kernel, the Ubuntu developers choose values they think are appropriate.
Regarding RAM, this means, that at least before 12.04 on a 32bit Ubuntu by default one could only use 4 GB of RAM, since in the generic kernel the PAE feature was disabled. Nevertheless, one can install a different kernel image (for instance linux-image-server) that allows to access as much RAM, as the (nominally 32bit, but usually 36bit big) address register of the CPU can handle (usually 64 GB).
I don't know about 12.04 and newer (I use the 64bit version), but I assume that on those PAE is enabled, so it should support 64 GB if the CPU does (please, can anyone running 32bit Ubuntu check if PAE is enabled and post a comment?). Supposedly, on 64 bit one can use the whole 64bit address range, meaning 16 Exabytes.
Regarding the number of CPUs, the Linux kernel can (at least on AMD64) handle up to 512 CPUs, yet in the generic kernel for Ubuntu (64 bits, 12.04) the maximum number of CPUs is configured 256.
Ubuntu installs the kernel configuration file in /boot/config-, so one can always look up the current settings there.
The maximum ram supported for ubuntu 32 bit is 64gb(with the PAE kernel extension included with 12.04 and later). 64 bit Ubuntu, I think it's something along the lines of 1 tb (1024 gb). As for processors, I don't think there's an upper bound to what it can support in terms of power. Just make sure you're using a common processor architecture such as i386 or amd64. Since Ubuntu runs on high powered servers with extremely powerful processors and large amounts of ram, I cannot see the average user topping the limit.
to my knowledge there are no limits, since Ubuntu is also used for large servers etc. and Linux in general runs supercomputers I think there should be no problem. If you have more that 4 gb of RAM you probably should choose the 64-bit version.