Max. number of CPUs supported under Ubuntu

Yes sir... If you are using a linux server installation, on a:

1.Intel x86:
Maximum CPUs: 32 (including logical CPUs)
Maximum memory: 64GB
Maximum filesize: 8TB
Maximum filesystem size (ext3) 16TB
Maximum per-process virtual address space: 4GB

2.AMD64/EM64T:
Maximum CPUs: 64
Maximum memory: 128GB
Maximum filesize: 8TB
Maximum filesystem size (ext3): 16TB
Maximum per-process virtual address space: N/A

These are standard max limitations whereas Linux cluster systems can scale up to 1024 CPU's..

And Maximum number of processes Linux 2.6 kernel can handle is:
Maximum number of threads: 32000
Maximum number of threaded processes: 32000
Maximum number of processes: 32000

For up to date information please refer Linux Kernel documentation located at /usr/src/linux/Documentation.

Hope this information helps...
Regards,
Bhavani Shankar.

But specifically how many is Ubuntu's OS capable of supporting?

I'm going to guess it would be the standard number (32 for Intel, 64 for AMD), but I'm not going to say that unless I have some amount of proof.

Thank you for your answer, Bhavani. I read something along those lines, but it's Linux not Ubuntu specific (I don't know much about Linux yet).

Oh, and it's ma'am, not sir! :-D

OK!!! Sorry for that... 32 and 64 means the word length of a computer ie a single word can be represented by 32 bits or 64 bits.. And has no connection with the no of processors supported...
And each and every os has to be based on a program called as a kernel, which coordinates the hardware and software by making the address spaces in memory and Input/output for various devices and so on.. Thereby the os locates the various devices in the computer and Linux os's run on a program called the linux kernel and Ubuntu is a linux os.. To summarize every linux os is based on the linux kernel.
Regards,
Bhavani Shankar.

I hope it answers your doubt!!!