How to download
You may choose to download everything in one go or you may choose to download only what is necessary.

If you have chosen the latter, download README file first.

Step 2. Choose the kernel you wish to tweak and download appropriate patch:
vanilla kernels 2.4.0 - 2.4.10
vanilla kernels 2.4.11 - 2.4.12 (remember not to use 2.4.11 kernel)
vanilla kernels 2.4.13 - 2.4.14
vanilla kernels 2.4.15 - 2.4.17
vanilla kernel 2.4.18
kernel 2.4.19-pre10-ac2 (with Ingo Molnar scheduler)
RedHat 7.2 default kernel (2.4.7-10)

Step 3. Download the cap utility

How to install
Installation procedure is fully described in README file.

How to use
Boot your system using patched kernel. Use it just as any other kernel.
If you wish to limit CPU usage for any task, run cap command:
$ cap <task pid> <CPU percentage>

You can also consult appropriate manpage for more details.

Please note that only superuser can increase the limit. Remember that the CPU limit is inherited by task's children, just like any other limit.