Cpanel, 64 bit and RAM....your thoughts?


Sep 9, 2001
I am currently looking at setting up a server with the following specs:

Dual Xeon 3.2
RedHat Enterprise Linux 4 - 64 bit
4x400 GB SCSI drives in Raid 5

My main concerns are as follows:

1) Will Cpanel run stabily on a 64 bit system and be able to address and make use of the larger amount of RAM. I first and foremost want to ensure the server would be stable and the software run properly.

2) Will PHP, Apache and Perl all function properly and be able to use the larger amount of RAM.

3) For any 32 bit applications that are running will they only be able to access 4 GB of RAM rather than the 8GB? If this is the case and the above apps only use the 4 GB of ram rather than 8 GB would it not be worth having this much RAM.

As an option I could enable Physical Addressing Extensions (PAE) and recompile the Linux kernel however I am not familiar with this enough to know if there are any drawbacks to doing this or if the server will become unstable.

If anyone can share their thoughts on this it would be appreciated.


Well-Known Member
Feb 8, 2003
I will recommend you to check the compatibility of php modules on a 64bit system. Easyapache does not compile all the php modules on a 64 bit system successfully.

bcmath calendar ctype curl exif ftp gd gettext mbstring mcrypt mysql overload pcre posix session sockets standard swf tokenizer xml Zend Optimizer zlib [Zend Modules] Zend Extension Manager Zend Optimizer

Check the compatibility of above modules.



Well-Known Member
Verifed Vendor
Jun 15, 2002
Go on, have a guess
The addressing of the additional memory is really down to the OS/Kernel not the individual applications.

If you go with the 64bit OS you should expect to have library problems. All the x86_64 OS is is essentially a rebuild of the 32bit code and you'll probably gain very little in terms of performance over the 32bit OS. The main issue of contention is with perl modules from cpan which mostly don't look for 64bit libraries, so unless they're either linked into the 32bit library directories or the 32bit version is also installed, you can regularly get perl module failures at both installation and run time.


Nov 30, 2004
Spam Assassin

Well, the things that do take advantage of the 64 bit have been worth it for me. My old machine had a slower processor and memory bus speed, but I got a 10x faster average time with the 64 bit machine in the average times reported by SA. I was amazed. I have had no problems with Fedora 4 64 bit at all. Dual Opertron was probably way overkill, but hey, I'm a hardware geek.

I was going to put some log bits here for comparison, but it doesn't appear the cpanel box logs the same level of detail for spamd. The gateway does have the numbers I remembered. When I was using the 64 bit for the same purposes, the decimal point just moved over one place. YMMV