IO APIC & PAE, do I really need either?

[loukingjr]

I've had VirtualBox for quite awhile and always meant to ask this but never have. In Linux guests, is there any compelling reason to have IO APIC or PAE enabled? I am never going to use more than one core since I only have two, I am never going to make a guest using more than 1024 MBs of ram since I only have 3 GBs and do nothing with Linux other than make themes. I was just wondering if any Linux guests might be looking for them to be enabled or perhaps run better.

thanks

[Sasquatch]

There isn't a real reason to use them, other than some features needs it. SMP and 64 bit mode need IO APIC and some Linux kernels require PAE (mostly server build kernels). Even so, PAE isn't required for the generic desktop kernel, even if you have more than 1024 MB of RAM. It's only required if you end up with 4 GB of RAM or more so it can allocate that. Else it's stuck at 3,5 GB tops, but it's usually less.

[loukingjr]

There isn't a real reason to use them, other than some features needs it. SMP and 64 bit mode need IO APIC and some Linux kernels require PAE (mostly server build kernels). Even so, PAE isn't required for the generic desktop kernel, even if you have more than 1024 MB of RAM. It's only required if you end up with 4 GB of RAM or more so it can allocate that. Else it's stuck at 3,5 GB tops, but it's usually less.

Ok thanks. I wasn't sure but as I said, I figured I didn't really need them. I just thought if I didn't need them, is just extra code to slow a guest down. Although, even though it's mentioned IO APIC may slow a guest down, I never really noticed anything enabled or not. I also only have tried one 64 bit guest and really didn't see any advantage for what I do with Linux.