| Limit | x86 | PPC | MIPS | SH-4 | ARMv4 | ARMv6 | ARMv7 |
|---|---|---|---|---|---|---|---|
| System RAM | 64 GB | 64 GB | 1 TB | 512 MBa | 4 GB | 4 GBb | 4 GB |
| Physical addressing | 36-bit | 36-bit | 40-bit | 32-bit | 32-bit | 32-bit | 32-bit |
| CPUsc | 32d | 32 | 32 | 2 | 1 | 1 | 4 |
| Virtual address spacee | 3.5 GB | 3 GB | 2 GB | 2 GB | 32 MB | 2 GB | 2 GB |
a 32-bit addressing gives 4 GB of space, but not all can be used for system RAM on some platforms. Some space is reserved for devices, and some platforms might impose other restrictions.
b The actual amount of RAM is determined by the system-on-chip implementation.
c The hardware might further limit the number of CPUs.
d If you plan to use more than 8 CPUs on an x86 platform, you must use the 6.5 or later version of procnto-smp with startup-bios or startup-apic.
e These are the absolute maximum limits for the virtual address space; you can reduce them by setting the RLIMIT_AS resource with setrlimit().