MemoryError, can I use more?

Laszlo Nagy gandalf at
Sun Feb 14 12:28:59 CET 2010

2010.02.13. 17:40 keltezéssel, Diez B. Roggisch írta:
> Am 13.02.10 17:18, schrieb Anssi Saari:
>> Nobody<nobody at>  writes:
>>> A single process can't use much more than 2GiB of RAM without a 
>>> 64-bit CPU
>>> and OS.
>> That's not really true. Even Windows XP has the /3GB boot option to
>> allow 3 GiB per process. On PCs, free operating systems and server
>> Windows can use PAE to give access to full 4 GB per process.
> No, PAE can be used to access much more memory than 4GB - albeit 
> through paging. AFAIK up to 2^36 Bytes.
PAE is for the kernel. Yes, you can use much more memory with 32 bit 
kernel + PAE. But the ~3G per 32bit process limit still applies. It is 
because the PAE extension allows the kernel to distribute the same 
virtual address ranges between different processes, but map them to 
different physical memory addresses. However, the process that was 
compiled and is running in 32 bit mode, cannot access more than ~3GB 
simply because it is not able to address more memory locations with 32 
bit addresses. (minus ~1G is because it needs virtual addresses for I/O 
devices as well, and those addresses cannot be mapped to physical memory).

So with any Python that is running in 32 bit mode, you cannot use more 
than ~3G memory. But you can start many instances of those programs and 
use 2G for each process.


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