[Ubuntu-BR] Linux + 4GB Ram
aleximandro em gmail.com
Terça Junho 24 17:46:30 UTC 2008
> então o que eu estou falando que um processador de 32 bits consegue no
> maximo acessar 4GB de memória.
> quanto é 4.294.967.296 ????
Consegu usar, mas não fica disponível todos os 4 GB para usar alocar no SO
Uma fonte interessante:
"Given the method with which PCI addresses memory beyond 32 bits, there is a
failure mode that is subtle. Any I/O range that "spans" across two 4-GB
regions must be treated specially. If not, the address range will be
correctly decoded for only one part of the transfer and the remaining part
will be transposed to an incorrect memory location. This will corrupt memory
and will crash the system, crash the application, or silently corrupt data
at that location. Applications cannot prevent this because they are only
presented virtual addresses and have no visibility to the physical level.
All operating systems that use PAE face this problem, but some do not
explicitly prevent this from occurring and instead depend on the device
driver to take the correct actions."
"As the physical memory increases, the relative amount of I/O addresses
beyond 32 bits also increases in relation to those addresses below 32 bits.
In most cases, the operating system transparently provides double buffering,
although some Unix variants do not provide any assistance in this function
and require any 32-bit devices and drivers to manage their own double
buffering routines and allocations."
Com "PAE" ativo seriam então 36 bits... ou seja tem a limitação da
plataforma 32bits como um todo, no máximo tu vai conseguir 3,72 GB
kernel/user space (creio eu).
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