windows 7使用ram 最大還是3.2g?

Cudacke Dees

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Cudacke Dees

個人積分：89分

文章編號：16409800

syntech wrote:
但是這剩下的5%到底該改用x64 還是 server OS?
如果你是這5%的人,你該怎麼辦.
你有沒有其他的選擇,
因為有時候就是這麼倒楣,你非在 X86 個人OS上作這種需要大量記憶體的工作.

偶就這 5% 的人啊,
64bit 系統偶都用了至少兩年了........

freaky_jon

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freaky_jon

個人積分：98分

文章編號：16449466

陳奭芥 wrote:
這是篇難得又熱心的好...(恕刪)

這沒有什麼穩定性的問題，只是虛擬記憶體轉譯成實體記憶體的方式不一樣。

***32-bit Windows***
32-bit virtual address:
2-level translation
0 bit for page directory (1 page directory)
10 bits for page directory entries (PDEs) (1024 page tables)
10 bits for page table entries (PTEs) (every page table has 1024 pages)
12 bits for page byte offset (every page size is 4K bytes)

***32-bit Windows with PAE***
32-bit virtual address:
3-level translation
2 bits for page directories (4 page directories)
9 bits for page directory entries (PDEs) (512 page tables)
9 bits for page table entries (PTEs) (every page table has 512 pages)
12 bits for page byte offset (every page size is 4K bytes)

Cudacke Dees

89分

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Cudacke Dees

個人積分：89分

文章編號：16449895

freaky_jon wrote:
這沒有什麼穩定性的問...(恕刪)

就是因為如此才有穩定性的問題.

"Enabling "PAE" means that an extra level of page tables gets used. This leads to the following changes:

- One extra level is added to the page table lookup. This can possibly make memory address slower, but usually the difference is not noticeable since the lookup is cached in TLBs.

- Data Execution Protection (DEP) is possible. Adding the extra level of page tables frees up a few bits in the page table descriptor. One of these newly freed bits is now used to mark a page as not-executable.

- Access to up to 16 GB of physical memory is possible.

- Some kernel pointers are now 64 bits.

So if you enable PAE, and your motherboard actually connects at least 33 address pins from the CPU to the memory, and your BIOS supports memory remapping, you should be able to get a full 4 GB of RAM, right?

Nope. Not if you have XP SP2 or Vista, anyway.

Notice that part about kernel pointers being 64 bits. A whole bunch of drivers don't handle that correctly. So as of XP SP2 (also in Vista), even in PAE mode, pointers are limited to 32 bits. Even though the OS and the hardware is fully capable of working with more memory, the OS never touches anything above the 4GB boundary. This was a conscious decision. Stability of the system was considered more important than access to the extra physical memory."
(http://www.codinghorror.com/blog/archives/000811.html)

http://www.codinghorror.com/blog/archives/000811.html