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#31
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Getting Compaq to Boot With 4 Gig Memory
On 17-03-2010 19:04, John John - MVP wrote:
PAE is now a rather old story I have to wonder if Microsoft ever designed PAE to access more than 64GB of RAM. There isn't really much to change. The PTE has always been 64 bit wide. It is just a question of how many of the bits a specific CPU allows to use for addressing memory. |
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#32
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Getting Compaq to Boot With 4 Gig Memory
On 17-03-2010 19:10, dennis wrote:
I'm not sure if the processor makes all the processor width available while in legacy mode? A quote from Intels developer manual (volume 3A): "3.8.1 Enhanced Legacy PAE Paging On Intel 64 processors ... can address physical memory greater than 64-GByte if the implementation’s physical address size is greater than 36 bits." The same goes for AMD. |
#33
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Getting Compaq to Boot With 4 Gig Memory
On 17-03-2010 19:10, dennis wrote:
I'm not sure if the processor makes all the processor width available while in legacy mode? A quote from Intels developer manual (volume 3A): "3.8.1 Enhanced Legacy PAE Paging On Intel 64 processors ... can address physical memory greater than 64-GByte if the implementation’s physical address size is greater than 36 bits." The same goes for AMD. |
#34
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Getting Compaq to Boot With 4 Gig Memory
dennis wrote:
On 17-03-2010 19:10, dennis wrote: I'm not sure if the processor makes all the processor width available while in legacy mode? A quote from Intels developer manual (volume 3A): "3.8.1 Enhanced Legacy PAE Paging On Intel 64 processors ... can address physical memory greater than 64-GByte if the implementation’s physical address size is greater than 36 bits." The same goes for AMD. You're right, on 64-bit processors PAE is wider than 36-bits (I read 40-bits on most processors). And according to Raymond Chen, the memory manager uses 37-bits, hence 128GB maximum. So NUMA has nothing to do with it. I wonder why Microsoft reduced this back to 64GB on Server 2008... John |
#35
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Getting Compaq to Boot With 4 Gig Memory
dennis wrote:
On 17-03-2010 19:10, dennis wrote: I'm not sure if the processor makes all the processor width available while in legacy mode? A quote from Intels developer manual (volume 3A): "3.8.1 Enhanced Legacy PAE Paging On Intel 64 processors ... can address physical memory greater than 64-GByte if the implementation’s physical address size is greater than 36 bits." The same goes for AMD. You're right, on 64-bit processors PAE is wider than 36-bits (I read 40-bits on most processors). And according to Raymond Chen, the memory manager uses 37-bits, hence 128GB maximum. So NUMA has nothing to do with it. I wonder why Microsoft reduced this back to 64GB on Server 2008... John |
#36
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Getting Compaq to Boot With 4 Gig Memory
dennis wrote:
On 17-03-2010 19:10, dennis wrote: I'm not sure if the processor makes all the processor width available while in legacy mode? A quote from Intels developer manual (volume 3A): "3.8.1 Enhanced Legacy PAE Paging On Intel 64 processors ... can address physical memory greater than 64-GByte if the implementation’s physical address size is greater than 36 bits." The same goes for AMD. According to Mark Russinovich: "The maximum 32-bit limit of 128GB, supported by Windows Server 2003 Datacenter Edition, comes from the fact that structures the Memory Manager uses to track physical memory would consume too much of the system's virtual address space on larger systems. The Memory Manager keeps track of each page of memory in an array called the PFN database and, for performance, it maps the entire PFN database into virtual memory. Because it represents each page of memory with a 28-byte data structure, the PFN database on a 128GB system requires about 980MB. 32-bit Windows has a 4GB virtual address space defined by hardware that it splits by default between the currently executing user-mode process (e.g. Notepad) and the system. 980MB therefore consumes almost half the available 2GB of system virtual address space, leaving only 1GB for mapping the kernel, device drivers, system cache and other system data structures, making that a reasonable cut off" http://blogs.technet.com/markrussino...1/3092070.aspx John |
#37
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Getting Compaq to Boot With 4 Gig Memory
dennis wrote:
On 17-03-2010 19:10, dennis wrote: I'm not sure if the processor makes all the processor width available while in legacy mode? A quote from Intels developer manual (volume 3A): "3.8.1 Enhanced Legacy PAE Paging On Intel 64 processors ... can address physical memory greater than 64-GByte if the implementation’s physical address size is greater than 36 bits." The same goes for AMD. According to Mark Russinovich: "The maximum 32-bit limit of 128GB, supported by Windows Server 2003 Datacenter Edition, comes from the fact that structures the Memory Manager uses to track physical memory would consume too much of the system's virtual address space on larger systems. The Memory Manager keeps track of each page of memory in an array called the PFN database and, for performance, it maps the entire PFN database into virtual memory. Because it represents each page of memory with a 28-byte data structure, the PFN database on a 128GB system requires about 980MB. 32-bit Windows has a 4GB virtual address space defined by hardware that it splits by default between the currently executing user-mode process (e.g. Notepad) and the system. 980MB therefore consumes almost half the available 2GB of system virtual address space, leaving only 1GB for mapping the kernel, device drivers, system cache and other system data structures, making that a reasonable cut off" http://blogs.technet.com/markrussino...1/3092070.aspx John |
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