How are reserved and ACPI NVS memory sizes counted?

2

My PC has 8GB of memory installed and is running Win 7 64-bit. I ran a tool named fwmemmap that shows the firmware memory map for the system but it's showing around 60MB more than is physically installed -

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The total of all type 1 (memory) adds up to 8142MB which is correct and is also correlated in Windows -

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I would have expected the total of the type 2 (reserved) and type 4 (ACPI NVS) memory to equal 50 MB to bring the total to 8192 MB but it equals around 110MB? Which is more than is physically installed.

Is anyone able to explain why this is?

Any help would be appreciated,

Thanks.

RJSmith92

Posted 2014-04-07T21:26:42.603

Reputation: 820

1It reads like those are reserved address ranges, not memory. – Der Hochstapler – 2014-04-07T21:52:25.020

@OliverSalzburg Thanks for the comment. Is the total reserved address higher than the physical memory installed becuase addresses for I/O devices are being counted? – RJSmith92 – 2014-04-08T11:47:48.470

To make sense of the output, we would need to know what this tool actually is and what it's supposed to do. So far you've simply presented a list of addresses and an assumption you've made based on observing them. – Der Hochstapler – 2014-04-08T12:05:13.070

The tool is called fwmemmap and shows the memory map that is created by the firmware. – RJSmith92 – 2014-04-08T12:07:18.707

Answers

0

From my understanding, the output of fwmemmap applies to a more general understanding of memory than physical memory.

Only some of those address ranges actually map to physical memory, as pointed out on the website:

Ranges that are addressable as RAM are marked “memory”. To interpret other values in the Type column, refer to the definition of int 15h function E820h in the Advanced Configuration and Power Interface (ACPI) Specification, Section 14, System Address Map Interfaces. Note that the map has holes: int 15h function E820h does not report “standard PC address ranges” or areas of address space that are used “for the memory mapping of PCI devices, ISA Option ROMs, and ISA Plug and Play cards”.

Der Hochstapler

Posted 2014-04-07T21:26:42.603

Reputation: 77 228

Asked: 2014-04-07T21:26:42.603

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Active: 2014-04-08T12:21:59.097