ACPI GAS System Memory

[rizor]

Hi,

I found an entry in the ACPI tables.
The GAS can contain System Memory informations.
Does it mean, that I can detect the physical memory with ACPI and the GAS-entries?
I could not find something helpful about the System Memory entry.
Does someone have experiences with this type of memory detection?

Thanks.

rizor

[Brendan]

Hi,

I found an entry in the ACPI tables.
The GAS can contain System Memory informations.
Does it mean, that I can detect the physical memory with ACPI and the GAS-entries?
I could not find something helpful about the System Memory entry.
Does someone have experiences with this type of memory detection?

Imagine if I wanted to tell you where I stored something. I could tell you the physical address of it (e.g. with a pointer), but that wouldn't work if it was stored at an IO port or in PCI configuration space. I could tell you which address space (e.g. physical address space, or IO port space, or PCI configuration space, or...) and which address within that address space; but then you still wouldn't know if whatever I stored was 8-bit or 16-bit or 32-bit or 64-bit. I'd have to tell you all three things - which address space, which address in that address space, and what size. If I stored lots of completely different things all over the place, then to make it easier I could create a structure that contained all 3 pieces of information. That is all the GAS (or "Generic Address Structure") is - you can think of it as a complicated pointer.

It has nothing to do with memory detection at all.

To detect memory correctly (as per the ACPI specs), see "Chapter 14, System Address Map Interfaces". This chapter describes the different interfaces that are used on different systems. For 80x86 "PC BIOS" systems, you want "Section 14.1, INT 15H, E820H - Query System Address Map".


Cheers,

Brendan

[rizor]

Okay, thank you.
I understood it wrong.
I thought that ACPI has all memory maps, but I have to check myself.

Thank you