What is the "graphics memory base aperture" in Intel chipsets?

Question

I am trying to understand how I can draw simple graphics in x86 protected mode on Intel chipsets. I already (sort of) know how to do this with the VGA interface, and I'm trying to figure out how to use the G35 Express for this. For this, I am studying this document .

I cannot understand what the "aperture base of graphic memory" is; Is there anything in the PCI configuration space with this name? For example, on page 164 the document says:

It represents the offset from the database aperture graphics and is displayed on physical pages through the global GTT.

I still need to learn a lot, I only looked through previous volumes, but I suspect that this is an important concept. Also, do you know where I can find a friendly explanation of this architecture or another Intel?

EDIT - some additional findings

I am looking at another Intel document, 317607.pdf, and it looks like they call the “Graphics memory range address” on page 231 actually “The basic graphics memory aperture register” on page 58. However, this is a PCI configuration register starting with 0x18.

@SPRQ: Thank you, I think this looks like an AGP aperture, but as per page 52 of the same document:

Note. AGP Aperture no longer exists with PCI Express.

This is something else.

Answer 1

“Aperture memory database” is a reference to AGP memory or system memory displayed for use by the graphics controller for image buffers or instructions. GTT is a translation table table similar to CPU MMU page tables for mapping the physical memory of a system into the AGP linear address space. Thus, in the AGP memory space, you can deal with a logically continuous address space, which is displayed by the chipset and the graphics controller on a set of links to physical memory addresses from the CPU.

Answer 2

good link http://msdn.microsoft.com/en-us/library/windows/hardware/ff568296(v=vs.85).aspx . This explains why the diaphragm space is used.