28 Oct
2010
28 Oct
'10
1:36 p.m.
In article <4CC979A0.22930.152134D at cclist.sydex.com>,
"Chuck Guzis" <cclist at sydex.com> writes:
You asked if it was used on modern PCs. The answer is yes. Every PC
these days supports standard VGA/monochrome display adapter
functionality which uses a memory-mapped framebuffer. Even the
high-end 3D cards support this functionality, albeit as a legacy from
past architectures.
Some modern video cards use memory-mapped IO for their interaction with
the CPU in terms of doing things like providing a common address space
for uploading textures and other 3D data. They don't provide
low-level control registers to the CPU for manipulating the video card
because that eliminates potential parallelism between the CPU and the
GPU. The GPU has become a smart coprocessor with shared address space
for transferring large amounts of data that needs to be directly
manipulated by the CPU and the GPU.
--
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
<http://legalizeadulthood.wordpress.com/the-direct3d-graphics-pipeline/>
Legalize Adulthood! <http://legalizeadulthood.wordpress.com>
Memory mapped
IO is ubuiqitous in MS-DOS based PCs, as it is generally
fastest to write directly to the memory-mapped display memory for
CGA > and VGA displays.
And there were other PC displays, that didn't use memory-mapped video
at all.