- The Accelerated Graphics Port
Do you see any difference
between these two images? If not, look closely.
Take a look at Image 1.
Focus on the decals, the beacons on the top deck, and the missiles hanging
under the wings in the first image. You can't really see them, can you?
They are all fuzzy. Now, look at the second image. Can you
see that dramatic improvements in the jets' details? The decals are
all readable, the missiles can be deciphered as missiles, and many other
elements can be seen. The overall fuziness has been lifted!!
You may ask,
How was this done?
The simple answer is the
Accelerated Graphics Port
What is the Accelerated
The Accelerated Graphics
Port (AGP) interface is a new platform bus specification that enables high
performance graphics capabilities, especially 3 dimensional, on PCs. It
is a dedicated bus from the graphics subsystem to the core-logic chipset.
This new bus shifts the memory requirements for the 3D portions of a graphics
subsytem from the local frame buffer memory to main system memory
The benefits of AGP include:
Peak Bandwidth 4x the PCI bus,
and higher sustained rates via sideband addressing and pipelining, and
more data transfers per clock
enables graphics cards to execute
texture maps directly from system memory instead of forcing it to pre-load
the texture data to the graphics's cards local memory - Direct Memory Execute
Reduced Contention with the
CPU and I/O devices for bus and memory access. The PCI bus serves disk
controllers, LAN chips, and possibly video capture. AGP operates concurrently
with, and independent from, most transactions on PCI. Further, CPU accesses
to system RAM can proceed concurrently with the graphics chip's AGP RAM
reads, because of so-called out-of-order and queuing hardware support in
the chip set. So in spite of heavy access from the graphics chip, there
should be no audio breakup or other CPU degradation.
An "extra port" to the graphics
chip for memory access, so it can concurrently read textures from AGP memory
while reading/writing Z-values and pixels from local memory. Allowing
the CPU to write directly to shared system AGP memory when it needs to
provide graphics data, such as commands or animated textures. Generally
the CPU can more quickly access main memory than it can graphics local
memory via AGP, and certainly faster than via the PCI bus.
Enables new classes of applications
on the PC such as 3D CAD/CAM, data visualization and 3D user interfaces
1998, Hank Kuo and Adam Labelson.