Specifications

Computer Architecture and Maintenance (G-Scheme-2014)
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.
Q. What is the difference between an AGP and a PCI graphics card?
Answer: The biggest difference between AGP and PCI graphics cards is that AGP cards
can access the system memory to help with complex operations such as texture
mapping. PCI cards can only access the memory available on the actual card. AGP
doesn't share bandwidth with other devices, whereas PCI cards do. AGP also makes
pipelined requests, which means it can execute multiple instructions at one time. PCI
cards are not pipelined, which means each instruction has to finish before the next one
is run.
So, with all these great advantages of AGP, you'd think it would be the clear
winner in performance, right? Well, not quite. Tests of similar AGP and PCI graphics
cards show they perform almost the same (typically measured in frames per second).
The area where AGP really shines is in high-resolution tests, where the direct access to
the system memory is most beneficial.
If you're installing an AGP or PCI card in your computer, the AGP slot is usually
the shortest and should be brown. The PCI slots are slightly longer and are colored
white. The actual size of the cards can vary as much as a few inches, though the pins on
the bottom of the card should match the correct slot.
Important: AGP and PCI slots are different sizes. Therefore, AGP cards can only be
placed in AGP slots and PCI cards will only fit in PCI slots.
Q.Compare AGP and PCI
Ans. AGP will deliver a peak bandwidth that is 4 times higher than the PCI bus using
pipelining, sideband addressing, and more data transfers per clock.
It will also enable graphic cards to execute texture maps directly from system memory
instead of forcing it to pre-load the texture data to the graphics card's local memory.
Features that set AGP apart from PCI
• Probably the most important feature of AGP is DIME (direct memory execute).
This gives AGP chips the capability to access main memory directly for the
complex operations of texture mapping.
• AGP provides the graphics card with two methods of directly accessing texture
maps in system memory: pipelining and sideband addressing.
• AGP makes multiple requests for data during a bus or memory access, while PCI
makes one request, and does not make another until the data it requested has
been transferred.
Prepared By – Prof. Manoj.kavedia (9860174297 – 9324258878 ) (www.kavediasir.yolasite.com)
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