Accelerated Graphics Port (Agp) Bus Interface; Agp 4X Bus - HP XM600 - Kayak - 128 MB RAM Technical Reference Manual

2 System Board
Memory Controller Hub (MCH) 82820
MCH Interface
The MCH interface provides bus control signals and address paths for
transfers between the processors on the Host bus (FSB), Direct Rambus
channel and AGP 4x bus.
The MCH allows the processor to access up to 4 GB of memory. It also
provides an 6-deep In-Order Queue supporting up to six outstanding
transaction requests on the host bus.
The MCH can support one or two Pentium III processors, at FSB frequencies
of 100/133 MHz using GTL+ signalling. Refer to
the devices on the Host bus.

Accelerated Graphics Port (AGP) Bus Interface

A controller for the AGP4x (Accelerated Graphics Port) slot is integrated in
the MCH. The AGP Bus interface is compatible with the Accelerated
Graphics Port Specification, Rev 2.0, operating at 133 MHz, and supporting
up to 1 GB/sec data transfer rates. The MCH supports only a synchronous
AGP interface, coupling to the Host bus frequency.

AGP 4x Bus

The AGP bus is a dedicated bus for the graphics subsystem, which meets the
needs of high quality 3D graphics applications. It has a direct link to the
MCH.
The AGP bus is based upon a 133 MHz, 32-bit PCI bus architecture, to which
several signal groups provide AGP-specific control and transfer
mechanisms.
Pipelining is added along with special sideband signals, increasing the
efficiency of the AGP bus. Thus, you come closer to the theoretical
maximum bandwidth. Although the maximum transfer rate is never
exceeded, the overall transfer rate is increased.
AGP specific transactions always use pipelining. This control mechanism
increases the bus efficiency for data transfer. Sideband Addressing (SBA)
may also be used by AGP transaction requests which also increases the bus
efficiency for data transfer. These two mechanisms can combine
independently to pipelining, which leads to the following operating modes:
FRAME- based AGP. Only the PCI protocol is used: 66 MHz, 32-bits, 3.3
•
V, 266 MB/s peak transfer rate.
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