82845G Datasheet, PDF (21/193 Pages) Intel Corporation – Intel 82845G/82845GL/82845GV Graphics and Memory Controller Hub (GMCH)

Signal Description
Signal Description
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This section provides a detailed description of GMCH signals. The signals are arranged in
functional groups according to their associated interface.
The “#” symbol at the end of a signal name indicates that the active, or asserted state occurs when
the signal is at a low voltage level. When “#” is not present after the signal name the signal is
asserted when at the high voltage level.
The following notations are used to describe the signal type:
I
Input pin
O
Output pin
I/O
Bi-Directional Input/Output pin
s/t/s
Sustained Tri-State. This pin is driven to its inactive state prior to tri-stating.
The signal description also includes the type of buffer used for the particular signal:
AGTL+
Open Drain AGTL+ interface signal. The GMCH integrates AGTL+ termination
resistors, and supports Vtt of from 1.15 V to 1.75 V
AGP
AGP interface signals. These signals are compatible with the Accelerated
Graphics Port Interface Specification, Revision 2.0 1.5 V Signaling Environment
DC and AC Specifications. The buffers are not 3.3 V tolerant.
LVTTL Low Voltage TTL 3.3 V compatible signals
SSTL_2 Stub Series Terminated Logic 2.5 V compatible signals.
CMOS CMOS buffers.
Host Interface signals that perform multiple transfers per clock cycle may be marked as either
“4X” (for signals that are “quad-pumped”) or 2X (for signals that are “double-pumped”).
Note that processor address and data bus signals are logically inverted signals. In other words, the
actual values are inverted of what appears on the processor bus. This must be taken into account
and the addresses and data bus signals must be inverted inside the GMCH host bridge. All
processor control signals follow normal convention. A 0 indicates an active level (low voltage) if
the signal is followed by # symbol and a 1 indicates an active level (high voltage) if the signal has
no # suffix.
Intel^® 82845G/82845GL/82845GV GMCH Datasheet
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