User's Manual

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
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12.3.12. BR11—BLT Source Pitch (Offset) or Monochrome Source
Quadwords
Memory Offset Address: 4002Ch
Default: None
Attributes: RO; DWord accessible
31 14 13 0
Reserved Source Pitch (Offset) or
Monochrome Source Quadwords
Bit Descriptions
31:14 Reserved.
13:0 Source Pitch (Offset) or Monochrome Source Quadwords. When the color source data is located
within the frame buffer or AGP aperture, these signed 14 bits store the memory address offset (pitch)
value by which the source address originally specified in the Source Address Register is incremented
or decremented as each scan line’s worth of source data is read from the frame buffer by the BLT
Engine, so that the source address will point to the next memory address from which the next scan
line’s worth of source data is to be read.
When the source data is provided by IMMEDIATE_BLT instruction, these 14 bits store the number of
bytes to be counted from the beginning of a scan line’s worth of data to where the next scan line’s
worth of data begins.
Note that if the intended source of a BLT operation is within on-screen frame buffer memory, this
offset is normally set to accommodate the fact that each subsequent scan line’s worth of source data
lines up vertically with the source data in the scan line, above. However, if the intended source of a
BLT operation is within off-screen memory, this offset can be set to accommodate a situation in which
the source data exists as a single contiguous block of bytes where in each subsequent scan line’s
worth of source data is stored at a location immediately after the location where the source data for the
last scan line ended.
When monochrome source data is being processed, this field is used for indicating the total number of
Quadwords of data in the source data stream.