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Intel® 460GX Chipset Software Developer’s Manual 10-5
IFB Usage Considerations
10.5.4 Determining a Drive’s Best Ultra DMA Capability
The drive’s ultra DMA mode capability and current configuration are specified in the
IDENTIFY_DRIVE buffer, Word 88. Software must first check to see that the Word 88 is valid
before determining the Ultra DMA drive capability.
The following Ultra DMA drive capabilities are supported by the IFB, from fastest to slowest:
• Ultra DMA Mode 2
• Ultra DMA Mode 1
• Ultra DMA Mode 0
• Disabled (Drive does not support any of the above Ultra DMA Modes.)
10.5.5 Determining a Drive’s Best Multi Word DMA/Single Word
DMA (Non-ultra DMA) Capability
This section describes how to determine a drive’s multi word DMA and single word DMA
capabilities.
The following DMA drive capabilities are supported by the IFB, from fastest to slowest:
• Multi Word DMA Mode 2
• Multi Word DMA Mode 1
• Single Word DMA Mode 2
• Disabled (Drive does not support any of the above Multi/Single DMA Modes.)
Software at this stage needs to determine if at least one of the above modes is supported by the
drive. Software should initially determine a drive’s best Mult Word DMA capability initially. If a
drive doesn’t support multi word DMA Modes 0 or 1, then software should check if single word
DMA Mode 2 is supported.
Table 10-2. Identify Device Information Used for Determining Ultra DMA Drive Capabilities
Capability
Word
Offset
Bits Field
Ultra DMA 53 2 Field Validity
0: the fields reported in word 88 are not valid
1: the fields reported in word 88 are valid
Ultra DMA 88 10:8 Ultra DMA Modes Active*
bit 10: 1: Ultra DMA Mode 2 is active
0: Ultra DMA Mode 2 is not active
bit 9: 1: Ultra DMA Mode 1 is active
0: Ultra DMA Mode 1 is not active
bit 8: 1: Ultra DMA Mode 0 is active
0: Ultra DMA Mode 0 is not active
Ultra DMA 88 2:0 Ultra DMA Modes Supported*
bit 2: 1: Ultra DMA Mode 2 is supported
0: Ultra DMA Mode 2 is not supported
bit 1: 1: Ultra DMA Mode 1 is supported
0: Ultra DMA Mode 1 is not supported
bit 0: 1: Ultra DMA Mode 0 is supported
0: Ultra DMA Mode 0 is not supported