IFB Usage Considerations

10.5.4Determining 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.

Table 10-2. Identify Device Information Used for Determining Ultra DMA Drive Capabilities

Capability

 

Word

Bits

 

Field

 

Offset

 

 

 

 

 

 

 

 

 

 

 

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

 

 

 

 

 

 

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.)

10.5.5Determining 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.

Intel® 460GX Chipset Software Developer’s Manual

10-5