Determining A Drive's Best Ultra Dma Capability; Determining A Drive's Best Multi Word Dma/Single Word Dma (Non-Ultra Dma) Capability; Identify Device Information Used For Determining Ultra Dma Drive Capabilities - Intel 460GX Software Developer’s Manual

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.
Table 10-2. Identify Device Information Used for Determining Ultra DMA Drive Capabilities
Capability
Ultra DMA
Ultra DMA
Ultra DMA
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.
Intel® 460GX Chipset Software Developer's Manual
Word
Bits
Offset
53 2 Field Validity
0: the fields reported in word 88 are not valid
1: the fields reported in word 88 are valid
88 10:8 Ultra DMA Modes Active*
bit 10: 1: Ultra DMA Mode 2 is active
bit 9: 1: Ultra DMA Mode 1 is active
bit 8: 1: Ultra DMA Mode 0 is active
88 2:0 Ultra DMA Modes Supported*
bit 2: 1: Ultra DMA Mode 2 is supported
bit 1: 1: Ultra DMA Mode 1 is supported
bit 0: 1: Ultra DMA Mode 0 is supported
IFB Usage Considerations
Field
0: Ultra DMA Mode 2 is not active
0: Ultra DMA Mode 1 is not active
0: Ultra DMA Mode 0 is not active
0: Ultra DMA Mode 2 is not supported
0: Ultra DMA Mode 1 is not supported
0: Ultra DMA Mode 0 is not supported
10-5