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Intel® 460GX Chipset Software Developer’s Manual 10-3
IFB Usage Considerations
NOTES:
• The Ultra DMA Enable bit specifies the current Ultra DMA enabled status:
— Disabled by default: This field needs to be enabled in order to take advantage of the IFB
Ultra DMA timings. When this field is disabled, the IFB Ultra DMA Timing Register is
disabled.
• The Ultra DMA Cycle Time Field specifies the current Ultra DMA timing mode.
Note that this field only applies if the corresponding Ultra DMA Enable field is set.
10.5.3 Determining a Drive’s Transfer Rate Capabilities
10.5.3.1 Overview
The following section provides the information that allows a drive’s capabilities to be determined.
The ATA IDENTIFY_DRIVE (0xEC) and ATAPI IDENTIFY_DEVICE(0x1A) can be used to
determine the capability. Each of these commands returns a 256 word buffer with fields that can
allow the drive’s capabilities to be determined.
Refer to the ATA Specification for more information regarding the IDENTIFY_DEVICE
command.
Table 10-1. Identify Device Information Used for Determining Drive Capabilities
Capability
Word
Offset
Bits Field
Device Type Fields that Indicate Device Type
Device Type 0 15 General Configuration:
0: ATA Device
1: ATAPI Device
Ultra DMA Fields that Indicate Ultra DMA Drive Capabilities
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
PIO, DMA 53 1 Field Validity
0: the fields reported in words 64-70 are not valid
1: the fields reported in word 64-70 are valid