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.

10.5.3Determining a Drive’s Transfer Rate Capabilities10.5.3.1Overview

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

Bits

 

Field

Offset

 

 

 

 

 

 

 

 

 

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

 

 

 

 

 

Intel® 460GX Chipset Software Developer’s Manual

10-3