IFB Usage Considerations

Configurations where a drive reports a PIO speed much slower than its reported DMA speed require the DMA Timing Enable Only Select bit to be Enabled.

Table 10-8. IDE Mode/Drive Feature Settings for Optimal DMA/PIO Operation

 

 

 

 

 

 

 

 

 

 

 

 

 

Slave IDE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Timing

 

 

 

DMA

 

 

IORDY

 

 

 

 

 

 

IDE

Register

IDE

IFB IDE

IFB IDE

 

Pre-Fetch

 

Fast

DMA

 

IORDY

Fast

Value

 

 

Pre-Fetch

Timing

Timing

Timing

 

Sample

Timing

Timing

Sample

Timing

(hex)

Drive 0

Drive 1

 

and Posting

and Posting

Register

Register

Enable

 

Point

 

Bank

Enable

Point

Bank

bits 3:0

Mode

Mode

 

Enable

 

Enable

Value

Value

Only

 

Enable

 

Drive

Only

Enable

Drive

(Primary)

Settings

Settings

a

Select 0

b

Select 1

bits 15:8

bits 7:0

Select 0

Select 0

Select 0

Select 1

Select 1

Select 1

OR

 

 

 

 

 

 

(hex)c

(binary)

 

 

 

 

 

 

 

 

 

 

 

 

 

bits 7:4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Second-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ary)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

All

All

 

 

 

 

 

 

 

 

 

 

 

 

 

speeds

speeds

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 4

Mode 0

Depends

Enabled

Enabled

 

Enabled

Disabled

Enabled

Disabled

Disabled

A3

0

0x00xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

 

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 4

Not

Depends

Enabled

Enabled

 

Enabled

Disabled

Disabled

Disabled

Disabled

A3

0

0000xx11

 

Present

on Drive

 

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 4

Mode 2

Depends

Enabled

Enabled

 

Enabled

Depends

Enabled

Depends

Enabled

E3

4

xxx1xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

on Drive

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 4

Mode 3

Depends

Enabled

Enabled

 

Enabled

Depends

Enabled

Enabled

Enabled

E3

9

xx11xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 4

Mode 4

Depends

Enabled

Enabled

 

Enabled

Depends

Enabled

Enabled

Enabled

E3

B

xx11xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 3

Mode 0

Depends

Enabled

Enabled

 

Enabled

Disabled

Enabled

Disabled

Disabled

A1

0

0x00xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

 

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 3

Not

Depends

Enabled

Enabled

 

Enabled

Disabled

Disabled

Disabled

Disabled

A1

0

0000xx11

 

Present

on Drive

 

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 3

Mode 2

Depends

Enabled

Enabled

 

Enabled

Depends

Enabled

Depends

Enabled

E1

4

xxx1xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

on Drive

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 3

Mode 3

Depends

Enabled

Enabled

 

Enabled

Depends

Enabled

Enabled

Enabled

E1

9

xx11xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 3

Mode 4

Depends

Enabled

Enabled

 

Enabled

Depends

Enabled

Enabled

Enabled

E1

B

xx11xx11

 

 

on Drive

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 2

Mode 0

Depends

Enabled

Depends

Enabled

Disabled

Enabled

Disabled

Disabled

90

0

0x00xxx1

 

 

on Drive

 

(if fixed disk)

on Drive

 

 

 

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 2

Not

Depends

Enabled

Depends

Enabled

Disabled

Disabled

Disabled

Disabled

90

0

0000xxx1

 

Present

on Drive

 

(if fixed disk)

on Drive

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 2

Mode 2

Depends

Enabled

Depends

Enabled

Depends

Enabled

Depends

Enabled

D0

4

xxx1xxx1

 

 

on Drive

 

(if fixed disk)

on Drive

 

 

on Drive

(if fixed disk)

on Drive

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 2

Mode 3

Depends

Enabled

Depends

Enabled

Depends

Enabled

Enabled

Enabled

D0

9

xx11xxx1

 

 

on Drive

 

(if fixed disk)

on Drive

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 2

Mode 4

Depends

Enabled

Depends

Enabled

Depends

Enabled

Enabled

Enabled

D0

B

xx11xxx1

 

 

on Drive

 

(if fixed disk)

on Drive

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 0

Mode 0

Disabled

 

Enabled

Disabled

 

Disabled

Disabled

Enabled

Disabled

Disabled

80

0

0000000

 

 

 

 

(if fixed disk)

 

 

 

 

(if fixed disk)

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 0

Not

Disabled

 

Enabled

Disabled

 

Disabled

Disabled

Disabled

Disabled

Disabled

80

0

0000000

 

Present

 

 

(if fixed disk)

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 0

Mode 2

Disabled

 

Enabled

Disabled

 

Disabled

Depends

Enabled

Depends

Enabled

C0

4

xxx10000

 

 

 

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

on Drive

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 0

Mode 3

Disabled

 

Enabled

Disabled

 

Disabled

Depends

Enabled

Enabled

Enabled

C0

9

xx110000

 

 

 

 

(if fixed disk)

 

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode 0

Mode 4

Disabled

 

Enabled

Disabled

 

Disabled

Depends

Enabled

Enabled

Enabled

C0

B

xx110000

 

 

 

 

(if ifxed disk)

 

 

 

on Drive

(if fixed disk)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

cba.

NOTES:

1.DMA Timing Enable Only field is in general Disabled. It is only Enabled in certain cases if the DMA Mode capability of the drive is much greater than the PIO Mode capability of the drive.

2.The IORDY Sample Point field must be Enabled for PIO Modes 3 and 4. It is Enabled on PIO2 drives if and only if IORDY capability is supported in the drive.

3.The above recommendations assume that if the attached slave drive is Mode 0 or not present, SITRE bit is ’0’.

10-10

Intel® 460GX Chipset Software Developer’s Manual