IFB Usage Considerations

Table 10-9. DMA/PIO Timing Values Based on PIIX Cable Mode/System Speed

 

 

 

IDETIMx

IDETIMx

SIDETIM

 

 

 

 

Value

 

 

 

 

Value

 

 

IORDY

 

Value

Drive 0

 

 

Recovery

Drive 1

Resultant Cycle

IFB Drive

Drive 0

(Master) if

Sample

(Slave)

Time (Total

Time (RCT)

(Master)

no Slave

Mode

Point (ISP)

bits 3:0

Clocks Base

bits 1:0

if Slave

Attached or

 

bits 1:0

(Primary) or

Operating Freq)

 

 

Attached

Slave is

 

 

 

bits 7:4

 

 

 

 

bits 15:8

Mode 0

 

 

 

 

(Secondary)

 

 

 

 

 

bits 15:8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PIO0/

Default

Default

C0h

80h

0

30 MHz: 900ns

Compatible

 

 

 

 

 

33 MHz: 900ns

 

 

 

 

 

 

 

PIO2/SW2

4 clocks

4 clocks

D0h

90h

4

30 MHz: 256ns

 

 

 

 

 

 

33 MHz: 240ns

 

 

 

 

 

 

 

PIO3/MW1

3 clocks

3 clocks

E1h

A1h

9

30 MHz: 198ns

 

 

 

 

 

 

33 MHz: 180ns

 

 

 

 

 

 

 

PIO4/MW2

3 clocks

1 clock

E3h

A3h

B

30 MHz: 132ns

 

 

 

 

 

 

33 MHz: 120ns

 

 

 

 

 

 

 

10.5.6.2Ultra DMA Timing Settings

The following settings apply to Ultra DMA Mode Settings only.

Table 10-10. Ultra DMA Timing Value Based on Drive Mode

 

 

SDMAC Value

SDMATIMx Value

 

DMA Speed Used on

Ultra DMA Mode Enable x:

Ultra DMA Cycle Time x:

 

Drive 0: bit 0

Drive 0: bits 1:0

IFB Drive Mode

DMA Based Data

Drive 1: bit 1

Drive 1: bits 5:4

 

Transfer Commands

 

Drive 2: bit 2

Drive 2: bits 9:8

 

 

 

 

Drive 3: bit 3

Drive 3: bits 13:12

 

 

 

 

N/A (Ultra DMA Not

Non-ultra DMA

Disabled

Default

Supported)

if supported

 

 

 

 

 

 

Ultra DMA Mode 0

Ultra DMA Mode 0

Enabled

00b: CT=4 clks, RP=6 clks

 

 

 

 

Ultra DMA Mode 1

Ultra DMA Mode 1

Enabled

01b: CT=3 clks, RP=5 clks

 

 

 

 

Ultra DMA Mode 2

Ultra DMA Mode 2

Enabled

10b: CT=2 clks, RP=4 clks

 

 

 

 

10.5.7Drive Configuration for Selected Timings

Once the IFB Timing Modes for DMA, PIO and Ultra DMA have been selected, the Set Features Command (0 x EF) with Set Transfer Mode (subcommand 0 x 03) can be issued to set the drives on the system to the optimal speeds:

Intel® 460GX Chipset Software Developer’s Manual

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