Intel 820E manual Combination Host-Side/Device-Side IDE Cable Detection

Intel® 820E Chipset

R

Figure 46. Combination Host-Side/Device-Side IDE Cable Detection

		IDE drive	IDE drive
		5 V	5 V
	To secondary
			10 kΩ
IDE connector		10 kΩ
GPIO		40-conductor
		cable
ICH2			PDIAG#
	PDIAG#/	PDIAG#
GPIO	CBLID#
	10 kΩ
Resistor required for		IDE drive	IDE drive
non-5V-tolerant GPI.			5 V
		5 V
	To secondary
	IDE connector	10 kΩ	10 kΩ
GPIO		80-conductor
		IDE cable
ICH2	PDIAG#/	PDIAG#	PDIAG#
GPIO	CBLID#
	10 kΩ
		Open
Resistor required for
non-5V-tolerant GPI.			IDE_combo_cable_det

After diagnostics, this mechanism allows the BIOS to sample PDIAG#/CBLID#. If the signal is high, there is a 40-conductor cable in the system and ATA modes 3, 4 and 5 must not be enabled.

If PDIAG#/CBLID# is detected low, then there may be an 80-conductor cable in the system, or there may be a 40-conductor cable and a legacy slave device (Device 1) that does not release the PDIAG#/CBLID# signal as required by the ATA/ATAPI-4 standard. In this case, BIOS should check the IDENTIFY DEVICE information in a connected device that supports Ultra DMA modes higher than 2. If ID Word 93 bit 13 is 1, then an 80-conductor cable is present. If this bit is 0, then a legacy slave (Device

1)is preventing proper cable detection, and the BIOS should configure the system as though a

40-conductor cable were present and notify the user of the problem.

Design Guide 81