21154 PCI-to-PCI Bridge Specification Update

Intel Confidential21

Errata

corrupted resulting in a mismatch when the transaction is retried causing the transaction to be

retried continuously. The primary master timeout timer times out (2

the data, and reinitiates the transaction on the next cycle. This transaction usually completes as a

normal delayed read transaction.

Since the 21154 is a highly symmetrical device and the CAM circuitry is duplicated on both the

primary and secondary interfaces the issue may occur on either an upstream or downstream

delayed read transactions.

Implication:

Applications using P_VIO and/or S_VIO=3.3V may experience excessive retries due to a

reduction in noise immunity in the CAM section of the chip. When P_VIO and/or S_VIO is set

above ~3.8V the biasing of the input transistor effectively reduces the resulting core ground

undershoot that is coupled through the ESD protection clamp.

This issue has only been reported in a very small number of high performance applications such as

Video cards, Gigabit Ethernet and 100MByte/s Fibre Channel with P_VIO and/or S_VIO set to

3.3V. Other lower performance applications and implementations with P_VIO and S_VIO set to

5V have not reported the issue. This may also manifest as a layout sensitivity issue.

Workaround:

Setting P_VIO and S_VIO to 5V has proven to eliminate these issues on current designs. Many

21154 designs that implemented the errata 4 work around are already biasing the P_VIO and

S_VIO pins to 5V and should not experience the issues.

Note:P_VIO and S_VIO pins set the value of the voltage clamp only and

has no affect on the signaling levels of the bus.

Status:

No Fix

10.

Secondary Address pins are driven incorrectly during reset.

Problem:

During reset S_AD <63:0>, C/BE# and PAR are driven high. The PCI Local Bus Specification

requires that these pins be driven low during reset.

Implication:

In applications where multiple PCI components implemented on the secondary bus may drive the

bus during reset, there is a potential for device contention if the 21154AE/BE is driving high and

the other device/devices are driving low. This contention may cause excessive power dissipation in

the 21154 and could potentially damage the device.

Workaround:

There is no known work around.

Status:

No Fix