What happens when PVRs change?
For some PowerPC processors, the wrong PVR value can be read via the scan chain shadow-PVR register if the scan chain is read without first applying a valid HRESET#. The correct PVR value can still be read using assembly code. A value is loaded into the PVR shadow register in the scan chain at power-up. On some processors, this value may differ from the correct PVR for the part. The HRESET# process loads the correct value into the shadow PVR. After HRESET#, the correct value can be read from the shadow PVR via the scan chain. Since PowerPC assembly code reads the actual PVR instead of the shadow PVR, code will always read the correct value.
