Why does the ATX PLL REFCLK switching not work in simulation when using the Stratix V GX Custom or Low Latency PHY in Quartus II Software version 12.0?

Description

Due to a bug in the simulation model, the ATX PLL REFCLK switching does not work when using the Stratix® V GX Custom or Low Latency PHY in Quartus® II Software version 12.0.

Resolution

To work around this issue, you can temporarily select the CMU PLL in the PHY MegaWizard™ to simulate REFCLK switching.

This issue will be fixed in a future version of Quartus.