Quartus® II 10GBASE-R PHY MegaCore does not allow a user to pick some of the pre-emphasis, Vod or DC gain values from the full range of legal values, due to a software bug. Setting some of the legal values in MegaCore are incorrectly flagged as out of range values.
To workaround the problem, you can generate the MegaCore using any of the allowed values. You can then open up the top level MegaCore generated file in a text editor and manually change those values.
For example, on the "Analog Options" tab of 10GBASE-R PHY MegaCore for Stratix IV GX/GT devices, if you add a pre-emphasis first post-tap setting of 16, it is flagged by the MegaCore as out of range value. To work around the problem, generate the MegaCore using default values. Open up the top level MegaCore generated file and change the first post-tap value to 16, at following two locations.
// Retrieval info: <generic name="tx_preemp_tap_1" value="16" />
You'll need to make sure that you are using one of the allowable values described in the device handbook. This issue is seen in Quartus II 10.0, 10.0sp1, 10.1, 10.1sp1 and 11.0 software. It will be fixed in future software versions.