EXT91 is ok for use with ASSURA32USR2_HF and above but some features such as the usage of a non-existent net "0" as the ground net requires ASSURA41_HF3 and above. As ASSURA32 is quite out-dated, please download the latest version of Assura41. I would also think that it is better to upgrade to IC614. The "What's New" file has some info on compatibility with the various tools. Most pdks are tested with a specific version of Cadence software and request users to use that particular version but this is hard to follow in practical situations because of the rapid release schedules of software upgrades and bug fixes. If your IBM pdk works for IC613, it will most likely work for IC614. You can simply install IC614 and give it a try. ASSURA41 has releases for both IC613 and IC614 I use an IBM PDK and I've been advised to stick with the tools that the kit was tested with. Specifically my PDK was tested with IC613 and MMSIM71, and the fab service said wait until the next kit patch before upgrading to see if the newer tools are supported. 2. Are you sure that IC614 is a must for ASSURA41? I have a PDK from another foundry which says to use IC613, ASSURA41 and EXT82. I just installed the kit and haven't tested all the tools so I'm not sure if there truly is a compatibility issue.