Quartus can't start Fitter (can't load library error) - Quartus can't start Fitter (can't load library error) I have a problem with a Quartus Pro installtion: Everytime I try to synthesis a project, the Fitter stage crashes with the following error: Problem Details Error: Internal Error: Sub-system: ATCL, File: /quartus/ccl/atcl/atcl_root.cpp, Line: 987 ------------------------------------- Error found while sourcing: c:/intelfpga_pro/19.2/quartus/common/tcl/internal/init/fdrgn.pkg_info ------------------------------------- ERROR: Can't load library: c:\intelfpga_pro\19.2\quartus\bin64\fitter_fdrgn.dll. The operating system reports the following error: The specified module could not be found. Stack Trace: 0x535d: err_report_internal_error + 0x2d (CCL_ERR) 0xfe33: atcl_initialize_pkg_info + 0x4e3 (ccl_atcl) 0x10dca: atcl_initialize_quartus_interpreter + 0xaa (ccl_atcl) 0xf742: atcl_get_interpreter + 0x42 (ccl_atcl) 0x2ddf6: ACF_MANAGER_STORAGE_REAL::ACF_MANAGER_STORAGE_REAL + 0x606 (db_acf) 0x2501d: ACF_MANAGER::internal_open_create_project + 0x7bd (db_acf) 0x2697d: ACF_MANAGER::open_project + 0x7bd (db_acf) 0xe1954: QHD_ROOT_IMPL::open_acf_if_needed + 0xc4 (comp_qhd) 0xe084e: QHD_ROOT_IMPL::initialize + 0x10e (comp_qhd) 0x17e73: QCU::DETAIL::initialise_qhd + 0xb3 (comp_qcu) 0x18028: QCU::DETAIL::initialise_qhd_and_perform_checks + 0x98 (comp_qcu) 0x1816c: QCU::DETAIL::intialise_qhd_and_run_qexe + 0x6c (comp_qcu) 0x290bc: qcu_run_tcl_option + 0x2ec (comp_qcu) 0x19c58: qexe_run + 0x438 (comp_qexe) 0x1ad8a: qexe_standard_main + 0x26a (comp_qexe) 0x2052: qfit2_main + 0x82 (quartus_fit) 0x14a08: msg_main_thread + 0x18 (CCL_MSG) 0x160ae: msg_thread_wrapper + 0x6e (CCL_MSG) 0x20fb0: mem_thread_wrapper + 0x70 (ccl_mem) 0x13f8d: msg_exe_main + 0x20d (CCL_MSG) 0x2918: __scrt_common_main_seh + 0x11c (quartus_fit) 0x17bd3: BaseThreadInitThunk + 0x13 (KERNEL32) 0x6cee0: RtlUserThreadStart + 0x20 (ntdll) End-trace Executable: quartus Comment: None System Information Platform: windows64 OS name: Windows 10 OS version: 10.0 Quartus Prime Information Address bits: 64 Version: 19.2.0 Build: 57 Edition: Pro Edition The file it can't load is where it should be. What I've tried until now: Reinstalled Quartus (using both direct download and Download Manager) Installed it into another directory Installed it on another drive Excluted the Quartus directory in the anti virus software Deactived the anti virus software ... but nothing helped ... What else could I try to fix this? Thanks Replies: Re: Quartus can't start Fitter (can't load library error) Thank you very much!!! That solved the problem! I had to install both (x64 and x86), because with the x64 alone Modelsim didn't want to start anymore. But now both are working fine. Replies: Re: Quartus can't start Fitter (can't load library error) Hi, Could you try the workaround suggested in this KDB https://www.intel.com/content/altera-www/global/en_us/index/support/support-resources/knowledge-base/tools/2019/internal-error--sub-system--atcl--file---quartus-ccl-atcl-atclro.html Thanks.