The features_string of VM_Version is supposed to be "sifive,u74-mc,rv64imafdc" for the unmatched board, which is made up of "uarch" and "isa" in /proc/cpuinfo.
In contrast, it's "family 6 model 79 stepping 1 microcode 0xb000036, cx8, cmov, fxsr, ht, mmx, 3dnowpref, sse, sse2, sse3, ssse3, sse4.1, sse4.2, popcnt, lzcnt, tsc, tscinvbit, avx, avx2, aes, erms, clmul, bmi1, bmi2, rtm, adx, fma, vzeroupper, clflush" in a x86 platform, and "0x41:0x0:0xd08:2, fp, simd, evtstrm, aes, pmull, sha1, sha256, crc" in aarch64.