```
bitcoind -par=1
```

Excerpt from the `debug.log`:

```
Using 0 threads for script verification
```

Zero? I guess not ;)
#else
    int fd_max = FD_SETSIZE;
#endif
    nMaxConnections = std::max(std::min<int>(nMaxConnections, fd_max - nBind - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS), 0);
    if (nFD < MIN_CORE_FILEDESCRIPTORS)
        return InitError(_("Not enough file descriptors available.").translated);
    nMaxConnections = std::min(nFD - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS, nMaxConnections);
    if (nMaxConnections < nUserMaxConnections)
        InitWarning(strprintf(_("Reducing -maxconnections from %d to %d, because of system limitations.").translated, nUserMaxConnections, nMaxConnections));
    
    if (gArgs.IsArgSet("-debug")) {
        
        const std::vector<std::string> categories = gArgs.GetArgs("-debug");
        if (std::none_of(categories.begin(), categories.end(),
            [](std::string cat){return cat == "0" || cat == "none";})) {
            for (const auto& cat : categories) {
                if (!LogInstance().EnableCategory(cat)) {
                    InitWarning(strprintf(_("Unsupported logging category %s=%s.").translated, "-debug", cat));
                }
            }
        }
    }
    
    for (const std::string& cat : gArgs.GetArgs("-debugexclude")) {
        if (!LogInstance().DisableCategory(cat)) {
            InitWarning(strprintf(_("Unsupported logging category %s=%s.").translated, "-debugexclude", cat));
        }
    }
    
    int ratio = std::min<int>(std::max<int>(gArgs.GetArg("-checkmempool", chainparams.DefaultConsistencyChecks() ? 1 : 0), 0), 1000000);