http://ttevhjjsjxz6uqqcjkbig5cycd7n7xv7cmd6f5fcvrqaaa7f3bj36wad.onion/technology/security/pow/index.html
This is a drawback in the PoW protection, but we expect that most DoS attacks
won't happen anymore for PoW-enabled Onion Services, or that won't last for
long periods. So under normal conditions -- i.e, without DoS attacks happening
-- slower devices will still be able to connect to PoW-enabled Onion Services
without problems.