I tested it again without stopping it. Big mistake.

AMD XP-M 2500+ Avast Professional

After 20+ minutes the scanner crashed because it ran out of disk space. It used all 20G of free space I had. I had to restart and manualy delete the temp files.
I ran a boot scan and it scanned the zip quickly but did not find the eicar.

Tried a different machine.
AMD 64-M 3000+ Avast Home

Found the eicar in 11 minutes with no other problems. I did not try the boot scan on this machine. (40G of free disk space)