Antivirus

[David75]

I'm sure Avast will scan much faster if you unticked "Scan Archives", and further still if you chose the default "Medium" sensitivity rather than a "Thorough" scan. But yes, it is one of the slower antivirus products I've seen.

I'm just wondering what the bottleneck is, since it's definitely not CPU.

My guess is that some antivirus programs organise the scan so that it is more like a sequential read, rather than a random one. There's a lot of time to gain from that, even more on small files.