Mac G5 here. Dual 2GHz, 1 GB RAM. Safari, BBEdit, TextEdit, Mail running in the background. I ran the test a couple of times and seemed to get different speeds each time. One was 5 min 7 seconds, another 4 min 35 seconds. Then I increased the bucket size to 128, which is what I normally use, and then the render took just under 3 minutes. Decreased bucket to 32 again and got another 4 min 35 seconds.