Given the advice from agent_smith–

sudo port install htop
Password:
--->  Computing dependencies for htop
--->  Fetching htop
--->  Verifying checksum(s) for htop
--->  Extracting htop
--->  Configuring htop
--->  Building htop
--->  Staging htop into destroot
--->  Installing htop @0.8.3_1
--->  Activating htop @0.8.3_1
--->  Cleaning htop
[download]

And running the sample from BrowserUk, I see this, on my ageing MacBook, with htop–

  1  [||||||||||||||||||||||||||||||||||||||100.0%]     Tasks: 139 tot
+al, 3 running
  2  [||||||||||||||||||||||||||||||||||||||100.0%]     Load average: 
+2.68 1.35 0.96 
  Mem[|||||||||||||||||||||||||||||||||3802/4096MB]     Uptime: 19 day
+s, 20:59:05
[download]

Nice!