To add to what Sergejs said... the task manager in windows CPU is measured every couple seconds (you can adjust the update speed in the menu).
In the dude it reads the oid every 30 seconds(if you are using the default). So the graph will be similar but not exactly the same as task manager... The cpu could spike for 20 seconds between each each read and you would not notice the spike.
You really do not want the dude trying to poll anything every few seconds unless you are just doing some testing.
Also some devices (Cisco) contain multiple CPU counters. The 3 OIDs in a Cisco are for 5 minute 1 minute and 5 second average CPU.
If you are collecting every 30 seconds on a the 5 minute average OID you will not get a very accurate picture of the CPU.
It depends what you are trying to know over time... You can find some surprising stuff out. Like this Cisco box has some problem where the CPU climbs very slowly. You can see where it failed over to the 2nd supervisor back in March and it is climbing again...
ciscocpu.png
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