This is a re-post
from another thread - because I thought the info might be interesting to DS2000 owners.
In regards to how the Rigol decimates a larger number of samples to a smaller number of pixels (e.g. 14k sample length to 700 pixels = 20 samples per pixel when the time base is >= 500ns) - the two common methods being 1/N or Peak-to-Peak:
I did some experimentation using an AWG file of three consecutive short pulses with increasingly higher voltages - with the DSO triggering on the second of the three pulses.
It appears (so far) that the Rigol DS2000 does Peak-to-Peak Decimation from sample to display memory in Normal mode, since if it only displayed every 20th point (using 1/N Decimation), you wouldn't see the amplitude of the third pulse when looking at the display at the 100ms/div setting.
The attached images show 100ms/div and 200us/div displays of Normal mode (@ both 14k and 56Mpts sample lengths) and 100ms/div and 200us/div of Peak Detect mode @ 14kpts.
Peak Detect is a completely different mode of acquisition - I've included it just to show that it can affect the contents of sample memory (as shown at 200us/div) - while Peak-to-Peak Decimation in Normal mode does not.