I know you said you don't want external plugins but skidder works very nicely for the gate part of the sound... and it's free:
Destroy FX : Audio Units
Just get a pad where the filter is modulated to emulate that sound. There should be a few in ES2 that fit the bill.
If you want to do the gating a different way, set up a kick drum and program the patterns you want. Set that kick track to have no output. Then put a gate on your pad sound. Set the sidechain key of that gate to be the kick drum track. Bam, you have a rhythmic gating.
(EDIT, you'll also want some delay to get closer to that original sound)