This is the processor used in the iPod touch 3G.
Geohot has made use of his previously undisclosed bootrom exploit in limera1n. It is also implemented in Chronic Dev's greenpois0n. Source code for Greenpois0n can be found here: https://github.com/Chronic-Dev/syringe
The load address is at 0x41000000 (same as the S5L8920).
The entire boot chain (except the bootrom) resides on the NAND flash (instead of part of it on NOR flash as in earlier devices). This is the only main difference from the S5L8920 used in the iPhone 3GS.