From Step 15 (http://www.ifixit.com/Teardown/iPad-Teardown/2183/2):

Markings on the A4:

- N26CGM0T 1007 APL0398 33950084 YNL184A2 1004 K4X2G643GE

- Yes, the K4X2 is a Samsung DRAM part number!

- Decoding the part number shows there is 2Gb of memory inside. This translates into ~256MB of memory.

- This means the A4 processor is probably being manufactured by Samsung.

- The DRAM was stamped at the end of January, while the processor die was likely manufactured the third week of February.