Table schema:
CREATE TABLE table_name_56 (part_number_s_ VARCHAR, l2_cache VARCHAR, frequency VARCHAR)

Question: What's the part number of the processor that has an 1.8 ghz frequency and 2 × 256 kb L@ Cache?
SQL: SELECT part_number_s_ FROM table_name_56 WHERE l2_cache = "2 × 256 kb" AND frequency = "1.8 ghz"