April 11 (Reuters) - Marvell Technology on Thursday said it has won new business helping large U.S.-based cloud computing firms make custom chips for artificial intelligence but that its custom unit carries lower margins than other lines of business.

Shares fell 2.7% after Marvell executives discussed the business during an investor presentation. Marvell helps customers such as Amazon.com design custom chips for their cloud units and competes against rivals such as Alphabet Inc supplier Broadcomm in that business. (Reporting by Stephen Nellis in San Francisco and Arsheeya Singh in Bengaluru)