The company is billing the Deskstar 7K400 as the largest-capacity ATA drive with 3.5-inch platters. Currently, the largest 3.5-inch ATA drive is a 320GB product from Maxtor, according to John Monroe, an analyst at research firm Gartner. That drive, though, spins at 5,400rpm, which translates into slower performance than a 7,200rpm drive, Monroe said. He said 3.5-inch ATA drives running at 7,200rpm top out at 250GB.