Entering a market for PDAs (personal digital assistants) that has been primarily a three-horse race between Palm Inc., Microsoft Corp., and Research in Motion (RIM), S3 Inc. on Tuesday announced its Diamond Mako handheld.

The seven-ounce Diamond Mako with a clamshell design will use London-based Psion Computers Epoch 32 operating system and feature 16MB of memory plus Microsoft- or Lotus-compatible word processing and spreadsheet applications.

Like its competitors, S3, based in Santa Clara, Calif., will offer the unit with a cradle for synchronizing applications with the desktop, as well as an infrared port and the usual personal information management applications: calendar, to-do, tasks, and contacts. The unit will also offer the largest keyboard of its three competitors.

Wireless connectivity will be accessed via an optional 56Kbps infrared modem or an infrared-enabled GSM (Global System for Mobile communications) phone using a GSM wireless service provider. The wireless technology supplied with the unit will also enable users to access e-mail and browse the Web.

The units will be offered through such U.S. stores as Best Buy, Circuit City, and CompUSA by the end of the month and will have a manufacturer’s suggested retail price of US$399.