T-Mobile USA unveiled its fastest 4G smartphones on Monday, both running dual-core 1.5 GHz processors and going on sale Oct. 12.

The HTC Amaze 4G smartphone.

T-Mobile will sell the HTC Amaze 4G for $259.99 and the Samsung Galaxy S II for $229.99. Both prices are after a $50 rebate and with a two-year contract.

They will be the first T-Mobile's smartphones to run on the carrier's HSPA+42 4G network, which has a theoretical top download speed of 42Mbps. T-Mobile said average downloads on the network approach 8 Mbps.

What most distinguishes the devices, however, is the Qualcomm Snapdragon S3 chip, a 1.5 GHz dual-core processor. The Amaze runs Android 2.3.4, also known as Gingerbread, while the Galaxy S II runs Android version 2.3.5.

Both phones support near field communications technology, which is being used for emerging mobile wallet in-store purchasing.

Pre-sale online orders will begin Oct. 10. The devices are expected to be in T-Mobile stores and other retailers Oct. 12.

The Amaze will be a T-Mobile exclusive. It features an 8-megapixel camera and a full HD 1080p camcorder, with an embedded video editor. It comes with a 4.3-in. touchscreen.

The Samsung Galaxy S II from T-Mobile.

Samsung said the Galaxy S II for T-Mobile has a 4.52-in. touchscreen, the largest of any sold by T-Mobile. Worldwide, Samsung has sold 10 million Galaxy S II smartphones, the company said, although there are some variations in the device across countries and carriers.

This Galaxy S II from T-Mobile offers even greater processing speed than the Galaxy S II Epic 4G Touch from Sprint , which has 1.2 GHz dual-core processing.

Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen or subscribe to Matt's RSS feed . His e-mail address is [email protected] .

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