This CPU won't be seen very often. Most people either bought the SX/DX33 or went for the DX2/66MHz. The DX2/66MHz was quite powerful and noticeably faster than the DX2/50MHz and thus worth the extra cash.
The SX2 doesn't have an integrated floating point unit (FPU) like any other 486SX CPU. Besides that it is exactly the same as the DX2.
To get a higher clock frequency the SX2 and DX2 use a technique called 'clock doubling'. This involves a multiplier that sets the clock frequency at twice the frequency of the front side bus (FSB). In this case a SX2/50 uses a 25MHz FSB and the CPU itself runs at twice the speed. The DX2/66 uses a 33MHz bus and weirdly enough the DX4/100 uses a 33MHz bus as well. Marketing-wise the name DX4 sounded better than DX3 but technically the DX4 is actually clock tripled like the non-existing DX3 would be.
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