If you are building a system on a budget, AMD is currently the king of the low cost machine.  For a mere $55 you can grab the dual core, four thread, 3.2 GHz Athlon 200GE and it's three Radeon compute units, add in a motherboard for the same price, a spare SSD and the only major remaining cost would be the DDR4.  The Ryzen 3 2200G is a better performing chip overall and is unlocked but it costs twice as much and might not be needed for some builds as you can game quite comfortably at 720p with the 200GE as Techspot demonstrates in their review.

"AMD's most affordable Zen based processor yet, the Athlon 200GE is just dual-core, but before your shrek louder than the coil whine of a cheap graphics card, consider the price, this is a $55 processor."

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Processors