It’s widely believed that the main cause of the Yellow Light of Death is due to the processor getting so hot during heavy use of the console that the tiny solder points on the GPU liquefies, and over time loses its connection with the motherboard.
Older PS3s tend to be more vulnerable to YLOD and it’s believed that this may be due to older less efficient processors that generate more heat than the newer PS3 models. The official line from Sony however is that the yellow indicator warning light can be caused for a variety of reasons, without giving any further explanation.
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