Authors have a lot of fun with the possibilities. Most of the examples below are not hard science fiction. At the very minimum they will likely still be unable to eat the same food as humans (averting No Biochemical Barriers in the process), even if everything else in the setting can. These 'Siliconers,' if you will, are weird in some other way, or perhaps even par for the course when compared with all the other carbon-based aliens in the setting. Furthermore, silicon isn't even absolutely necessary for the building of a computer in the first place any material that can be used to make a wire will do, it's just that Silicon is the most practical material to use. They aren't anything-based, as there are no internal chemical processes in the first place. Note however that while Mechanical Lifeforms are potentially plausible, calling them 'silicon based' would be a case of Critical Research Failure while computers do use a lot of silicon at the current technological stage, they aren't silicon- based in the same sense that Earth life is carbon-based.

They might've been built at some point in the past, or evolved naturally. Mechanical Lifeform: As the name suggests, you're dealing with a planet of Robots and Machines here.

Formz sci fi