It requires significant energy to manufacture and deploy computational devices. Traditional discussions of the energy-efficiency of compute measure operational energy, i.e.\ how many FLOPS in a 50\,MW datacenter. However, if we consider the true lifetime energy use of modern devices, the majority actually comes not from runtime use but from manufacture and deployment. In this paper, then, we suggest that perhaps the most climate-impactful action we can take is to extend the service lifetime of

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... xisting compute. We design two new metrics to measure how to balance continued service of older devices with the superlinear runtime improvements of newer machines. The first looks at carbon per raw compute, amortized across the operation and manufacture of devices. The second considers use of components beyond compute, such as batteries or radios in smartphone platforms. We use these metrics to redefine device service lifetime in terms of carbon efficiency. We then realize a real-world "junkyard datacenter" made up of Nexus 4 and Nexus 5 phones, which are nearly a decade past their official end-of-life dates. This new-old datacenter is able to nearly match and occasionally exceed modern cloud compute offerings.