I worked for a place that did something akin to this in the early 2010s. Someone figured out how to add 32-bit company laptops to the virtualization cluster (likely because they were using one as a stand in for a server that at the time would have been in the works but not yet purchased) and so once that work had been incurred they just kept "retiring" unserviceable company laptops to the cluster. Imagine a standard wire metro-rack crammed in a telecom closet beside a normal server rack. Now imagine that metro rack literally full of Toshiba Satellite Pro's from about 2005-9. The cluster hosted virtual machines for testing.

No fires, no hardware problems. No special cooling other than the mini-split that was in the closet to cool the server rack. They just kept trucking. But modern hardware is much more high strung and I don't doubt you'd have weird failures.

Edit: Back then VMs were how things were done and RAM was seemingly always the bottleneck by a mile, so the cluster did add up to a meaningful amount of extra performance compared to not having it.