The System/360 machines were typically leased, not sold. And the leases had different tiers for different clock speeds. If you decided you needed more power, you'd call up IBM, accept a more expensive contract, their service rep would show up, unlock a padlock on the machine, open a panel, turn a knob, close and lock the machine again, and leave.
Indeed it feels like that - Intel makes only one part, sells it at one price and, if you want to enable the dark silicon, you pay Intel for a key and the feature is enabled.
It's better than what they used to do, when they killed parts of the CPU to match the SKUs they needed to sell. At least you can pay Intel to enable things.
> when they killed parts of the CPU to match the SKUs they needed to sell
Or that part of the CPU was dead to begin with; every wafer of silicon has some defects, but if these defects hit a part of the chip they can disable, they can avoid wasting a whole chip. Of course, if there's high enough demand for the SKU without that part, and low enough demand for the SKU with that part working, they might kill that part even when it's defect-free.
(Of course, if the part can be enabled "on demand", it means that the disabled part must be working, so they cannot be reusing partially defective chips; it smells like a cash grab.)
OTOH, if all I need is a powerful CPU and I have no use for any of the accelerators right now, I can pay a lower price than I would be able to, without Intel needing to make a different part for me.
For Intel, it also helps to fine tune the product lineup by getting more detailed usage information.
Price elasticity will play a role here, but, all things equal, you'll get a slightly better part than the one you'd get with the units permanently disabled.
CoD was just the expansion to Power-based systems.