Thoughts on software-defined silicon

> When you couldn't power all the transistors on the chip simultaneously for thermal reason the ability to pick between features A, B, and C (either of which can be enabled but not all simultaneously) make such scheme pretty attractive. You couldn't do that with millions of SKUs but can easily achieve with million of [potential] licenses.
> And in that case the ability to enable features without license would become actively harmful: enabling all features simultaneously would just fry the chip

Yes, but... modern chips have been past this point for at least a decade. It wasn't solved with a licensing system: it was solved by having power management circuitry on the CPU that adjusted things (usually the operating frequency and voltage, but it is perfectly possible to imagine it also adjusting semi-invisible microarchitectural features like the number of execution ports) such that your code would keep running, just slower. Boost mode etc is the same thing: the fewer cores busy, the faster they're run, and even with lots of cores busy you can run fast briefly until the power management system turns down the CPU frequency to keep things cool enough. This is obviously *vastly* more efficient and flexible than some clunky licensing system would be: it allows for dynamic adjustment, which is something no licensing system like this could ever handle.

No, this is all about getting to make one SKU and sell it as several and allow upselling lower models to higher without needing hardware replacement. Shame that doing so requires cryptographic locks in the chip. (I doubt that anticircumvention measures are meaningful here: modern CPUs are almost impossible to analyze at the level you'd need to to crack this open anyway, or people would already have extracted much more significant private keys for firmware signing etc. Nobody has.)