What exactly was Nintendo thinking, underclocking the Super FX

>>3697202
>draw too much power from the cartridge slot
>fry people's consoles

>>3697293
This is an issue with the SuperFX. The dev manual states that certain peripheral devices, such as the multitap, can't be used with the SuperFX because it exceeds the current ratings of the SNES.

However, I doubt that the first gen SuperFX was clocked at 12MHz for that reason. Something tells me it had more to do with concerns about stability or something.

When a new CPU model is first being manufactured, it's common for a certain percentage of chips produced to be unstable when running at the highest "supported" clock speed, but run perfectly fine at a slower clock speed. For example, this is why you'll see multiple variations of an i5 that differ only in clock speed today, since the chips that failed manufacturer testing while running at the highest clock speed can simply be clocked down and sold as a cheaper option instead of being discarded. It's also the same story with 3-core or 6-core CPUs: They most likely came off the same assembly line as the corresponding 4- or 8-core chip but bad one or two bad cores disabled before shipping, and those cores can usually be reenabled in your computer's BIOS.

The manufacturing process for that chip generally gets improved over time to a point where they can more reliably make chips that run full speed without problems, so it's likely that they went with 12MHz early on then upgraded to 21MHz at the end since that was the yield they had to work with.

Alternatively, process shrinking allowed them to make a faster chip that ran without overheating near the end of the chip's lifespan (less likely since die shrinks usually entail significant changes to the manufacturing process, same reason why they only happen every few product cycles with modern CPUs).

>>3697296
I'm pretty sure that current draw was exactly the reason. Frying consoles is bad. Until they got real world data they probably weren't willing to push it.

>>3697202
It was an early version of the chip, they weren't sure it could be clocked to 21mhz at the time. In fact it probably wasn't.

>>3697303
This.
The practice is called "binning"

>>3697296
Were earlier SuperFX chips produced on a larger process like 800nm and then proved to a smaller process like 500nm when it became available?

That would decrease powr usage and heat allowing for a faster clock speed.