[eru]

During the 1990s (and for some years before and after) we got 'Dennard scaling'. The frequency of processors tended to increase exponentially, too, and featured prominently in advertising and branding.

I suspect many people conflated Dennard scaling with Moore's law and the demise of Dennard scaling is what contributes to the popular imagination that Moore's law is dead: frequencies of processors have essentially stagnated.

See https://en.wikipedia.org/wiki/Dennard_scaling

[timschmidt]

Yup. Since then we've seen scaling primarily in transistor count, though clock speed has increased slowly as well. Increased transistor count has led to increasingly complex and capable instruction decode, branch prediction, out of order execution, larger caches, and wider execution pipelines in attempt to increase single-threaded performance. We've also seen the rise of embarrassingly parallel architectures like GPUs which more effectively make use of additional transistors despite lower clock speeds. But Moore's been with us the whole time.

Chiplets and advanced packaging are the latest techniques improving scaling and yield keeping Moore alive. As well as continued innovation in transistor design, light sources, computational inverse lithography, and wafer scale designs like Cerebras.

[eru]

Yes. Increase in transistor count is what the original Moore's law was about. But during the golden age of Dennard scaling it was easy to get confused.

[timschmidt]

Agreed. And specifically Moore's law is about transistors per constant dollar. Because even in his time, spending enough could get you scaling beyond what was readily commercially available. Even if transistor count had stagnated, there is still a massive improvement from the $4,000 386sx Dad somehow convinced Mom to greenlight in the late 80s compared to a $45 Raspberry Pi today. And that factors into the equation as well.

Of course, feature size (and thus chip size) and cost are intimately related (wafers are a relatively fixed cost). And related as well to production quantity and yield (equipment and labor costs divide across all chips produced). That the whole thing continues scaling is non-obvious, a real insight, and tantamount to a modern miracle. Thanks to the hard work and effort of many talented people.

[eru]

The way I remember it, it was about the transistor count in the commercially available chip with the lowest per transistor cost. Not transistor count per constant dollar.

Wikipedia quotes it as:

> The complexity for minimum component costs has increased at a rate of roughly a factor of two per year. Certainly over the short term this rate can be expected to continue, if not to increase. Over the longer term, the rate of increase is a bit more uncertain, although there is no reason to believe it will not remain nearly constant for at least 10 years.

But I'm fairly sure, if you graph how many transistors you can buy per inflation adjusted dollar, you get a very similar graph.

[timschmidt]

Yes. I think you're probably right about phrasing. And transistor count per inflation adjusted dollar is the unit most commonly used to graph it. Similar ways to say the same thing.