How many billions of transistors in an iPhone processor?

What are all those transistors doing?

I've heard the cache is the biggest part. Per https://en.wikipedia.org/wiki/Apple_A17, the A17 has 72MB of cache. Cache is typically SRAM. Per https://en.wikipedia.org/wiki/Static_random-access_memory, a single bit of SRAM typically uses 6 transistors, but it could be anywhere from 4 to 10. So that's between 2.3B and 5.7B transistors for the cache.

That leaves about 1B transistors for each of the 12 cores (6 CPU + 6 GPU). The instruction set is a few hundred instructions. Surely it doesn't take millions of transistors to implement each instruction. Other than the cache, which parts of the processor need millions of transistors?

> I don't think it has less meaning than the idea that the most sere and hostile environment for our species that we've yet been able to access - the deadliest imaginable desert, accessible only at vast effort and expense - has for our taking the boundless cornucopia of riches that space maximalists constantly promise, and with no more support than you complain I offer.

We've already benefited greatly from just the process of trying to get there. Even if there is no "riches" to be had in terms of extracting resources from alien planets, we still gain from our endeavors. This can be indirectly through technological advancements made in service to that mission (which we've seen plenty of already), or it can simply be in the pursuit of knowledge in the understanding of our universe.

> Meanwhile you blithely argue that some significant fraction of a trillion dollars, available in this happy counterfactual from what had been the war department's budget, should be devoted to this and nothing else, with no thought to the opportunity cost - and demand I justify myself in arguing we should better do otherwise!

Why do you assume that there is not thought to the opportunity cost? It's quite clear that we have different priorities on how humanity should allocate its resources but to say that it's not a consideration is just crass. The amount of human productivity we dedicate towards space exploration is a remarkably small percent of what's available, and a lot of that is driven by individual's interest in it.

The space program's budget is minuscale compared to what we spend elsewhere, maybe around 5% of a trillion dollars. That's a significant amount of money, but you seem to think that could be better spent on... what, exactly? Let's say we reallocate that budget to social security. That'd be adding less than 4% to its budget, which is already over a trillion dollars. Or the combined spend of medicaid and medicare, in which case it would be less than 3%.

> That opportunity cost would be measured in human lives, consigned to neglectful death in the service of your cause

A lot of things have indirect consequences, positive and negative. Many things that have dramatically improved the livelihoods of humanity have come at a great cost.

> but whether by neglect or murder, dead is dead. You'd be far from the first so to act; history is replete with examples, even ignoring the one we live among now. Such people are sometimes called to account. What would you say if you were?

The advancements made by curious people has made the world less impoverished and less "dead." Even if 100% of human productivity was allocated towards protecting human life, people will still die. That is life. At what point in your hypothetical world where you got to make these policies would it be acceptable for humanity to start exploring space again? When humans stop dying?

Humanity's driven by curious people willing to explore well beyond what seems rational to most people, not myopic luddites who would eschew entire avenues of exploration simply because they can't understand the utility in it.

I'm out of date by a couple of years, but the last I knew, the ARM Architecture Reference Manual (amusingly, also called the ARM ARM) is around 8000 pages. Though, it carries similar corpus from the ARMv7 manual, now bottled as AArch32.

> A billion is a tough number to understand

I love using the money analogy for this:

"If you earned $1 every single second, that's $60 per minute, $3,600 per hour, $86,400 per day. More than most people make in a year!

Assuming no tax or expenditure whatsoever, it would take only 11 days to become a millionaire at that salary.

It would take over 31 _years_ to become a billionaire.

And that's only a mere $1 billion, some people are worth _hundreds_ of billions."

Some people might be wondering "huh, why number them in this weird way?!"

It's because they were originally 3 volumes. volume 2 is the ASM reference, 3 is the "how to do things" reference (System programming guide). Volume 1 is more of a general reference so maybe that's why it didn't grow so much.