Way back when I had an iPhone 4, I tried running the chess program Stockfish on it in analysis mode, and it was examining around 250,000 nodes per second, which at the time seemed to me to be pretty good for a handheld device. This was not as good as my desktop, but still a good substitute for it. Two years later when I got the iPhone 5, the speed had improved to around half a million nodes per second. Two years after that with iPhone 6+ I was impressed to reach a million nodes per second. However, I have just upgraded to the iPhone 6s+, which is a three year old phone, and the same Stockfish program on this phone is examining an amazing two million nodes per second.
Compare this to my late 2009 iMac with a quad core 2.8 ghz core-i7 processor. For its day it was a top of the line desktop computer, but today it is about average. Using one core, the Stockfish program examines around 450,000 nodes per second. If I use all 4 cores then the program sees about 1.5 million nodes per second. The iPhone 6s+ only has two cores, but it is outperforming my desktop computer by a good margin.
Since the iPhone 6s+ came out, Apple has released the iPhones 7, 8, 10, and 10s, all of which are faster than the previous generation. (The 8 and 10 are part of the same generation.) The 10s is only slightly faster than the 10, because we are reaching a point where the laws of physics won't allow them to make the circuits smaller, therefor faster. I personally wanted an iPhone 10 or an iPhone 8, because I knew that the processor on those phones kicked ass, but I didn't want to spend a fortune for a phone, so I settled for the good enough iPhone 6s+, which I got on a Black Friday sale for $300.
Speaking of kicking ass, Apple has been doing that with their processor development. No other mobile phone manufacturer comes close. Apple is using a 7 nanometer process with their latest phones and tablets. Compare that to Intel, the world's largest microprocessor manufacturer, who recently backed off of their 10 nanometer chips because of problems and instead released 14 nanometer chips. AMD, who is already kicking Intel's butt, is scheduled to release 7 nanometer chips early next year, with a whole new line of processors that undercut Intel on price.
This is an exciting time because of how much progress has been made in computer processing power. It is also impressive how much power Apple has been able to put in mobile devices. The latest iPad Pro's, which use the same processors as their latest phones, outperform many desktop computers.