What is physically different between a high-end CPU (e.g. Intel i7) and a low-end one (Intel i3)? What makes the low-end one cheaper?
In: Technology
Other than arbitrary pricing in a non-competitive market situation, the main thing that affects CPU pricing is the **number of non-defective CPUs per wafer**.
CPU manufacturing starts with a big cylinder of silicon. That cylinder is cut into discs, or wafers. That wafer is then engraved (via secret magics) with as many CPUs as they can fit. They can’t make bigger and bigger wafers, because that original cylinder of silicon still has to obey the laws of physics and thermodynamics and cools differently in the middle vs the outside. Imagine the difficulty of making a cupcake vs. a giant cake, where if you don’t do it juuuuuuust right, the outside will be burnt while the inside is still raw.
All else being equal, the more features a CPU has, the more transistors it requires, the more space it takes up on a wafer. More space = fewer CPUs per wafer. Furthermore, the more transistors a given CPU has, the greater chance of a defect being in there somewhere. Defects => fewer CPUs they can sell per wafer => higher costs.
The main high-level feature differences between i3, i5, and i7 CPUs are clock speed, # of CPU cores, and size of the cache. # of cores and cache are basically directly responsible for the size of the CPU on a wafer. An i3 with 2 cores and 256K of cache will take up far, far less space than an i7 with 8 cores and 8MB of cache. Less space means more CPUs per wafer means less cost per CPU.
Others have touched on the idea of binning where an i7 with 2 out of 8 defective cores is sold as an i5 with 4 cores or something like that, but that’s really secondary. Being able to make an i5 out of a partially defective i7 helps them recover waste from a wafer full of i7s, but that’s far, far less important than being able to get 2x as many i5s out of a single wafer of non-defective chips in the first place. As their manufacturing process improves, the defect rate gets lower and lower and they wouldn’t have enough defective CPUs to market to the more price-conscious consumers. Binning is much more likely to be used to sell lower-rated CPUs in the same general class.
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