We have established that the CPU is a complex piece of hardware that does all sorts of tasks. It processes all the data that enters and leaves your computer. But where does the CPU store its computations?
The CPU utilizes something called “registers” to store computations. It serves as a form of temporary memory for the CPU. It is very fast but also tiny. There are many different registers, such as data registers that hold numeric data, status registers that hold truth values, and address registers that store addresses. Those are only a few examples. Different registers have different tasks and hold different data.
Where does the CPU store its computations after the register? It does to the cache and system RAM. You might be confused about what the difference between the CPU cache and the register is. You can think of the register as something that comes before the cache. There are a few differences. First of all, registers are much faster and are only used to store and retrieve specific data. Second, registers can be used more than once during one clock cycle.
If you wish to learn more about registers and the difference between them and cache, then you will find all the information you seek down below.
Where Does The CPU Store Its Computations?
Now that we have established that the CPU stores its computations primarily in registers and then cache, it is time to go into more detail about it. A CPU most commonly has 8 general-purpose registers. The register is proportional to the CPU’s architecture. If you have a 64-bit CPU, then your registers are 64 bits as well. There are also half-registers that are used for shorter instructions.
So how do all these CPU registers work? Let’s look at index registers for example. Index registers (address registers, registers of modification) are the most used type. The address of something inside a computer always includes a base, index, and other relative addresses. all of which are stored in the address register.
What is the difference between registers and cache? There are many differences. First of all, we need to explain what CPU cache is. Cache is very similar to a register in the sense that it holds data and that it is located in the CPU. It is a type of volatile memory that the CPU uses to store data. Most CPUs have three independent caches:
- instruction cache
- data cache
- translation lookaside buffer
Data cache is the one that CPU manufacturers boast about. Data cache can be further divided into levels (L1, L2, L3 on most modern CPUs). The difference between the levels is the speed and size. While L1 is the fastest and smallest, L3 is the slowest and biggest. This is the temporary storage that the CPU uses to input and fetch data that it might need again. You can think of cache as super fast memory that is next to the CPU chip. The register, on the other hand, can be thought of as an “L0” cache level.
A register is significantly smaller and faster, even when compared to L1 cache. Data registers can only hold some calculations and partial results. For example, when multiplying, a register stores the intermediate results and calculations while the processor is calculating up until it gets to the final result of the multiplication.
Both registers and cache are very important parts that cannot be ignored. Without one of them, CPUs would be extremely slow and inefficient. If the CPU did not have cache, it would have to fetch data from RAM and lose precious nanoseconds.
Conclusion
So, next time someone asks you, “Where does the CPU store its computations?“, you will know that the answer is a CPU register. You would not be mistaken to say that it is cache as it also plays a crucial part. The CPU needs registers to hold and fetch small amounts of data very quickly. It also needs all the different levels of cache that can hold significantly more data than registers.
The difference between the two is that registers are faster and closer to the actual chip. The similarity is that they are both significantly faster and closer to the CPU than the system memory (RAM). Also, both of them reside within the entirety of the CPU chip.
