Where Does the CPU Store its Computations? Explained [2023]

The CPU, also known as the processor, is the most critical part of a computer that processes all instructions received from the hardware and software running on the computer. It is also responsible for the retrieval and execution of instructions and all other computing operations. If you refer to the CPU as the “brain” of the computer, it won’t be wrong. Without a CPU, we cannot run programs and perform any tasks on a computer. So, you have to ensure that it works properly without lagging in any situation for better results. 

As we all know, the CPU is responsible for reading data and instructions from memory and then storing the results. So the CPU performs multiple computations in a second. You must know where does the CPU store its computations to better understand it. This may be a difficult task, but we’re here to make it easy. In this article, we’ll discuss where the CPU stores computations and give an overview of what “compute” is. We’ll delve into the instruction cycle and its components while explaining several other concepts.

What is a computation? 

By definition, computation is just the act of mathematical calculation since basically all CPUs are digital processors. When you give a CPU instruction, the CPU processes the instruction and stores the outputs as a string of 1s and 0s – binary code. In addition, the CPU consists of logic gate transistors with two values, yes and no, which is another way to look at the 1s and 0s. The way binary code is converted is that yes means one, and no means zero—binary code is the primary language of computers.

Where does the CPU store its computations? 

The CPU, or central processing unit, stores its computations in registers, a unique type of memory storage made explicitly for the processor. Many tech enthusiasts often think that the RAM or cache stores the CPU computations, which is not the whole truth. Well, RAM takes instructions from the storage that further delivers to the CPU cache. And from here, registers take those instructions and store them for the processor. In short, RAM, cache, and registers all play a direct role in the CPU instruction. But registers are the end-part where computations are being stored. Therefore, we say that it primarily stores the CPU computations. 

What is Register memory? What does a register do?

The level of the register is lower than that of the cache, which can be considered the L0 cache level. Registers are much smaller and faster than L1 cache. Most data registers can hold only a few calculations and partial results. For example, when multiplying, registers will store intermediate results and calculations while the CPU calculates until it gets to the final result. Another thing to notice is that the registers store the operational data that the CPU has processed. These are more likely the results of the previous operations that will be used in future operations. 

Registers are basically not the direct memory part, and instead, they are unique auxiliary memory locations that provide speed benefits over the actual cache. They work by holding, transferring, and performing arithmetic comparisons at high speed under the direction of the control unit. When the CPU is instructed to perform calculations, it retrieves data from larger memory and stores them in registers for easy access. So these are freed when a new computation is started. In addition, the function can be determined according to the class of the register. 

What are the types of registers?

Not all registers store calculations and similar values. They are divided into seven different categories based on their utility in processing. Let’s look at each of them:

• Accumulator: An accumulator is a basic and frequently used register that is a type of data storage memory. These vary in number among the various processors.
• Memory Address Registers (MARs): As the name suggests, these registers store the memory addresses used to fetch data to the CPU. Typically, these are parallel load registers that primarily hold the next memory address that needs to be manipulated.
• Memory Data Register (MDR): This register stores the data that needs to be written or fetched from a given location. Also known as a memory buffer register, it is used to store data for the next clock cycle.
• General Purpose Registers (GPRs): Modern CPUs have GPRs for storing temporary data during ongoing operations. The assembler can access the information stored in these registers.
• Program Counter (PC): As the name suggests, this register keeps track of program execution by holding the address of the next instruction. Sometimes, it also has a function to count the number of instructions.
• Instruction Register (IR): PC holds the address of the next instruction, and IR holds the instruction to be processed. Instructions from the PC are fetched from memory and stored in the IR so that the CPU starts executing when the PC points to the next instruction.
• Condition Code Register (CCR): Stores the current value of the condition code. It has five flag bits, which are set by the ALU (Logical Arithmetic Unit) to hold information about the operation just performed. These can be carry (C), overflow (V), zero (Z), negation (N), and extension (X).

What is CPU cache? How is the CPU cache different from the registers? 

The difference is that registers are built closer to the CPU and are only used to store and retrieve specific information. Unlike caches, registers can be accessed multiple times per clock cycle. Both registers and caches are essential, and without either of them, the CPU would be very slow and inefficient. For now, you can consider the register as faster cache memory. But some people think that the registers are something that sits before the CPU cache. To understand these differences further, we need to explain what a CPU cache is.

A CPU cache is a type of volatile memory, volatile means it erases what is stored in it when power is lost. The opposite applies to non-volatile memory. This type of memory does not forget data until it is overwritten. The cache is built close to the CPU cores for speed and easy access. The cache usually consists of three levels, L1 cache, L2, and L3—some processors may have a single-level cache. Anyhow, all three levels have specific functions, and they are configured differently. The CPU uses temporary storage to enter and fetch data it may need again.

• Level 1 cache: The cache at this level has the smallest capacity but the fastest speed. This is where critical CPU instructions are stored for faster access.
• Level 2 cache: The second cache level is a nice middle ground, with moderate capacity and moderate speed. This is where less important CPU instructions are stored but will still benefit from fast access speeds.
• Level 3 cache: The third and last cache level has the highest capacity but is much slower than the other levels. This is where frequently used paths, such as application paths, are stored to increase CPU usage when accessing frequently used data.

What is the role of RAM in CPU computation?

RAM is the separate temporary hardware storage used to store operating system files and other applications. It takes those files or instructions from storage devices like SSDs, HDDs, or other secondary storage to reduce buffering time and ensure smooth performance. Caches and registers are the internal memory of the processor or CPU, while RAM is external memory but all stores instructions. Therefore, the CPU does not use RAM to store computations. However, it retrieves larger data that would otherwise be accessed again and again. All in all, RAM does the same job as cache.

Conclusion

A processor is an integral part of the computer since it supervises all ins and outs of the system. You must know how the CPU stores its computations so you can better understand its working and importance. For your information, the CPU computations are stored exclusively in registers. However, you wouldn’t say that computations are stored too far in the CPU cache, as that also plays a vital role. Your CPU needs registers to save and fetch small amounts of data very quickly. It also requires different cache levels to hold data since these cache levels have much higher capacity than registers.

The difference between the two is that the registers are faster and closer to the actual chip, so they are also crucial for the processor to operate. The similarity is that they are both faster than RAM and integrated closer to the CPU. Also, they both reside in the actual CPU itself. But the caches are larger and slower than registers, which is why registers are used to store the most critical data needed for operations. Registers typically store data or instructions that the CPU can use to accomplish its tasks. Your CPU needs registers and caches to be as fast and efficient as possible.

Arslan Ashraf

CPUs & CPU Cooler Expert

Arslan Ashraf is a dedicated tech writer with a rich background in Computer Science and five years of experience in the field. While pursuing his Bachelor's degree from Virtual University, he has honed his expertise in CPUs and CPU Coolers. His ability to simplify complex technological concepts has made him a valuable resource for a wide audience. Driven by passion, Arslan remains at the forefront of industry trends, delivering expert insights that continue to enlighten his readers.