Can CPU Access Hard Disk Directly? – Detailed Guide In 2023

With the development of technology, the question Can CPU Access Hard Disk Directly have become increasingly prominent in recent years, with the increasing prevalence of solid state disks, it must be asked: why do we still need RAM?

This question often comes to our mind when we are trying to speed up the PC, e.g. by adding more memory to improve performance or using SSDs instead of HDDs to shorten access time. But this may lead to confusion because nowadays CPUs and HDDs are built into one chip (aka SoC = System On Chip).

What if they share the same cache memory? Will it change anything or not?

In this article, we will learn if the CPU can access the hard disk directly without RAM. If it could, how much benefit and shortcomings would it bring to the system?

Can CPU Access Hard Disk Directly?

No, the CPU cannot access the hard disk directly. The hard disk is connected to the motherboard via a storage controller (RAM e.g.), which is responsible for managing data transfers between the hard disk and the CPU.

The storage controller is typically integrated into the motherboard chipset, but it can also be a separate card that is installed in a slot on the motherboard.

Using magnetic platters, hard disks store data mechanically. A CPU can access the hard disk directly without any additional hardware. However, there are two main challenges for the hard disk: data transfer speed and physical size.

As the capacity of the hard disk increases, its transfer rate decreases. Additionally, the physical size of the hard disk also limits its use in small devices like smartphones and tablets. Therefore, it is essential to have good data transfer speed and low power consumption when using a hard disk.

Despite the fact that it is possible to access a hard disk directly, it is still pointless.

What Is RAM And Why Is It Still Important?

When people ask if the CPU can access the Hard Disk without RAM, they often forget that the first thing we need to understand is “where does RAM fit into the system”? RAM is the fastest memory medium in terms of both reading and writing data on the computer.

This is because it is an electrical circuit that uses transistors to store data as binary zeros and ones, unlike a hard disk which uses magnetism to store data and therefore is much slower in comparison.

RAM is volatile storage that is used as a short-term workspace for the CPU to execute instructions and load data. The most important thing to know about RAM is that it loses the data when the power is switched off or when there is a sudden surge in power!

So the data in RAM is only available while the computer is on, or (as in the case of Windows computers) while the computer is in sleep mode.

How Does The CPU RAM And Hard Drive Work Together?

CPUs, RAMs, and hard drives are all parts that work together for the purpose of sending and receiving data from one another.

The CPU processes the data and sends it to the RAM for temporary storage while it is being processed. And after processing the data is stored permanently on the hard drive.

Whenever the processing is needed on the stored data, RAM gets data and sends it to the CPU.

Is SSD Primary Memory?

No, an SSD is also a secondary storage device. It is a type of computer storage device that uses integrated circuit assemblies as memory to permanently store data, rather than hard drives that use magnetic media to store it.

As opposed to traditional hard drives that store data on spinning disks, SSDs are a newer technology, which stores information on flash memory.

As SSDs use less power and are faster at accessing data, they can last longer on batteries due to the longest idle time.

Moreover, SSDs are much more robust than HDDs when it comes to physical shock and vibration.

However, SSDs are more expensive per gigabyte than HDDs, so they are often used in applications where speed or durability is more important than cost per gigabyte.

What Is NVMe SSD Technology?

Non-Volatile Memory Express (NVMe) is a protocol for accessing high-speed storage media, specifically solid-state drives (SSDs), over a computer’s high-speed PCIe bus.

Due to SSDs’ low latency and parallelism, NVMe was introduced in 2011. It is the successor to the AHCI storage protocol. With NVMe, storage controllers do not need to be separate as they operate at the host controller level.

By doing so, NVMe SSDs are much faster than traditional SAS or SATA SSDs.

NVMe also supports multiple queues, allowing multiple commands to be processed simultaneously.

NVMe is an open standard, with numerous companies offering compatible products. The most common form factor for NVMe SSDs is the M.2 card, which can be used in laptops, desktops, and servers.

Does NVMe Use CPU Lanes?

Yes, NVMe uses CPU lanes. This is because NVMe is a high-performance storage protocol that requires a fast connection to the CPU.

As it is embedded (connects directly on the motherboard) on the motherboard, it operates at high speeds. However, it is expensive so most people prefer SSDs.

Keep in mind, it cannot be used as RAM because even DDR3 is much faster than NVMe.

Which Device Can Be Accessed Directly By The CPU?

It is possible for the CPU to directly access the hard disk by using the Direct Memory Access (DMA) Controller.

This allows for data to be transferred directly between the hard disk and the CPU without having to go through the system memory. However, it is not really considered direct access.

This can greatly improve the performance of the system as it eliminates the need for data to be copied from one location to another.

Can CPU Access Secondary Memory Directly?

There is no direct access to secondary memory by the CPU, as this would be overly complicated. It must go through the computer’s bus structure to get to the hard disk.

The bus consists of a set of parallel wires that carry data between the different components of the computer. The hard disk is connected to the bus and the CPU can access it through the bus.

Conclusions:

I hope you found this article helpful in understanding the relationship between a CPU and a hard disk. While a CPU cannot access a hard disk directly, it can indirectly access it through RAM and other onboard devices.

I would love to hear if you have any more questions about this. Feel free to leave them below in the comments section if you have any.