Most of us have out PC fully assembled from day one. When I was a kid, I was overwhelmed by what a computer could do and I couldn't stop imagining what was inside that noisy "metal box". It was until high school when I chose a computer repair class and learned that it was just like pieces of lego that worked together.

Computers basically consists of two components: hardware and software. In this post we are only looking into the hardware part of the computer.

Hardware

Hardware could be categorized into two types: internal hardware and external hardware. Internal hardware is basically hardware inside the casing/housing that is directly plugged on to the motherboard; and external hardware is usually plugged on to the casing/housing of the PC.

I think most of us are familiar with the external ones, so let us jump in to the internal hardware and look inside the "metal box".

Motherboard

The motherboard acts as the backbone for all the other hardware. It basically distributes power to almost every components and allows communication between each other. In order to achieve that goal, all the other hardware should meet the slot specifications of the motherboard. The most important slots on the motherboard are the CPU processor socket, memory slots, and PCI-e. Then there are some other expansion slots and connectors such as, USB 3.0, HDMI and other display ports, etc. Some other features you would like to have is BIOS/UEFI settings, SSD caching, virtual graphics, multiple GPU support, overclocking, heatsink etc. Overall, know the specs, and try to get your best buck. Finally, make sure that the motherboard fits into your chasis if you have already bought one.

CPU

The CPU serves as the brain of the computer. It actually consists of two components: the arithmetic logic unit and the control unit. The measurement of work executed by a CPU (processes) is known as the clock rate (or clock speed). It is measured in gigahertz (GHz). This means that a 4GHz CPU could execute 4*10^9 cycles/sec.

Originally, CPUs only consist of a single core. Over time, CPUs became smaller and faster, and manufacturers decided to add more cores to the CPU, allowing them be more efficient. So, you could run two processes at the same time with a dual-core CPU, and four processes with a quad-core CPU etc.

There are two big names when it comes to the CPU: Intel and AMD. When it comes down to us, as consumers, we would want to know what are we buying. We could know it at a glance from
their naming system. The names of both Intel and AMD consist of the brand, modifier (or product line), generation indicator, and model. Most of us would understand the relationship of the branding + modifier and the specifications (i7 > i5 > i3 > Pentium and Ryzen 7 > 5 > 3); but don't understand what the numbers and letters at the back represent. The first number represents the generation of the CPU, and the next three are basically the SKU number for reference. The letters behind the numbers actually means the features of the CPU, and this would depend on the manufacturer. But for Intel, K stands for overclocking, H stands for high performance graphics, and Q stands for quad-core etc. So an Intel Core i7-8700K basically means that this is the 8th Generation chip of the Core i7 series and it supports overclocking.

RAM

A.k.a random-access memory. RAM is known as the working memory for the PC. So, when the
CPU is running a process, it needs a short-term memory to store the data that it is processing. This type of memory needs to be transferred at high speed and it is basically faster than HDDs and SSDs. Another fact is that the RAM is a volatile memory, which means that everything is lost when the power is off, since it is only meant for processing "short-term" data, it doesn't really matter. RAM these days comes in the Double Data Rate (DDR) standard. If you bought your computer before the year 2007, it would most probably be in DDR2 format. Today, most of the PCs are using DDR3 format. Do take note that different standards are not compatible with each other. This means that you couldn't put a DDR2 RAM in a DDR3 slot or a DDR3 in a DDR4 slot.

DDR Standard Data Rate (MT/s) Transfer Rate (GB/s)
DDR 266-400 2.1 -3.2
DDR2 533-800 4.2-6.4
DDR3 1066-1600 8.5-14.9
DDR4 2133-3200 17-213

GPU

A.k.a graphic processing unit. Back in the days, GPUs were only used for gaming, and they come in different formats (PCI and AGP). Today, a decent GPU not only provide a decent gaming
experience, it could be used for machine learning and crypto-mining.

First things first, make sure you have enough space for a new GPU. If you want to upgrade it,
make sure that your GPU could fit into the chassis. If you want to add another piece, make
sure it has another slot.

Most GPUs today come in the PCI-e format (this also goes for network cards and sound cards).
Although they may come in different sizes and versions, sometimes it is still compatible. So, before buying, we should understand what our motherboard (and chassis) is capable and compatible of.

PCI-e Sizes:

No. of Pins Length (mm)
PCl-e x1 18 25
PCl-e x4 32 39
PCI-e x8 49 56
PCl-e x16 82 89

The notch for foolproof on the PCI-e slot is always on the 11th pin. This allows a smaller PCI-e card to actually fit into a larger slot. Larger cards would only fit into a smaller slot only if the slot has an open end. All PCI-e versions are compatible with each other, no matter fowards or backwards. This allows you to upgrade your GPU without the need of changing a motherboard.

PCI-e Versions:

Bandwidth (per lane)
PCI-e 1.0 26bit/s (25oMB/s)
PCI-e 2.0 4 Gbit/s (5ooMB/s)
PCI-e 3.0 7.87 Gbit/s(924.6MB/s)
PCI-3 4.0 15.75 Gbit/s (1969 MB/s)

But, even though your GPU might be compatible with the motherboards PCI-e and fit well inside
the chassis, we still need to make sure if our power supply has enough headroom to provide
power to our GPUs.

Just like CPUs, the two big names in the GPU world are Nvidia and AMD Radeon. Just as CPUs, each of them have their own naming system, which are actually quite similar to the CPUs. The first part of the numbering indicates the generation, and the second part indicates the performance tier and revision related to given generation. The suffix letters "Ti" on Nvidia and "X" on AMD GPUs actually indicates the fastest version of the given model. So, a Nvidia GTX 1080Ti is basically the fastest of the 10th generation GTX GPUs.

Hard Disk

When we talk about hard disk storage, it always comes down to this question: "Should I buy an
SSD?" The difference between a HDD (hard disk drive) and an SSD (solit state drive) is basically size and speed. HDDs are relevantly cheaper in terms of GB/$. On the other hand, SSDs uses flash memory, which makes them way more faster than the magnetic counterpart. Most PCs today would recommend using a SSD for the system (speed and performance) and a HDD for
storage (mass storage).

There's a new form of memory storage these days known as M.2 SSDs. These have similar performances compared to the normal SSDs, but they are relatively smaller in terms of physical size. M.2 drives are divided into SATA M.2s and NVMe M.2s. The difference between the two is that the max speed for SATA III ports is only 600Mb/s, whereas NVMe uses the PCI-e slot of your motherboard which could theoretically run as fast as 6Gb/s (but, we won't be going that fast actually).

Speed
HDD 100 Mb/s (R/W)
SSD 500 ~ 600 Mb/s (R/W)
NVMe M.2 2.5Gb/s (R) 1.5Gb/s (W)

Power Supply

Most people don't really care about power. But if you're really into the building your PC, you should take note on the basic specifications for the PSU. The power supply is important because it is the source of electricity for everything inside the tower. The amount of energy needed for the PC is calculated in Watts (W). So, the question here is how much power (or watts) do we need for our PC? If we are buying lower than our wattage, it would cause sudden shut downs, lagging, or it might even fail to boot. On the other hand, buying a high wattage (1200W) power supply would be unnecessary for a low wattage (400W) PC. Not only is it expensive, it is inefficient, and would cause you more in the long run (electricity bills).