What's Inside a Router?

The Main Parts at a Glance

The SoC: CPU Cores and the NPU

The system-on-chip is the heart of the router. It integrates multiple functional blocks onto one piece of silicon. The CPU cores, typically one to four ARM Cortex cores running between 700 MHz and 2 GHz in consumer devices, run the firmware operating system and handle any traffic that cannot be processed by dedicated hardware. However, running NAT and routing through a general-purpose CPU is expensive. A 1 GHz single-core CPU pushing millions of packets per second quickly saturates.

To solve this, most modern router SoCs include a network processing unit or hardware NAT engine. Qualcomm calls its implementation the Network Sub-System, or NSS. MediaTek includes hardware NAT and flow acceleration in its platform. These dedicated engines intercept established flows and forward them without CPU involvement, allowing the router to move gigabit or multi-gig traffic while the CPU sits at low utilisation. The NPU is the reason a modestly-clocked router CPU can still route at very high speeds for simple use cases, and why throughput drops sharply when features like VPN or SQM bypass that hardware path.

RAM: Why the Amount Matters

RAM in a router holds everything that must be accessed quickly at runtime: the NAT connection tracking table, firewall state, ARP and neighbor tables, DHCP leases, DNS cache, routing tables, wireless client association records, and any running services such as mesh coordination daemons, traffic analyzers, or VPN processes. A router with very little RAM runs out of table space under high client counts or many simultaneous connections. When the connection table fills, new sessions are dropped or old ones are evicted prematurely. The result looks like random packet loss or intermittent connectivity, especially under heavy peer-to-peer or streaming load. Most modern routers ship with 256 MB to 1 GB of DDR3 or DDR4 RAM. Budget models may use 128 MB, which becomes a practical constraint with custom firmware or many clients.

NAND and NOR Flash: Firmware Storage

Flash memory holds the router firmware image and the persistent configuration. Most routers use NAND flash, which is dense and inexpensive. Smaller and older routers sometimes use NOR flash, which is slower to write but faster to execute code from directly. The size of flash matters for two reasons. First, small flash, typically 8 MB or 16 MB on budget devices, limits the firmware image size and therefore the features the manufacturer can include. Second, small flash makes installing alternative open-source firmware such as OpenWrt difficult or impossible, since the firmware image may not fit with packages added. Flash also has a finite number of program-erase cycles. Consumer NAND is often rated at a few thousand cycles per block. For a router that writes logs and configuration infrequently, this is not a practical limit, but flash that has been written heavily or degraded by sustained heat can develop bad blocks that cause update failures or settings loss.

Wi-Fi Radio Chips

The radio chip generates the actual 2.4 GHz, 5 GHz, or 6 GHz radio frequency signals and handles all the PHY-layer processing: modulation, coding, channel bonding, beamforming weight computation, and spatial stream management. In many routers, the 2.4 GHz and 5 GHz radios are separate chips, sometimes from different vendors than the SoC itself. A tri-band router has three radio chips: one 2.4 GHz and two 5 GHz, or one 2.4 GHz, one 5 GHz, and one 6 GHz in a Wi-Fi 6E design. The radio chip's quality determines which Wi-Fi standards are supported, the maximum number of spatial streams, and the ability to use wide 80 or 160 MHz channels. High-end routers use premium radio silicon from Qualcomm or MediaTek that supports 4x4 MU-MIMO, while budget designs may use 2x2 radios with lower throughput ceilings.

The Ethernet Switch Chip

The LAN ports on the back of a router connect to a dedicated Ethernet switch chip, not directly to the SoC in most designs. This switch chip handles packet forwarding between LAN ports entirely in hardware at line rate, so transferring a file between two wired devices on the same LAN does not burden the router CPU at all. The switch chip also manages VLAN tagging, allowing the router to segment traffic between the WAN port, LAN ports, and internal interfaces. Budget routers often integrate a 100 Mbps or 1 Gbps switch. More capable routers include 2.5 GbE or even 10 GbE switch ports, but these require a switch chip that supports those speeds and a SoC with enough internal bandwidth to connect to it.

Power Supply Circuitry

The router receives power from an external AC adapter that steps mains voltage down to typically 12 V or 19 V DC. Inside the router, switching regulators convert that input to the multiple lower voltages the SoC, RAM, radio chips, and other components need, commonly 1.0 V, 1.8 V, and 3.3 V. The quality of these regulators and their supporting capacitors directly affects stability. Poor voltage regulation causes the SoC to receive noisy or slightly under-spec power, which can trigger resets or erratic behaviour under load. This is why using the correct power adapter, with the right voltage and sufficient current capacity, matters more than it might seem.

The Reset Button

The reset button connects to a GPIO pin on the SoC. The firmware watches that pin and responds to short or long presses differently: a brief press may reboot the router, while holding it for ten or more seconds usually triggers a factory reset by writing defaults back to flash. Some routers implement a multi-stage reset where a very long press clears the firmware partition, enabling a TFTP recovery mode for reflashing. This circuitry is simple but critical for recovery. A router that cannot be factory reset due to flash failure is effectively bricked.

How OEMs Choose Components and Why Flagship Routers Cost More

Router manufacturers choose components based on cost targets, feature requirements, and competitive positioning. A budget router might use a mid-range SoC, minimal RAM, small flash, and 2x2 radios to hit a price point. A flagship router uses a high-performance SoC with a capable NPU, 512 MB or 1 GB of RAM, 128 MB or more of flash, 4x4 radios with tri-band capability, multi-gig Ethernet switch ports, better power regulation, and more thorough thermal design. Each of those upgrades adds material cost. The price difference between a $60 router and a $300 router is almost entirely in the bill of materials: better silicon, more memory, higher-quality radio chips, improved power circuitry, and a more substantial enclosure with better thermal management.

Frequently Asked Questions

Is a router basically a small computer?

Yes. It has a processor, memory, storage, network interfaces, radio hardware, and a full operating system purpose-built for packet forwarding and wireless networking.

Do external antennas mean better Wi-Fi?

Not automatically. The radio chip quality, antenna engineering, placement, and firmware matter more than whether antennas are visible. Many compact mesh nodes with internal antennas outperform budget routers with prominent external ones.

Why do routers need cooling if they have no fan?

They run continuously and their SoC, radio chips, and power circuitry all generate heat. Passive cooling through vents, heat spreaders, and convection handles this in normal conditions, but poor placement or a hot environment can push temperatures high enough to cause throttling or instability.