Raspberry Pi 4 Technical Specifications

Detailed hardware specifications for all Raspberry Pi 4 variants and models.

Summary Specifications Table

Processor (CPU)

Broadcom BCM2711

The BCM2711 is Broadcom's high-performance ARM SoC designed for the Raspberry Pi 4 platform.

Architecture Details:

• Instruction Set: ARMv8-A (32-bit and 64-bit support)
• Cores: 4 cores
• Core Type: ARM Cortex-A72
• Manufacturing Process: 28nm (TSMC)
• Clock Speed: 1.5 GHz base, boost to 1.8 GHz with frequency scaling
• Pipeline: 15-stage pipeline

Cache Hierarchy:

• L1-Instruction: 32 KB per core
• L1-Data: 32 KB per core
• L2 Cache: 1 MB unified (shared between all cores)
• L3 Cache: 512 KB system cache
• Total Cache: 1.5 MB

Power Characteristics:

• TDP (Thermal Design Power): 15W at full load
• Idle Power: 2-3W
• Typical Router Load: 12-15W
• Peak Power: 18-20W (all features active)

Frequency Scaling: The kernel supports dynamic frequency scaling (CPUFreq) with governor options:

• ondemand: Scales based on load (default)
• powersave: Minimum frequency (power saving)
• performance: Fixed at 1.8 GHz
• schedutil: Kernel scheduler-based scaling

Thermal Throttling:

• Throttle Point: 80°C
• Shutdown Point: 85°C
• Recovery Temperature: 75°C

GPU (VideoCore VI)

The Broadcom VideoCore VI GPU handles video output and offload operations:

• GPU Clock: 500 MHz typical
• Shader Cores: 12x QPU (Quadrature Processing Unit)
• Memory Access: Dedicated memory interface
• Video Outputs: HDMI 2.0 (dual on 8GB model)
• Video Decode: HEVC, H.264
• Video Encode: H.264

For router applications, the GPU is primarily used for:

• Video output (HDMI - minimal for headless routing)
• Hardware acceleration (possible future use)
• System monitoring

Memory (RAM)

Physical Configuration

The RPi4 uses LPDDR4 (Low Power DDR4) memory in two different physical configurations:

1GB/2GB Variants:

• Single 8Gbit (1GB) or 16Gbit (2GB) LPDDR4 chip
• Single-rank configuration
• Part Number: Micron MT53E256M32D4NQ-046

4GB/8GB Variants:

• Dual 16Gbit (2GB each) or 32Gbit (4GB each) LPDDR4 chips
• Dual-rank configuration
• Part Numbers: Micron MT53E512M32D4NQ-046 or Samsung K3QF4F40BM

Memory Performance

Speed and Latency:

• Memory Speed: LPDDR4-3200 (3200 Mbps)
• Bandwidth: 54 GB/s theoretical
• Memory Bus Width: 32-bit to LPDDR4 PHY
• Memory Controller: Integrated in BCM2711

Access Times:

• L1 Cache Hit: ~4 cycles (~2.7ns)
• L2 Cache Hit: ~10-15 cycles (~7-10ns)
• RAM Access: ~30-40 cycles (~20-27ns)
• Round-trip latency: ~200ns

Memory Configuration

GPU/CPU Memory Split:

The VideoCore VI GPU and CPU share unified memory. The memory split is configurable via /boot/firmware/config.txt:

• Headless Router Configuration (recommended):
  • GPU Memory: 128 MB (minimum for boot)
  • CPU Memory: Remaining (e.g., 3872 MB on 4GB model)
• System Configuration Command:

# View current split
vcgencmd get_mem arm    # CPU memory
vcgencmd get_mem gpu    # GPU memory

Memory Available by Model

Network Interface

Gigabit Ethernet

The RPi4 features true Gigabit Ethernet with a dedicated network path:

Physical Interface:

• Connector: RJ45 jack
• Standard: 802.3at PoE capable (with PoE Hat)
• Speed Options: 10/100/1000 Mbps auto-negotiation
• Link Negotiation: Auto-MDI/MDIX

Hardware Architecture:

• MAC Controller: Dedicated Gigabit Ethernet MAC
• PHY (Physical Layer): Integrated in BCM2711
• Connection: Direct PCIe connection (not shared with USB)
• PCIe Lanes: Dedicated Gen 2.0 x1 (5 Gbps theoretical)

Practical Performance:

• Observed Throughput: Excellent throughput for gigabit connections
• Line Rate: ~94% of 1000 Mbps (accounting for framing/protocol overhead)
• Latency: <1ms typical
• Jitter: <100µs under load

Power Consumption:

• Idle (link up, no traffic): ~200 mW
• Transmitting: ~350 mW
• Receiving: ~300 mW
• Full duplex: ~400 mW

Wireless Connectivity

2.4GHz and 5GHz Dual-Band Wi-Fi:

• Standard: 802.11ac (Wi-Fi 5)
• Channels: 2.4GHz (13 channels), 5GHz (25 channels, region-dependent)
• Bandwidth: 20 MHz (legacy), 40 MHz, 80 MHz
• Data Rates: Up to 433 Mbps (5GHz), 150 Mbps (2.4GHz)
• MAC Address: Burned into OTP memory (unique per board)

Bluetooth 5.0 + BLE:

• Range: 50-100m line-of-sight
• Data Rate: 2 Mbps (BLE), 1-2 Mbps (classic)
• Profiles: HID, DUN, A2DP, AVRCP
• Chipset: Cypress CYW43455

USB Connectivity

USB 3.0 Ports (2x)

Super-Speed USB high-bandwidth connectivity:

• Standard: USB 3.0 (SuperSpeed)
• Speed: 5 Gbps theoretical
• Connectors: Type-A (dual stacked)
• Actual Throughput: ~350 Mbps average (protocol overhead)
• Peak Burst: ~450 Mbps
• Use Cases: External SSD, high-speed storage, networking adapters

Current Limiting:

• Total USB 3.0 Current: Shared
• Recommended per port: 900 mA max
• All ports combined: Limited by power supply (3A total)

USB 2.0 Ports (2x)

Legacy High-Speed USB for peripheral connectivity:

• Standard: USB 2.0 (High-Speed)
• Speed: 480 Mbps theoretical
• Connectors: Type-A
• Actual Throughput: ~40 Mbps average
• Use Cases: Keyboards, mice, adapters, legacy devices

Current Limiting:

• Per port: 500 mA
• All ports combined: Limited by power supply

USB Controller Architecture

The USB subsystem uses VLI VL805 controller with dedicated PCIe connection:

• USB 3.0 Controller: VIA VL805 Chipset
• USB 2.0 Hub: Integrated into VL805
• Connection: PCIe Gen 2.0 x1 (shared with Ethernet via PCIe switch)
• Bandwidth: 5 Gbps shared for all USB + Ethernet

Storage Interface

microSD Card Slot

For primary OS and storage:

• Standard: SD UHS-II (Ultra High Speed)
• Compatibility: SD, SDHC, SDXC
• Speed Class: Up to UHS-II
• Data Bus: 4-bit parallel
• Speed: Up to 104 MHz clock
• Voltage: 3.3V

Recommended microSD Specifications:

• Capacity: 64GB-256GB (Class 10, A2 rated)
• Speed Class: Class 10 (10 MB/s minimum write speed)
• Application Class: A2 (1000 IOPS random read/write)
• Endurance Class: Video Class 30 (V30, 30 MB/s guaranteed)

Typical Performance:

• Sequential Read: 90-120 MB/s
• Sequential Write: 50-70 MB/s
• Random IOPS: 500-1000 (4KB operations)

USB 3.0 Storage (External SSD)

For logs, analytics, and advanced features:

• Interface: USB 3.0 (via USB 3.0 port)
• Protocol: UAS (USB Attached SCSI) or BOT (Bulk Only Transport)
• Typical SSD Speed: 400-550 MB/s
• Practical Throughput: Limited by USB 3.0 (~350 Mbps actual)
• Recommended: M.2 NVMe with USB 3.0 enclosure

GPIO and Interfaces

40-Pin GPIO Header

The RPi4 includes a 40-pin connector compatible with HATs (Hardware Attached on Top):

Physical Layout:

• Pin Count: 40 pins (2 x 20)
• Standard: Raspberry Pi GPIO specification
• Voltage: 3.3V logic
• Current per Pin: 16 mA maximum
• Total Current: 50 mA maximum all pins

Available Functions:

• GPIO Pins: 27 pins (configurable digital I/O)
• Power Pins: 8 pins (4x 5V, 4x GND)
• Specialized: SPI, I2C, UART, PWM
• Detection: ID EEPROM for HAT auto-detection

Serial Interfaces

SPI (Serial Peripheral Interface):

• SPI0: 4 pins (MOSI, MISO, SCLK, CE0/CE1)
• Speed: Up to 125 MHz
• Mode: Master only
• Use: Sensor interfaces, external storage, displays

I2C (Inter-Integrated Circuit):

• I2C0/I2C1: 2 pins each (SDA, SCL)
• Speed: 100 kHz, 400 kHz, 1 MHz modes
• Address Space: 127 unique devices per bus
• Use: Sensor fusion, expansion modules, monitoring

UART (Serial Communication):

• UART0: Primary serial (TXD, RXD, CTS, RTS)
• Speed: Up to 3 Mbps (default 115200 baud)
• Use: Console debugging, serial devices

PWM (Pulse Width Modulation):

• Channels: 2 hardware, 28 software
• Frequency: 1 Hz - 19.2 MHz
• Resolution: 32-bit programmable
• Use: Fan control, LED brightness, motor control

Video and Audio

Video Outputs

HDMI 2.0 (Standard RPi 4):

• Connector: Full-size HDMI
• Standard: HDMI 2.0
• Resolution: Up to 4K (4096x2160 @ 60Hz)
• Color: 10-bit HDR support
• Audio: PCM, DTS, Dolby Digital

Dual HDMI (RPi 4 8GB Model):

• Dual Outputs: 2x full HDMI 2.0 connectors
• Mirroring: Can mirror or extend displays
• Independent: Both can drive separate monitors simultaneously

Audio Output

3.5mm Jack (Stereo):

• Type: 3.5mm TRS jack
• Output: Stereo analog audio
• Impedance: 33Ω output impedance
• Volume Control: Software-based (alsamixer)
• Use: Headphones, powered speakers (with amplifier)

HDMI Audio:

• Format: PCM, compressed (DTS, Dolby)
• Channels: Up to 8 channels
• Sample Rate: 32 kHz to 192 kHz
• Bit Depth: 16-24 bit

For router applications, both audio outputs are typically unused (headless operation).

Power Delivery

Power Input

5V USB-C Power:

• Connector: USB Type-C
• Voltage: 5.0V nominal (±5%)
• Current: 3.0A typical operating
• Peak Current: Up to 3.5A (with voltage regulation)
• Power Connector: Dedicated 5V input (not data-capable)

Voltage Regulation:

• Primary Regulator: Synchronous buck converter
• Input Filtering: Multiple capacitors for stable supply
• Output Ripple: <50 mV typical
• Short Circuit Protection: Electronic

Power Consumption by State

Idle (Boot, no activity):

• Power: 2.7W
• Primary Drain: GPU rendering, system services
• 24-hour Usage: 65 kWh/year equivalent

Typical Load (Standard Routing):

• Power: 12-15W
• Load Type: Full-speed nftables routing, DNS
• CPU Utilization: 40-60%
• Thermal: 60-70°C with proper cooling

Peak Load (All Features):

• Power: 18-20W
• Load Type: Gigabit routing + VPN + monitoring
• CPU Utilization: 85-95%
• Thermal: 75-80°C with active cooling

Sleep State:

• Power: Not supported (Pi 4 has no low-power sleep mode)
• Workaround: Controlled shutdown/startup via GPIO

Recommended Power Supplies

For 24/7 router operation:

Official Raspberry Pi PSU (Recommended):

• Capacity: 5.1V 3A
• Quality: Premium regulation
• Certified: Meets all specifications
• Cost: ~$20-25

Third-Party Quality PSU:

• Specification: 5V 3A minimum
• Requirements: UL/CE certified, ≤5% regulation
• Rating: Industrial/enterprise preferred for 24/7

Backup Power (Battery):

• Type: UPS with 5V output
• Capacity: 10,000-25,000 mAh recommended
• Runtime: 30 minutes - 2 hours depending on capacity
• Use: Graceful shutdown on power loss

Physical Specifications

Dimensions

• Length: 88.0 mm
• Width: 58.0 mm
• Height: 19.4 mm (including heatspreader)
• Connector Overhang: USB/HDMI add ~5mm
• Total with Case: 90-100mm (case dependent)

Mechanical Features

Mounting:

• Mounting Holes: 4x 2.75mm holes (M2.5 standoffs standard)
• Spacing: 49mm x 49mm (standard Raspberry Pi form factor)
• HAT Compatibility: 40-pin GPIO connector

Connectors:

• USB-C Power: Flush mounted
• Gigabit Ethernet: Full-size RJ45, keyed
• USB 3.0: Type-A, stacked, requires ~15mm clearance
• USB 2.0: Type-A, standard clearance
• microSD: Push-in card slot, under GPIO header
• HDMI: Full-size, right-angle case compatible
• GPIO: 2x20 straight header (or via HAT)

Thermal Management

Heatspreader:

• Material: Aluminum (passive thermal interface)
• Contact Surface: Direct on BCM2711 and LPDDR4 chips
• Effect: Improves passive cooling by ~5-10°C

Thermal Characteristics:

• Idle Junction Temperature: 40-50°C (typical room)
• Operating Range: -40°C to +85°C (rated)
• Throttle Point: 80°C
• Shutdown: 85°C

Cooling Recommendations:

For 24/7 router operation:

• Minimum: Large heatsink + adequate airflow
• Recommended: Active fan cooling (30mm, 5V PWM)
• Optimal: Case with integrated cooler

Revision History

Model Variants by Revision

Rev 1.0 (Launch) - June 2019:

• Initial release
• CPU Clock: 1.5 GHz

Rev 1.1 - Early 2020:

• Unchanged from 1.0 externally
• Internal component changes

Rev 1.2+ - June 2021 onwards:

• CPU Clock Boost: Increased to 1.8 GHz
• Minor power efficiency improvements
• Firmware support required for full 1.8 GHz

Rev 1.3 (Recent):

• Slightly improved thermal management
• Same electrical specifications
• Marginal performance improvements

Compatibility

All RPi 4 revisions are software/firmware compatible:

• Same GPIO layout
• Same connector positions
• Same electrical specifications
• Same OS support

Environmental Specifications

Operating Conditions

Temperature:

• Operating Range: 0°C to +50°C
• Storage Range: -20°C to +70°C
• Thermal Throttling: Begins at 80°C
• Shutdown: At 85°C

Humidity:

• Operating: 0-95% non-condensing
• Storage: 0-95% non-condensing

Altitude:

• Operating: Up to 3000 meters
• Storage: Up to 10,000 meters

Compliance and Standards

• FCC: Part 15 Class B (USA)
• CE: Conforms to EU regulations
• RoHS: Compliant (EU Directive 2011/65/EU)
• REACH: Compliant (EU Regulation (EC) No 1907/2006)
• WEEE: Compliant (EU Directive 2012/19/EU)

Related Documentation

• RPi 4 Hardware Platform - Overview and architecture
• RPi 4 Thermal Management - Cooling solutions
• Hardware Overview - Storage, power, cooling