Arm Architecture, SoC Development, and AI Acceleration

1. Introduction to Arm

Arm is a processor design company that creates blueprints (BP) and licenses both its ISA (Instruction Set Architecture) and microarchitecture designs.
👉 Arm Developer

Arm’s CPU architectures are implemented by a wide range of microarchitectures.

Architecture (ISA) defines:
- Basic instruction set
- Exception handling
- Memory model

Arm Profiles

A (Application) Profile: Runs full systems like Linux
R (Real-time) Profile: Runs RTOS or bare-metal code (BMC), for safety-critical systems
M (Microcontroller) Profile: Runs RTOS or BMC, optimized for efficiency

2. Arm Architecture Profiles

A-Profile

Supports both 32-bit and 64-bit execution:

AArch32: T32 + A32 IS (backward compatible with Armv7-A)
AArch64: A64 IS (modern 64-bit execution)

Latest versions (2025):

v9.4-A (in sync with v8.9-A)
Armv9 introduces:
- SVE2 (Scalable Vector Extension 2)
- aSIMD (NEON SIMD)
- Security isolation

🔗 SIMD overview
🔗 SVE2 documentation

Key Milestones

v8.1: AArch64 introduction
v8.2: FP16 support (Half-precision floating point)
v8.3: Improved JS data type conversion
v8.4: Memory partitioning, SHA acceleration
v8.5 / v9.0: Memory tagging, branch target identification
v8.6 / v9.1: GEMM (General Matrix Multiply)
v8.7 / v9.2: PCIe hotplug
v8.8 / v9.3: PAC enhancements, optimized memcpy(), memset()

R-Profile

Designed for time-sensitive and safety-critical systems.
Features:

PMSA & MPU
Functional safety (ISO 26262, IEC 61508 certified from R52+)
SSD/HDD controllers (R82 supports DRAM up to 1TB)
Safety Island for isolation and rapid response

M-Profile

Optimized for microcontrollers and efficiency.

v8-M Baseline: Minimalist, bare-metal
v8-M Mainline: Feature-rich extension
v8-M23: Successor to v6-M
v8-M33: Successor to v7-M

Supports Helium technology (vector extension for ML & DSP).

Cortex-M55, M85 support Helium
Difference vs Neon:
- Helium = designed for small, low-power CPUs
- Optimized for loop prediction, lane prediction, and complex math ops
Lacks a secure monitor

3. Arm System IP

AMBA (Advanced Microcontroller Bus Architecture)

Provides flexible interconnect protocols.

APB: Low-bandwidth control (registers, system peripherals)
AHB: High-speed single-clock edge
AXI-CE: System-wide coherency
CHI: High-performance coherent interconnect
C2C (Chip-to-Chip): Multichip SMP & coherent links

Benefits:

Efficient IP reuse
Flexibility
Compatibility
Ecosystem support

Exception Levels (Armv8 & v9)

EL0: Applications
EL1: OS Kernel
EL2: Hypervisor
EL3: Trusted firmware

Armv9 enhancements:

Memory tagging
Secure EL2
Pointer authentication
Branch target identifier
Crypto extensions

4. SoC Development Flow

Arm’s SoC design flow is similar to other chips:

Frontend
- Define system requirements
- Choose cores, IP, and system-level optimizations
IP Selection & Integration
- Choose pre-verified RTL IP
- Ensure EDA compatibility
Frontend Design & Verification
- RTL design (Verilog)
- Testbenches & constraints validation
Software Development (Parallel)
- Virtual platforms (Arm FVPs)
- Firmware, bootloaders, drivers
- HW/SW co-design
Backend Implementation
- Logic synthesis → gate-level netlist
- Floorplanning, place & route
- Clock tree, parasitic extraction
- STA, DFM, DRC/LVS checks
Tape-out
- GDSII layout to foundry
Validation
- FPGA / validation boards
Mass Production
- Yield optimization

Key Components of Arm SoCs

CPU cores: Cortex-A, R, M
Memory subsystems: caches, SRAM, ROM
AMBA interconnect
System IP & Corstone (prebuilt compute subsystems)
Peripherals: UART, I2C, USB, SPI, GPIOs, timers, ADC/DAC
Accelerators: AI/ML via Ethos NPUs
Security: TrustZone, secure boot, TPM
Power/Clock management: DVFS, gating, power islands

🔗 SoC Labs

5. Arm Ethos-U (NPU)

Arm’s Ethos-U NPUs provide dedicated ML acceleration.

U55: 256 MAC (CNN focus)
U65: 512 MAC
U85: 2048 MAC (Transformer focus)

Workflow

NN ops assigned to NPU
Conditions & post-processing on CPU
Weights in flash, activations in SRAM
CPU triggers execution, handles interrupts

Standards & Software:

TOSA (Tensor Operator Set Architecture) support
CMSIS-NN kernels for Cortex-M fallback
uTFL (TensorFlow Lite Micro) support (INT8 only)
Vela compiler for operator partitioning & quantization
Arm NN: ML framework bridge
KleidiAI: Optimized NN runtime

6. CPU & GPU Optimization

CPU Optimizations

Instruction-level parallelism (pipelines, OoO execution)
Data-level parallelism (SIMD, SME)
Branch prediction & speculative execution
Cache prefetching & tuning
Power efficiency (DVFS, C-states)
Multi-core parallelism

GPU Optimizations

SIMD & SIMT execution
Memory hierarchy optimization
Multi-precision support
MMA units (like tensor cores)

7. Neural Network Optimizations

Quantization (linear + QAT)
Pruning (remove redundant layers)
Knowledge Distillation (teacher/student models)
Matrix optimizations:
- Loop reordering
- Tiling
- Loop unrolling
- Multi-core parallelism (OpenMP, SMT)

Advanced Features

SVE2 + SME (Scalable Matrix Extension)
- Dedicated tile storage (ZA)
- Streaming execution mode

All of these are integrated into KleidiAI libraries.

🔗 Arm University GitHub
🔗 Arm Developer Labs

8. Conclusion

Arm’s ecosystem spans CPU, GPU, and NPU architectures, connected by robust system IP and optimized through software libraries.

From application processors (A-profile) to real-time controllers (R-profile) and ultra-low-power microcontrollers (M-profile), Arm enables scalable solutions across domains such as IoT, AI, cloud, and mobile computing.

The integration of Ethos NPUs, Helium, Neon, SVE2, and SME highlights Arm’s commitment to AI/ML acceleration and energy-efficient computing for the next generation of devices.

Note: (Latest information: 2025 Aug), any further updates from Arm are not get updated here.