Architectures and Processors

ARM Cortex-M7 Cache and Memory Configuration Impact on Performance The ARM Cortex-M7 is a high-performance processor designed for applications requiring significant computational power, such as digital signal processing (DSP) and real-time audio processing. However, in this case, the Cortex-M7 running at 300 MHz is underperforming compared to a Cortex-M4 running at 168 MHz when executing…

ARM Cortex-M7, Cortex-A9, and ARM926EJ-S Performance Metrics and Optimization Challenges When working with ARM cores such as the Cortex-M7, Cortex-A9, and ARM926EJ-S, understanding their performance metrics is critical for optimizing embedded systems. Key metrics include DMIPS (Dhrystone MIPS), MFLOPS (Million Floating Point Operations Per Second), CPI (Cycles Per Instruction), and cache-related penalties such as branch…

Incorrect Heap Address Assignment in Cortex-M4 Custom Startup Code The issue revolves around the incorrect initialization of the heap memory region in a custom C++ startup code for the ARM Cortex-M4 processor, specifically targeting the STM32F407VGT6 microcontroller. The heap is intended to be located in the Core Coupled Memory (CCM) region starting at address 0x10000000,…

ARM Cortex-A53 STP Instruction Memory Corruption on AHB Bus The ARM Cortex-A53 processor, a widely used 64-bit core in embedded systems, is known for its efficiency and performance. However, subtle issues can arise when executing certain instructions under specific conditions. One such issue involves the STP (Store Pair) instruction, which is designed to store two…

Cortex-M0 Boot Behavior and Fixed Reset Vector at 0x0000_0000 The ARM Cortex-M0 processor, like other Cortex-M series processors, is designed to start execution from a fixed reset vector located at address 0x0000_0000. This behavior is hardwired into the processor’s design and cannot be changed through software configuration alone. Upon reset, the Cortex-M0 fetches the initial…

Stack Misalignment Leading to Hard Fault on Interrupt Return When working with the ARM Cortex-M4 processor, such as the one found in the STM32 F407 microcontroller, handling interrupts correctly is crucial for stable system operation. One common issue that arises during interrupt handling is improper stack alignment, which can lead to a hard fault when…

SVC Pendability and Exception Entry Behavior in ARM Cortex-M The SuperVisor Call (SVC) exception in ARM Cortex-M processors is a critical mechanism for implementing system calls and transitioning between privilege levels. However, its behavior during exception entry and handling can be nuanced, particularly when higher-priority interrupts preempt the SVC exception. The ARMv7-M architecture defines specific…

ARM Trusted Firmware Boot Process and Cortex-A57 Workarounds The issue revolves around the failure to boot ARM Trusted Firmware (ATF) on a QEMU virtual machine emulating a Cortex-A57 processor. The user is attempting to run bare-metal firmware at Exception Level 2 (EL2) using ATF to manage multi-core bootstrapping via the Power State Coordination Interface (PSCI)….

SMC Call Misrouting to Sync Exception at NS.EL1 Instead of EL3 When working with ARM Cortex-A53 processors, particularly in systems requiring secure and non-secure world transitions, a common issue arises when Secure Monitor Calls (SMC) fail to trap to Exception Level 3 (EL3) as expected. Instead, the processor remains in Non-Secure EL1 and triggers a…

Cortex-M7 VFMA Instruction Pipeline Behavior and Performance Degradation The Cortex-M7’s VFMA (Vector Fused Multiply-Add) instruction is a powerful floating-point operation that combines multiplication and addition in a single cycle, theoretically improving performance for computationally intensive tasks such as polynomial evaluation. However, the observed behavior in the provided benchmarks reveals significant pipeline stalls and performance degradation…