ARM processors have become ubiquitous in mobile devices and embedded systems. Their low power consumption and customized designs for specific tasks have made them the go-to choice for many applications. However, ARM processors also have some drawbacks that should be considered when selecting a processor architecture.
Performance limitations
While ARM processors are very power efficient, they sacrifice ultimate performance in order to achieve this. ARM CPUs have much lower clock speeds compared to x86 processors from Intel and AMD. The fastest ARM-based chips top out at around 3 GHz, while x86 processors can reach over 5 GHz. This results in lower single-threaded performance on ARM. Multithreaded performance can be improved by adding more cores, but there are still limitations compared to high-end x86 chips.
The ARM instruction set is also simpler than x86, lacking some advanced instructions that can boost performance in certain tasks. Overall, ARM processors are not well-suited to tasks that demand raw processing power like 3D rendering, video editing, scientific computing, and gaming. They work well for relatively simple tasks in mobile devices and embedded systems.
Lack of compatibility
Software compatibility is a major issue with ARM processors. Because they use a different instruction set architecture than mainstream x86 chips, ARM processors cannot natively run x86 software. This requires software developers to port and recompile programs specifically for ARM. A lot of software is now available for mobile ARM processors, but there are still gaps compared to x86.
ARM’s reliance on system-on-chip (SoC) designs also hampers compatibility. Many ARM processors are customized chips that integrate CPU cores with graphics, I/O, and other functionality. This means drivers and other software components need to be tailored for each specific ARM device. General purpose operating systems like Windows have trouble supporting the wide variety of ARM SoC hardware.
No high-performance graphics
High-end graphics capabilities are lacking in the ARM ecosystem. ARM’s Mali GPUs cannot match the 3D gaming performance of discrete GPUs from AMD and Nvidia. While mobile ARM processors have integrated graphics sufficient for basic tasks, they do not have the graphics power needed for VR, AR, 3D modeling, gaming, and other graphics-intensive applications.
ARM’s closed licensing model also prevents third party GPUs from being tightly integrated into ARM SoCs. So there is a dichotomy between the CPU and GPU that limits overall performance in ARM-based systems. Top-end graphics still requires pairing an ARM CPU with a discrete GPU, losing power efficiency advantages.
No standardization or consistency
There is much less standardization and consistency among ARM processors compared to the x86 market. With x86, Intel and AMD publish clear CPU specifications that software developers can rely on for compatibility across processors. The core CPU architecture changes slowly over time.
In contrast, ARM only licenses the basic CPU core design to partners. Each vendor like Qualcomm, Samsung, and Apple then customizes the SoC architecture in different ways. There are many different variations of ARM processor implementations. This fragmentation makes developing software and drivers that work consistently on all ARM devices more challenging.
Lack of virtualization support
Virtualization enables running multiple operating systems as virtual machines on the same hardware. This is commonly used in data centers and for container deployments. While ARM has added basic virtualization capabilities with ARM Virtualization Extensions, it still lags behind leading x86 processors in this regard.
For example, ARM lacks the processor Extended Page Tables (EPT) feature for accelerating MMU virtualization in hardware. This can lead to lower performance for virtualized workloads on ARM servers compared to Xeon or EPYC processors. Full virtualization on ARM is still evolving and has not yet caught up to mature x86 implementations.
Immature software ecosystem
Although the software ecosystem for ARM has certainly grown, especially among mobile and embedded operating systems, it remains less mature compared to x86 software. The dominance of x86 in PCs and servers means most enterprise and productivity software is designed primarily for x86, not ARM. This includes databases, analytics tools, development tools, office suites, and more.
While open source software that can be recompiled for ARM is abundant, commercial proprietary software is still playing catch up. This immaturity of the ARM software ecosystem limits the range of applications that can currently leverage ARM processors. It will take time for more server and productivity software to add ARM support.
Limited to low-power designs
ARM processors top out at power consumption levels around 30 to 40 watts for processors designed for PCs and servers. The ARM architecture is inherently more power efficient than x86. But this means ARM is limited to low-power system designs, both mobile and plugged-in. ARM cannot yet scale up to the 100W+ power envelopes required for high-performance computing and desktop systems.
Even ARM server processors lack the cores and resources required for heavy duty computing like AI training or scientific computing. While suitable for smaller workloads like web serving, their low-power nature will keep ARM pigeonholed to certain niches, unable to compete head-on with power-hungry x86 processors.
Expensive licensing and royalties
While ARM touts its licensing model as an advantage, the reality is their per-device licensing fees and royalties add to the cost of manufacturing ARM-based systems. Companies have to pay millions upfront for an ARM architecture license, then 1-2% royalties on each device shipped. This gets built into the price charged to customers.
In contrast, x86 processors from AMD and Intel do not require any per-device licensing. The x86 instruction set is open. Comparable x86 chips can cost less than ARM counterparts after accounting for licensing fees. That cost gets passed on to consumers. So ARM’s proprietary licensing model actually increases costs compared to x86.
Security risks from customization
The high degree of customization with ARM poses potential security risks. Because vendors can modify ARM cores heavily for different SoC implementations, there is a lack of standardization that makes checking for vulnerabilities difficult. Custom logic could introduce new bugs or security flaws not present in the base ARM core design.
The variability across ARM processors also makes it tricky to apply consistent software security updates and patches. There is no single standard ARM architecture to secure like with x86. Highly customized ARM SoCs expand the attack surface and make security more challenging to implement universally.
Uncertainty in the datacenter market
ARM is trying to push into the datacenter server market to compete with Intel Xeon and AMD EPYC processors. But enterprises and cloud providers are wary of adopting new architectures. Since ARM lags behind in areas like virtualization, it remains uncertain if ARM servers can match the performance, compatibility, and reliability expected for critical workloads.
The lack of ARM-native software also creates deployment challenges. Companies would face porting and transition costs migrating to ARM. This makes datacenter providers reluctant to abandon the mature x86 ecosystem. ARM still has an uphill battle to break into the mainstream server industry.
