The Evolution of Power Monitoring in PC Hardware: Extending ACPI SMART, VESA, and I2C for Enhanced Reporting
The evolution of power monitoring in PC hardware has been a slow and fragmented process, hindered by cost-cutting measures and a lack of standardization. Power supplies, the heartbeat of all electronic devices, are often one of the first components to be subjected to cost reduction strategies, as they are typically not seen as providing significant value by the end user.
Current Challenges in Power Monitoring
While some high-end power supplies do offer intense monitoring of rail voltages and consumption, there is a notable lack of agreement on how to share this data. The challenge arises from the fact that monitoring ends up being in-band to the unit under test. In the event of a power supply failure, the PC with substandard power might not be able to reliably report the power issues, as it would rely on the very system that is potentially failing.
The solution would require a small computer within the power supply itself to collect and save the data, but this introduces new challenges such as providing a power source for the internal computer and ensuring device longevity. However, these solutions would likely incur additional costs, making them non-viable for most manufacturers.
The Ideal Architecture of ATX Power Monitoring
The ideal architecture of ATX power monitoring is not currently standardized. This lack of standardization makes it unclear how one would go about building an API that integrates seamlessly with existing systems. Companies like Corsair have made some strides with their Corsair Link technology, but it remains a niche solution, with limited adoption.
Despite the limited demand for detailed PC power monitoring, several systems and components do have the capability to report exact power usage. However, this information is seldom necessary unless a system is built incorrectly or is not properly powered. In such cases, random glitches, power loss, or failure to power on might occur.
Understanding Power Supply Monitoring Capabilities
Power supplies equipped with the capability to report power usage are rare. Instead, measuring power usage at the wall is a more accurate, simpler, and cheaper method. Devices like the Kill-a-Watt provide a straightforward way to monitor power consumption without the complexity and cost of internal component modifications.
Evolution of Standards: VESA, SMART, and I2C
Standards such as VESA, SMART, and I2C have evolved over time. VESA, a standards-making body, continues to be relevant. The SMART standard, originating from Compaq, has been revised for SSDs and is useful in alerting about half of failures pre-failure. However, its effectiveness is determined by the attentiveness of those monitoring the alerts.
Many PC and board manufacturers had buggy ACPI (Advanced Configuration and Power Interface) implementations, which, while they improved over time, paled in comparison to the more flexible device tree implementations used in ARM devices. At a hardware level, different integrated chips are typically connected to an I2C bus, which uses one of six common JTAG dialects or numerous OEM variants. This can create a complex and fragmented ecosystem for power monitoring.
The IEEE 1149.1 JTAG standard is evolving, with the most recent version being from 2022. However, partial implementations are both allowed and common. The IEEE 1149.7 standard offers some power management but is rather limited when it comes to power monitoring over typical I2C. When the I2C bus is used for systems management, it is often referred to as the SMBus (System Management Bus). This bus is commonly used for reading temperatures and spinning up fans in response to system conditions.
Motivations and Barriers to Progress
The motivation for improving power monitoring in PCs is limited, with the typical annual savings for systems with aggressive power management set at around 15%. Hence, there is less incentive for manufacturers to invest in advanced power monitoring technologies.
From a hardware perspective, power monitoring is often not included as a feature in ICs. However, I2C power monitoring ICs do exist and could potentially be added. However, the cost and complexity of such additions might outweigh the benefits.
Software considerations further limit progress. Microsoft is contemplating disabling and removing Windows Management Instrumentation (WMI) to reduce "Living off the Land" attacks, having largely dropped SNMP (Simple Network Management Protocol). Apple has also dropped SNMP from many of their devices. These actions reflect broader security and privacy concerns rather than a direct push towards more advanced power monitoring.
Sadly, it is likely that legislation and conformance to standards such as those required for the CE mark will drive progress. However, entities like Apple often delay progress due to their own internal priorities and timelines.