62 DIMMs: Dual In‐Line Memory
incentives to add energy-consuming features for sake of compliance, potentially reversing some energy savings. It is also important that sufficient energy be allowed for these features to avoid a decrease in efficacy in computers with increased functionality.
Discrete Graphics Cards
Staff investigated the relationship between graphic cards and system energy consumption. In the initial draft, adders for graphics were not provided, as basic graphics are part of the
baseline assumption and advanced graphics are not needed in idle modes. While the rationale is still mostly valid, some systems do not have integrated graphics solutions and, when a graphic card is provided, it is likely that the display will be connected through it, rather than use an integrated solution. This requires such cards to be in a higher level of operation in idle modes.
When considering incorporating graphic card adders to account for correspondingly higher and necessary functionality, staff considered ENERGY STAR 6.1 and European Union adder levels and schemes. Staff has found that these levels were too high compared to modern graphic card idle performance and even worse when future improvements are considered. Staff held a series of meetings with the IOUs, NRDC, ITI, and the largest two graphic card design companies, NVIDIA and AMD, and discussed levels that would be appropriately adjusted from existing frameworks and would incorporate future improvements. The results of these technical discussions are adders that are significantly more stringent than in existing standards, which represent significant technological progress.
Integrated Display
Adders for integrated displays were included in the 2015 proposal. At that time, the adders were aligned with ENERGY STAR Version 6.1. As discussed in the display section of this report, display efficiency has significantly advanced since the inception of adders in 2012 and was based on computers manufactured before that date. To adjust for improvements in technology, this draft staff report proposes to reduce the adder by 20 percent, consistent with efficiency proposals for stand-alone displays presented later in this report.
Random Access Memory
Adders were proposed in the initial draft for random access memory (RAM) that were aligned with ENERGY STAR Version 6.1. This adder scaled by the size of the memory added, giving 0.8 kWh/year per GB incorporated. Further investigation of the contribution of RAM to energy consumption suggests that consumption is connected with the type of RAM and number of physical modules rather than the size of the memory space in idle mode. The Energy
Commission proposes to change the adder to 2.5 kWh/year per module. This level is based on observed power consumption levels of DDR3 memory in idle across several sizes and on assumption of 75 percent conversion efficiency.
In addition to properly scaling allowances, the proposal to move to a per-module adder addresses the deterioration of the stringency of the standard over time from the expansion of average memory capacity over time. The Commission is interested in additional feedback on
whether to continue to scale memory by capacity, or by number of modules, and if the change is made, what levels to set per module.
Additional Hard Disks
Adders were proposed in the initial draft for hard disks that are aligned with ENERGY STAR 6.1.
This level is appropriate for a typical 3.5-inch hard-disk drive if it is spinning in both short-idle and long-idle modes. However, it is excessive for smaller form-factor hard-disk drives and particularly excessive for solid-state drives. Introducing different adders for different hard-drive parts would require the identification of the primary hard-disk hard-drive versus the secondary drive as it could have implications to the allowable maximum energy use. The primary hard-disk drive is the hard-hard-disk drive used to boot the computer.
Energy-Efficient Ethernet
The Commission-proposed adder for Energy-Efficient Ethernet was taken from the ENERGY STAR Version 6.1 specification. This adder was presented as a calculation to be consistent with ENERGY STAR. The calculation does not contain any variables and could be collapsed into a single number.
8.76 0.2 0.15 0.35 0.876
To further simplify the adder, the Commission proposes a 0.9-kWh-per-year standard for Energy-Efficient Ethernet. Both of these changes will reduce the potential for error and complexity of certification.
Expandability Adder
The workshop on the 2015 staff report, follow-up meetings, and comments from the computer industry emphasized the need to provide a larger allowance for more powerful computers.
ENERGY STAR 6.1 achieves this is with a “p-score” that is equivalent to the rated maximum clock speed of the processor multiplied by the number of cores. Staff analyzed this score as the basis for differentiating energy consumption targets and found that it did not form a good basis for future regulations. This is because a processor varies only slightly in idle power regardless of clock frequency and cores when holding the rest of the hardware constant.
Additional factors that drive idle power consumption were raised through stakeholder
interaction. The first, power supply sizing, is driven by the expandability of a system through interface ports. The larger a power supply is, the larger the power overhead of the related components. Also, the idle mode will be on a lower point in the power supply load curve, which typically leads to diminished conversion efficiency.
The second is the idle mode power draw by an increased number of communication controllers for those interface ports, such as additional USB and Peripheral Component Interconnect (PCI) controllers. Each controller has a power draw in idle as it awaits connection to a device, awaits a wake-up signal, or conducts minor status and maintenance communications.
Stakeholders also raised increasing bandwidth as a driver of idle mode power. Bandwidth is partially solved by frequency scaling in both desktop and notebook computers. It is also related
to the type of interfaces in the motherboard. Staff considered various bus bandwidths as an adjustment for power consumption but ultimately could not find a practical way to identify this information in off-the-shelf products. While motherboard manufacturers publish some of these numbers for do-it-yourself motherboards, desktop and notebook systems typically do not.
To adjust for the effects of expandability, staff proposes to calculate an expandability score, which emulates power supply sizing. This approach appears in industry, IOU, and NRDC proposals and is calculated by the number of ports available in a computer. The higher the score, the more energy a computer can use. The first 200 watts of power are considered typical of a standard system. Subsequent scores accumulate an energy adjustment that increases the allowable energy consumption for compliance. At 750 watts, a desktop must comply with workstation rather than the desktop requirements.
Notebook Computers
The technical feasibility and efficiency opportunities for notebooks are similar to those of desktops. The frequency and extent to which these features and approaches have been
incorporated into notebooks are far greater than in desktops. More than half of the notebooks certified to the ENERGY STAR Version 5 specification already meet the staff proposed notebook standard. In addition, more than 72 percent of models certified to the ENERGY STAR Version 6 specification meet proposed levels as of November 5, 2014. New adders for graphics
accelerators are consistent with the discrete graphics card section above and are reflected in the proposed regulations in Chapter 8. The expandability adder does not apply to notebooks, which characteristically have limited expandability, resulting in a smaller range of power supplies.