Valve’s portable Steam Deck hardware may be delayed for a few months, but that hasn’t stopped Valve from discussing many interesting details about the system
a far-reaching livestream with developer focus
Friday. This included a lot of little things about hardware specifications and software interpolation, but also design decisions about how to compensate for hardware and battery performance problems.
AMD’s purpose-built Steam Deck APU, named after the Aerith
Final Fantasy VII
Character, is the heart of the system and was a focus of the presentation. According to AMD, the system is the company’s first mobile chip with a
RDNA2 GPU architecture
, so it should fully support DirectX 12 and the latest Vulkan APIs. It also means that Steam Deck will not only be compatible with the entire Steam library, but many Steam games already
for the specific chip configuration inside, says Valve.
The CPU part of the Aerith chip has four Zen-2 cores that can execute eight threads at 3.5 GHz. The GPU now has eight RDNA2 processing units with 1.6 GHz.
While most Steam games these days get by with just 8 or 12 GB of RAM, Valve said it went with 16 GB LPDDR5 RAM in Steam Deck because “we want to make sure that Steam Deck is not only compatible with today’s games, but can also run games that haven’t even been released yet.” At least 1 GB of this RAM is dedicated to the GPU, but the unified architecture of Steam Deck means that the GPU can access up to 8 GB or even exceed this limit “from game to game” depending on the game. “The RAM’s 128-bit wide bus also allows for 88 Gbit / s total memory bandwidth, or 55 GB / s / TFLOP, which Valve says outperforms some desktop GPUs.
As for storage, Valve said its tests were based on the real load time between the eMMC drives (on low-end Steam Deck models), NVMe SSDs (on high-end models), and the built-in SD. Card readers showed hardly any differences in the real loading time. Despite vastly different bandwidth speeds for each option, the boot times differed by 25 percent or less in Valve’s early tests (although the company said the tests are far from comprehensive at the moment).
Sip the battery
Valve spent a lot of time talking about how the Steam Deck was optimized for battery life, specifically designed to fit into a tiny power range in the 4-15W range. The LPDDR5 RAM is also used here, although there is no lack of energy-saving functions that come into play in low-stress scenarios such as 2D games and idle / sleep modes. That means a hung steam deck should last “hours or even days” without the need to plug it in, Valve said.
However, when plugged in via USB-C, the deck can draw 45W of power, enough to charge at full speed and power a game at the same time. The Steam Deck can also supply connected peripherals with 7.5W of power, enough to power webcams, wired controllers or external storage devices. When it comes to wireless accessories, Bluetooth 5.0 means that Steam Deck can support wireless headphones and “multiple controllers” at the same time. It can also switch Bluetooth low energy Mode for less intensive use cases.
Valve says it wants to make sure its APU is delivering consistent performance rather than relying on “turbo boost” or other modes that can temporarily increase the hardware performance (and power consumption) of laptops and phones. A game on Steam Deck should perform identically for the first ten seconds and after hours of continuous use, Valve said, and game performance on Steam Deck should be consistent whether plugged in, on battery, docked, charged, or downloaded. Even moderately elevated ambient temperatures shouldn’t affect performance, Valve said. However, when it gets too hot outside, the system can throttle battery charge rates, download speeds, and even SSD speeds to keep the GPU as stable as possible.
Since the APU doesn’t have hard limits on its power consumption, games running on Steam Deck should impose a limit of 60 fps (to match the display) or 30 fps (for games that push the GPU) around battery life to obtain. This frame rate limitation also adds to the battery life of the Steam Deck for many games, AMD said. If a game renders a frame faster than the 16.66 milliseconds required for the 60 fps frame rate, the APU immediately switches to the very energy-saving mode until the frame is displayed and then switches back to full power at the next frame to calculate.
Valve says it is working on a global FPS limiter to enforce the 30/60 FPS guidelines for all games that run on the Steam Deck. Developers have access to “extra buttons” to also fine-tune the balance between performance and battery life.
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