Optimizing hybrid laptop performance with Cross Adapter Scan-Out (CASO)

Introduction

For an avid gamer, having a robust Graphics Processing Unit (GPU) is non-negotiable for an optimal gaming experience. Hybrid laptops, equipped with both an integrated GPU (iGPU) and a discrete GPU (dGPU), have become a popular choice for many. If you’ve delved into maximizing your laptop gaming performance, you’ve undoubtedly heard of specialized hardware solutions like NVIDIA’s Advanced Optimus or AMDs Smart Access Graphics.

But what if your laptop lacks these dedicated features? That’s where DirectX’s Cross Adapter Scan-Out (CASO) comes into play. Without the need for specialized hardware solutions, CASO enhances the performance of hybrid laptops that meet the basic hardware and Windows 11 requirements. Keep reading to learn more about how CASO works and how it can benefit you.

Some fundamentals first

Before we dive into the details of CASO, let’s demystify some foundational concepts that set the stage:

• Frames per Second (FPS) is a measure of how many images or frames are displayed on the screen per second while playing a game. The higher the FPS, the smoother and more fluid the game appears to be. Higher FPS makes it easier to control your character and interact with the game world.
• Display Latency is the time delay between when you take an action in a game and when the action appears on your screen. Lower display latency is crucial for a responsive gaming experience because it ensures that your actions feel immediate and synchronized with the game and helps you to react more quickly to in-game events.

Cross Adapter Scan-out (CASO)

On a hybrid laptop, an integrated GPU (iGPU) handles everyday productivity tasks and a discrete GPU (dGPU) or external GPU (eGPU) takes care of the heavy graphics work. Usually, the iGPU is connected to the integrated display and the dGPU/eGPU renders the game visuals and sends them to the iGPU, which then displays them on the screen. This balances the need for performance and power saving by transferring heavy work to the dGPU for performance, while handling the display via the iGPU for power saving. This workflow involves two copies of the rendered frames, one from the dGPU/eGPU to a shared resource and from this shared resource to the iGPU.

But, for gaming sessions that need higher performance, since all rendered visual data has to pass through iGPU for display, we are not getting the full benefit of dGPU performance. To harness the full power of dGPUs, NVIDIA’s Advanced Optimus or AMD’s Smart Access Graphics utilize a multiplexer (mux) solution. A mux solution switches the display connection to dGPU for graphic intensive scenarios like gaming, while keeping the display connection with iGPU for other everyday tasks. When dGPU is directly connected to the integrated display, it performs both the rendering and displaying of visuals on the screen. This avoids data transfer between GPUs and maximizes the dGPUs’ utilization for gaming sessions.

However, not all existing hybrid laptops include a mux solution. In addition, utilizing a dGPU for greater performance comes at the expense of additional power consumption, and hence reduces battery life. CASO streamlines this for hybrid laptops that don’t have a mux solution or don’t have mux enabled. Instead of two copies, CASO requires only a single copy of the rendered visuals which is then directly scanned out to the display. This optimized process results in better FPS and lower display latency, offering a substantial performance boost on hybrid laptops.

For more in-depth technical information on CASO, please visit: Supporting cross-adapter resource scan-out – Windows drivers | Microsoft Learn

CASO Performance

We first released CASO with support for DirectX 11 in 2021 and expanded its reach to DirectX 12 during early 2023, which means that CASO now supports almost all PC games.

In our tests, on a select set of popular PC games, we observed an average of ~16% FPS increase¹ and ~27% display latency reduction¹. In addition, CASO contributed to a 45% decrease in timeout detection and recovery events (TDRs), which means that CASO-enabled laptops are more stable, i.e. suffer fewer crashes and freezes while playing a game.

CASO System requirements

CASO is already integrated into Windows 11 and provides a no-cost performance upgrade on hybrid laptops. CASO has no minimum dGPU requirements and it is enabled by default on supported devices. All you need is a hybrid laptop that meets CASO System Requirements provided below:

More about CASO from our partners

• AMD

“As a testament to our long-standing partnership and commitment to technology innovation, together we made hybrid graphics better for gamers, delivering more frames per second and lower latency. CASO is available starting on AMD Ryzen^TM 6000 Series processors with Radeon^TM graphics, the most advanced processor in its class for high-end gaming on ultrathin notebooks.”

• Intel

“Intel strives to improve gaming performance and CASO delivers such improvements with reduced frame latency and increased FPS with our integrated and dedicated GPU offerings”.

• Nvidia

“All currently supported NVIDIA GeForce GPUs support CASO starting with driver version r515_00. 

The latest GeForce Game Ready Driver is available for download here.”

In summary, CASO provides a valuable, cost-effective performance boost for gamers without the need to invest in dedicated hardware solutions. There are more features in the pipeline that will further enhance the user experience on Windows 11, so please keep tuned to our blog and our discord channel.

1. The performance numbers can vary depending on the hardware, app/game, and app/game configuration used. The numbers mentioned above are based on a sample set of popular games and system configurations.

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