M4 MacBook Air Performance: External Display Test

Here's a question that shouldn't need asking in 2025: Does plugging a modern laptop into an external monitor hurt its performance? The fact that it's still being tested tells you something about where we are with thin-and-light machines trying to be everything to everyone.

Adam from Adam Doing Tech got his hands on the base M4 MacBook Air—16GB RAM, 256GB storage—and decided to find out. His test was straightforward: run Blender rendering benchmarks with and without a 4K monitor connected at 120Hz. The results land somewhere between obvious and interesting, depending on what you expected.

The Setup

The test used a 4K monitor running at 120Hz through an HDMI 2.1 cable, the kind that can push 48Gbps and handle 8K at 60Hz if you're into that sort of thing. The MacBook Air M4 was set to GPU compute mode in Blender, using its 8-core GPU. No CPU rendering, no fancy cooling setups, no high-power mode—because the M4 MacBook Air doesn't have one.

That last bit matters. Apple reserves power modes for its higher-end chips. The M4 Air runs at whatever speed it runs at, period. This isn't a complaint so much as a design choice: Apple decided thermal constraints and battery life matter more than giving users performance toggles. Whether that's the right call depends on your workflow.

The benchmark was the "junk shop" scene in Blender, a standard test that lets you compare results across different hardware. Without an external display, the M4 Air completed the render in 20 seconds. With the 4K monitor connected at 120Hz: 19.79 seconds.

"That's actually faster than you not having the display connected," Adam noted. "So when you have the display connected, you're not going to lose any performance and maybe even the performance is just a little bit better."

A second run came in at 19.59 seconds. Splitting hairs? Probably. But it confirms what should be true: connecting a display doesn't tank performance.

What This Actually Tells Us

The M4 Air isn't struggling to drive a 4K display at 120Hz. That much is clear. Whether the fractional speed improvement is real or noise is harder to say. Rendering benchmarks can vary run to run based on thermal conditions, background processes, and whether Mercury is in retrograde for all the consistency you sometimes get.

What's more interesting is what Adam observed about viewport performance—the real-time responsiveness as you manipulate 3D scenes. "It feels smoother because I am connected to a 120 Hz monitor as well rather than a 60Hz monitor which is usually the one that is coming with the MacBook Air M4," he said. That tracks. Higher refresh rates make interfaces feel more responsive whether you're rotating a 3D model or just scrolling a webpage.

The M4 Air's built-in display runs at 60Hz. Many users won't notice or care. But if you're used to 120Hz or higher, going back feels like wading through gelatin. It's not a performance issue—it's a perception issue that affects how fluid everything feels.

Context From History

For comparison, Adam's previous tests showed the M1 Max completing the same render in 23 seconds, an Nvidia RTX 3070 Ti mobile GPU in 18 seconds, and a desktop RTX 5060 Ti in 13 seconds. The M4 Air at 20 seconds slots in respectably for a fanless laptop that prioritizes portability over raw power.

Apple's M-series chips have been chipping away at the performance gap between mobile and desktop for four generations now. They're not there yet for heavy rendering workloads—desktop GPUs with active cooling and higher power budgets still win. But the gap has narrowed enough that a base-model Air can handle professional 3D work without bursting into flames or requiring a second mortgage for a workstation.

The Missing Variables

What we don't know from this test: battery life impact, thermals over extended rendering sessions, or whether resolution matters. Does driving a 1080p display at 60Hz change anything? What about 5K or 6K? The test looked at one configuration at one moment in time.

We also don't know if cable quality matters as much as suggested. The video heavily emphasizes the high-end HDMI cable used, but the actual signal requirements for 4K at 120Hz are well within HDMI 2.1 spec. A certified cable should work. Whether braided materials and premium construction make a measurable difference is a separate question that the test doesn't address.

What Users Should Consider

If you're buying an M4 MacBook Air planning to use it with an external display for Blender or similar GPU-heavy work, this test says you won't lose performance. That's useful to know. Whether a fanless Air is the right machine for sustained rendering workloads is a different question. You can do it—but you're choosing portability over the thermal headroom that the M4 Pro and Max chips get with active cooling.

The bigger question is whether you need more RAM. The 16GB in the base model is adequate for moderate Blender scenes. Complex projects with high-resolution textures will hit that ceiling faster than you think. Apple charges handsomely for memory upgrades, which is why Adam called out the 256GB storage as something he doesn't recommend. When you're already looking at configuration costs, the base model stops looking like such a deal.

For five decades I've watched this pattern repeat: new hardware arrives, someone tests whether an obvious thing works, and we're all slightly surprised when it does. That we're still checking whether laptops can handle external displays in 2025 says less about the M4 Air than it does about how thoroughly earlier generations of ultra-thin machines burned us with thermal throttling and compromised performance.

The M4 Air apparently didn't get that memo. It just works.

—Bob Reynolds, Senior Technology Correspondent