Docked or undocked? That is the question

Those of you lucky enough to have received your Nintendo Switch today - along with a copy of The Legend of Zelda: Breath of the Wild, no doubt - then you may have already tried the game in both its docked and portable iterations.

Given that the docked mode is supposed to give the console a performance boost, it's perhaps surprising that Digital Foundry has discovered that the game actually runs more smoothly in the Switch's undocked, portable mode. As we noted in our own review, there are moments of stutter when playing on the TV, but nothing game-breaking.

We'll let the tech experts take it from here:

In terms of performance, it's immediately clear to the naked eye that the docked Zelda stutters in places where the mobile experience does not - and to confirm this, we manually counted frames by eye based on our camera shots to ensure accuracy in producing the performance test below. It's really easy to isolate this issue as it occurs frequently in the open world, right from the beginning of the game. In some places, we see the smooth 30fps update while docked drop down to a momentary 20fps - confirming a basic double-buffer v-sync implementation.

What's curious is that the stutter is fleeting, effectively ruling out GPU rendering as the cause - as the on-screen content doesn't change. And that begs the question - if it's a CPU issue, why do we have these issues at all bearing in mind that we know that docked and undocked CPU clock-speeds are identical at 1020MHz? Well, one thing we have to bear in mind is that although there is a big jump in GPU clocks as we move from docked to mobile, there's not a great deal of difference in memory bandwidth between the two modes.

This is only a theory, but it does make sense based on the data available. Laying out the maths here, docking increases pixel count from 720p to 900p, a 56 per cent in resolution. However, memory bandwidth only rises by 20 per cent, from 1331MHz to 1600MHz. Bandwidth is shared between CPU and GPU, so the higher resolution in the home console mode may be sapping memory bandwidth away from the main processor cores, making us more prone to slowdown when the CPU is under load. Bandwidth concerns may also explain why resolution doesn't scale closer in line with the difference in clock-speeds (307.2MHz or 384MHz undocked, 768MHz docked). Suffice to say, if you're looking to play Breath of the Wild with minimal performance drops, running undocked is the way forward.

Digital Foundry asserts that in purely visual terms, the experience is almost identical between docked and undocked, although there are some benefits to be had from running it via the TV:

...playing while docked highlights one visual improvement: texture filtering still isn't great, but it's clearly improved over the handheld version, resolving more ground detail in particular further away from the player. Will you actually notice outside of eyeballing screenshots? It's highly unlikely. Miniaturising the action onto the 6.2-inch screen makes the difference virtually indistinguishable, and the improvement - such as it is - manifests as a 'band' of additional texture detail just ahead of the Link character.

We'd argue the difference is a little more notable between portable and TV in terms of the visual impact, but that's just an opinion!

Given that Breath of the Wild is an early Switch title - and one which began life as a Wii U game, lest we forget - we'd imagine that things will improve as time goes by and Nintendo gets a grip on the hardware. Even so, the moments of stutter when playing docked are miles away from being deal-breaking, and in both docked and portable forms Breath of the Wild represents a stunning technical achievement - what's interesting is that playing docked doesn't offer the performance benefits that many had expected.