Now I know that the RB2011UiAS is a pretty low end device CPU wise with just a single core MIP 74kc CPU running at 600MHz. But it's cheap and functional so a small set-up such as the charity I'm installing it at is okay (and I didn't charge them for installation). Just got to run three computers and public throttled Wi-Fi connected to FTTC @ 70Mbps.

But I've just configured it at home connected to my 250Mbps Virgin Media connection. All Gbps wired. But when I did the ubiquitous speed test, it was struggling to get >160Mbps. Weird I thought because I've got an identical unit at different site that can easily handle the 400MBps wired connection.

Turns out that I was messing about with the touchscreen controls - I've usually left them on defaults. But I'd changed the default to display the stats of the WAN link. That must take a lot of CPU because that's why the speed test was slow. Turn the display off and voila back to full speed.

You live and learn.

You need CPU cycles to play with the touchscreen, on such a slow CPU any extra load will be noticeable.
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I've seen spikes in rb3011 too, I keep all of mine disabled. Waste of resources. You don't stare at the rack all day anyway.

I disable the LCD on all lower-end models.

On CCR devices that support it, I set a timeout for it to disable itself, and simply tap if I need to look at it.

Setting the timeout (to 5 mins) and having to tap is a perfectly workable solution for me. The LCD screen could be removed entirely for most of my installs as it's often hidden in a cupboard.