[mjg59]

In addition, the linked forum thread includes a user describing how high resolutions break 2.4GHz networks for them, but 5GHz networks work fine. The display driver is stomping on memory responsible for 2.4GHz, but not 5GHz? I'm really not seeing that as the more likely problem here.

[abainbridge]

5GHz WiFi has more bandwidth than 2.4GHz, so typically will involve larger IO buffers in the driver, which could easily be enough to expose a memory scribbler (I imagine there's a bunch of other features that are enabled/disabled by the frequency band switch too). However, I think asdfasgasdgasdg's answer is the correct reason not to suspect a memory scribbler - ie a memory scribbler would cause the driver to crash/fail and the kernel would log a message.

[londons_explore]

Remember the Pi has an odd architecture and all the IO passes through the GPU. The GPU doesn't log human readable messages anywhere. There's a good chance the GPU did log a crash or failure, but only broadcoms engineers can see it.

[abainbridge]

Er, really, wow. I didn't know that. Can you point me at some more info for that? Surely the GPIOs don't go via the GPU.

[londons_explore]

It's a BCM2711, and the datasheet is NDA only - typical Broadcom!

The VideoCore (Broadcoms GPU) is the main processor on the thing, and the cluster of ARM cores that run Linux are more of a coprocessor which can only see some of RAM.

[StavrosK]

But 5 GHz doesn't fail, only 2.4 GHz does.

[wolfgke]

This is exactly abainbridge's point.

[StavrosK]

How do you mean?

> 5GHz WiFi has more bandwidth than 2.4GHz, so typically will involve larger IO buffers in the driver, which could easily be enough to expose a memory scribbler

He's saying 5 GHz will expose the scribbler, and the opposite is happening, only 2.4 GHz fails.

[abainbridge]

@StavrosK Thanks for wading in in my defence, but I had actually mis-understood the situation :-)

Although, if my theory that the IO buffers are different sizes is true, then that could perturb memory layout enough to expose/hide the bug in either direction.

[StavrosK]

Haha, I was actually the attacker in this instance :)

I do agree that the different IO buffers might hide the bug in one instance, but I think this is just plain old RF noise.