However, we noticed latency spikes when we pressed F11 and F12, which are the brightness shortcut buttons on the XPS 15 9570. In short, cycling these buttons always causes unacceptably high latency times. We then rolled both machines back to BIOS 1.8.1 and got the same result. Rather than BIOS 1.10.1 introducing this bug, it appears that it had been present previously and remains unfixed.

Interestingly, no other function button causes these latency spikes, nor does adjusting the screen brightness from within Windows. We have reached out to Dell informing them about this issue, but we are still awaiting a response. We have included a short video below to demonstrate the issue, rather than you just having to take our word for it.

Perhaps we have two units affected with the same issue, which could be the case. This seems rather unlikely though, as they exhibit the same symptoms. As it stands, we are still awaiting a fix, if there is one, to these DPC latency issues.

Let us know in the comments what your experiences of BIOS 1.10.1 are and whether you can replicate this issue.