So after doing some testing with the Zephyrus G14 BIOS update 310 (2023 model), I realized something unfortunate, that Asus completely butchered the silent mode on this laptop that I absolutely loved. Literally one of my favorite parts about this laptop, just gone. I personally couldn't find a difference between BIOS 309 and 310, as both actually exhibited the same behavior with the Silent mode, so TL;DR: Downgrade to BIOS 306 for a great performing silent mode. Disable CPU boost for an even better silent mode. Stay on 309 or 310 for a gimped silent mode. For more info, read on:

Bios 306 and 310 Time Spy Results: https://imgur.com/a/32afjJ3

So we're not talking a small downgrade here. I'm talking less than half the performance in Silent mode at around the same fan noise. Great job Asus. This is just such a huge overcompensation on their part to what was essentially a non-issue. On my 4090 model I could get about 13-14k graphics score in Time Spy (incredible btw) in Silent mode on BIOS 306, but now it's a very sluggish 4-6k. To put that 13-14k in perspective, the G14's Silent mode is about equal to the much heavier and chunkier Lenovo Legion Pro 7i's Balanced mode (which is loud af for some reason) at like half the fan volume. Now it's not too much better than just the iGPU.

What changed? So it seems that they lowered the GPU throttle level to 70C (It will hit this much quicker on the 4080 since it's a smaller die). I tried to use G-Helper to get around this but unfortunately the bios update bakes it in. And it throttles HARD. From 85w to 55w but it's almost like it puts an fps limit in place (I checked for Whisper Mode and even tried uninstalling AC to make sure, but there didn't seem to be an fps limit in place), resulting in Time Spy going from 100 fps to like 34 fps throughout the run. On Bios 306, it only lightly throttles around 75-80C and only down to about 70-75w but still maintains great performance. However, and I think this is the behavior they were trying to stop is that it will do a pretty big frame drop every now and then. But the workaround is so easy. If you disable cpu boost in silent mode, the random frame drops are gone. You get even better performance as the GPU is able to run much more stable with better thermal headroom. Disabling boost is also super easy now thanks to G-Helper and even with boost disabled the CPU scores over 10k in Time Spy and around 14-15k in Cinebench multi-core. If Asus had just spent some time tuning it better rather than overcompensating by just destroying all GPU performance in this mode, then maybe they could've provided an actual decent bios update that would just lightly lower Silent performance when necessary.

Another difference with 310, maybe also 309, is the Silent mode fan curve is actually more aggressive now too. I only opened two tabs in Edge and the fans kicked in. Tested it a few times and every time it only took very few actions before fans would turn on in Silent mode, which is quite the opposite of normal Asus ROG laptop behavior. After downgrading to 306, it now took about 12 tabs, playing some videos, running updates, opening and closing Armoury Crate and MyAsus before fans even kicked in a little bit and then quickly went back down to 0 rpm. Like come on. That's the good stuff that we like Asus, why would you ruin that, lol.

So for now I'd recommend using Asus EZ Flash to downgrade your BIOS to 306 if you weren't having issues with that one. It's very easy to downgrade the BIOS, but you will have to disable Asus' update service (likely already done if you use G-Helper and ran the debloat script) to prevent it from auto-installing the new one when you reboot again. Super annoying that it does that.