Report. It's no longer hot or noisy.
TLDR; My Razer Core + 580 arrived today. Looks like this experiment is a keeper. The laptop already ran cool in clamshell mode with the LG 5k solo clamshell (Radeon High Side 5 watts, 1800-2400 RPM) under light load. Now this same almost-silent experience remains while using two more monitors. It's kosher for me as a desktop replacement, after this extra expense.
***
Example test: I can run HD or 4k YouTube video + backupd + VMWare (Boot Camp partition), and after a while the RPM stabilizes to around 3800, which is quite tolerable under untrivial load. I can still obviously max out the fans, but it takes the same effort as running the 16" solo, as a laptop. Without the eGPU, trying this would instantly max the fans.
The rest of the time it's about as good as I hoped for a year or so ago. Regular web browsing, mail etc. happens at 1800 RPM stable.
Sleep mode works as it used to. eGPU goes silent, only the PSU fan keeps spinning. And sometimes the Mac doesn't wake up the next morning. That's how it already was, so I keep it always on.
The 580 comes with a 0 dB mode: fans are completely off when the eGPU isn't under load. They spin on occasionally, but in desktop use not in a significant way to alter the experience.
There are some cons, but also some workarounds.
1) The Razer Core produces some noise of its own, comparable to perhaps 3500 RPM MacBook fan noise level. It's a different kind of sound, but that's the impression. On the desk it can get distracting.
I mitigated this by locating it under the desk. It's literally hanging in there, with two fabric bands. Nothing touching wood to avoid resonant effects. It's called "Safeware Perfect Mounting Kit", sold around Scandinavia. The desk blocks majority of the noise and changes its profile. 31 dB as reported by Apple Watch, in an otherwise absolutely silent room. Totally OK. As a hobby project, I might change the main fan to Noctua NF-A12x25 FLX 120mm sometime in the future.
2) The Ethernet port isn't reliable. It just doesn't work after a while, even with the latest driver. I knew to expect this, so it's a bummer but not a deal-breaker for me. The USB hub works, and that's good enough. I've got a WiFi mesh for networking. If you don't need a USB hub, get the Core X model. I got the Chroma, because it's one less cable to connect the 10 or so USB devices.
3) There's no #3; I'll send an update if I find issues. It's only been a day. Booting into Boot Camp could be trouble, for example.
As an extra benefit, I can direct workloads to the eGPU, which I've done for most graphics-related apps. It seems to help keeping the dGPU at or near 5 watts even when multitasking with all 3 monitors and many apps. It jumps to 10, 15, even 40 watts, but only for a short burst.
All three monitors perform fluently, scrolling and Mission Control rarely drop a frame, even with tons of windows and Spaces. This wasn't the case without the eGPU and 3 monitors, one being a 5k. I've used to the iPad Pro smoothness and appreciate when a docked MacBook gives a similar experience, though not at 120 Hz.
And something that is a benefit for a silent and extremely small minority out there: I now have two GPUs to play Go against. KataGo can calculate the next move on both. "AlphaGo-at-home." For a silent game, I can use the eGPU for that. MacBook fans don't even spin up. The eGPU makes some funny noises though, while it's trying to beat me to the ground.
Configuration:
- Clamshell mode
- LG 5k direct connect
- Razer Core Chroma + AMD 580 direct connect
- Two WQHD monitors connected to the eGPU (might upgrade to 4k's later)
- A whole lot of USB-C and USB devices connected to the monitors and the eGPU (via a hub)
Note: If your single monitor already consumes 20 W in clamshell mode, the eGPU probably doesn't help with that, nor it helps with the lid-open configuration. It appears that some ext monitors can handle 5 W clamshell solo, others take more, and it doesn't depend on the resolution.
This isn't possible. Connecting external display always turn on dGPU
