@Alienware Area-51 ALX 2006 Not sure where you found that quote, but yes the AGA is essentially just a PCIe x16 slot outside of the system that just happens to have a proprietary cable to connect it to the system. But from a functional perspective, it would be just like having a PCIe x16 slot on a desktop PC. I'm not sure why whatever quote you found talks about SATA and LAN channels when discussing eGPU enclosures, but typical eGPU enclosures use Thunderbolt 3 since that's an industry standard, but TB3 only offers either PCIe x2 or PCIe x4. That doesn't create much of a real world bottleneck, but the AGA nonetheless runs a full PCIe x16 interface.
@SchrodingersRabbits Well you already have real world confirmation from someone else in this thread who's running the setup you're planning, and I'll take real world confirmation over documentation or answers from any tech/sales support rep at any company, since all of those sources have been known to be wrong from time to time, but it's hard to argue with real world results. And while I can understand the reassurance of official confirmation, like I said you're dealing with something that's designed to operate with anything that falls within certain standards, so wanting confirmation about each specific GPU someone might want to run would be somewhat like wanting official confirmation that a given system is compatible with each specific hard drive model or USB peripheral out there that someone might want to use with said system, and that level of confirmation isn't provided. Systems are just said to have SATA/NVMe slots and USB 2.0, 3.0, or Type-C ports, and that's supposed to indicate whether a given device can be expected to work. Of course there's still the potential for strange interoperability problems that occasionally crop up even though they shouldn't exist, but ironically those are the ones that tend to get MISSED in documentation and only discovered by real world testing. But like I said, you already got confirmation in this very thread that someone is running a 1660 Ti in an AGA without any issues, so there's no reason to suspect that a 1660 non-Ti would be an issue.
But hey, you can always order your 1660 from a retailer that offers easy returns. It's not like a GPU would be a huge ordeal to ship back.
Alienware 18 R1 4940MX 4.6GHz, RTX 2080, 32GB DDR3
Alienware 17 R5 i9-8950HK 4.5GHz, GTX 1080 OC, 32GB DDR4 2666MHz
Alienware 15 R1 4710HQ 4.1GHz, GTX 980M, 16GB DDR3
M18x R2 3930MX 4.1GHz, SLI GTX 980M, 16GB DDR3 1600MHz
M17x R5 Core i7-4700MQ 3.7GHz, GTX 980M, 32GB DDR3 1600MHz
My YouTube channel = Area 51 A L X
If my reply solved the issue, please click the, "Accept as Solution" button!