Hi everyone,
Yesterday, I have completed all the setup guide for eGPU and made it done with all my efforts. Unfortunately, the poor performance made me feel very disappointed so I really want to know the truth (that's limit of eGPU or my configuration had some mistake). The game I build for the test is Pro Evolution Soccer 2019 (even I make all settings to low and change from fullscreen to window screen with the resolution is 1280 x 800 ) but the frame rates are very poor. It's really funny that my dGPU (Radeon r9 m370x ) performance was better than comparing with my eGPU (Radeon RX 580). I'm just feeling like I throw 700$(600$ and 88$ cable) out the window 
I don't have an external monitor so I have to use MacBook internal display. If I buy a new external monitor, fps will be increased much or just a little like 1-2 fps to compare with my internal display.
My Environments are :
- MacBook Pro Mid 2015 (Radeon R9 M370X)
- Sonnet Breakaway 550 (Power Color Radeon RX 580)
- Thunderbolt 3 to 2 cable
- Windows 10 build 1903
By the way, anyone knows some eGPU tool check? I really want to check my eGPU run properly or not (with full power, bandwidth by thunderbolt 2 cable) - I know that its power will reduce a little because I use thunderbolt 2 (instead of thunderbolt 3)
Macbook Pro Mid 2015 (Radeon R9 M370X)
Sonnet Breakaway 550 + Radeon RX 580
The reason you are seeing such poor performance is because you have a 2015 MacBook Pro, which has Thunderbolt 2. Thunderbolt 2 has half the bandwidth of Thunderbolt 3 and is bottle necking your GPU severally, not just a little.
MacBook Pro (13-inch, 2016, Two Thunderbolt 3 ports), Razer Core X, Reference RX 480 4GB
Thanks @drmacintosh
Thanks 4 your reply, could you give me some suggestion about eGPU hardware tool check? I really want to see the bandwidth, data transfer...
Macbook Pro Mid 2015 (Radeon R9 M370X)
Sonnet Breakaway 550 + Radeon RX 580
Are you using MacsFanControl? I've found that on my 2014 i7 15' the fans need to be locked at 100% while gaming or the CPU will eventually throttle and ruin your performance.
Performance will be much better on an external display.
Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts
Thanks @pizzacat
I have MacsFanControl but I'm testing the game on Windows 10 environment. I understand overheat will cause GPU or CPU reduces the performance but I think the main problem is internal display issue exactly. Thanks.
Macbook Pro Mid 2015 (Radeon R9 M370X)
Sonnet Breakaway 550 + Radeon RX 580
I'm talking about the Windows build of MacsFanControl, install it and lock both fans at 100%. Especially if you're running the internal display.
Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts
dear @pizzacat
Thanks so much. I did not know that macsfancontrol has its version on windows. I will let it run 100% everytime i run game ^^
Macbook Pro Mid 2015 (Radeon R9 M370X)
Sonnet Breakaway 550 + Radeon RX 580
It really makes a huge difference too- keep the bottom of the computer as cool as possible. Add cooling until the clock speed doesn't throttle from 3.xGhz and the performance is superb.
Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts