What actually will happen on Win7 with booting GPT SSD?

Jun 14, 2018
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Hello! I have read some threads about bugs and unwanted "future" troubles with uEFI and GPT booting disc on Win7 x64. Some even recommended using MBR to make things simple. I tried to google out this issue but couldn't find any specific reports of bugs related to Win7 and uEFI. Wondering if anyone have more information or opposed opinion? Thanks!

I upgrade my X230 with a 1 TB MX500 SATA3 today. I choose GPT when using a recovery CD to install Win7. I choose GPT under the impression of "newer and somewhat better". The installation took days and hours but was successful eventually. However, I found the system slower than expected. (e.g. > 30 sec to startup Windows) Benchmark showed inferior results than others but still looks like a SSD data to me. I wonder whether it has to do with my out-of-date laptop or GPT setting.

(Others': https://imgur.com/VYZV6BQ)
(Mine: https://imgur.com/tpEEZGx)