Hello. I faced similar issue with Adata SU750 and this is the closest reference of the case that I found on the net. So I want to share my findings here in case other people are having similar issue with their Adata SSD and came here like me.
At first I noticed that my Adata SU750 512GB might be faulty because multiple temp softwares reported that the temp is around 60 celsius and the sequential read and write were only around 200MB/s and 300MB/s respectively. Online searching said that the normal temp is not far above 40 celsius, with read and write speed both above 500MB/s, as officially mentioned in Adata site. I would have returned the SSD if it were not for the fact that it was Sunday and the shop was closed. So what I did was trying some stuff, just in case.
Long story short, it turned out that the SSD need AHCI mode in order to perform as advertised, it is located in the motherboard bios, in sata mode setting. And my Windows 7 was not installed in AHCI mode, so there were 2 registries that I need to change to activate AHCI driver. The Windows will crash if it doesn't activate AHCI driver while the bios setting is on AHCI mode. After I successfully activate the AHCI mode, the read and write speed become normal, both above 500MB/s as advertised.
Now about the temp, I use a WD HDD that runs at 42 celsius side by side with the SSD. It is very warm to the touch, the heat is VERY noticeable, so I assumed 60 celsius SSD would be like blazing hot in comparison, with smaller area to dissipate heat than HDD. But it wasn't. I turned my PC off and I was to take the disks out when I noticed that my HDD was still very warm and the SSD wasn't hot at all. It was not even close the the warmness of the HDD, which is supposedly 20 celsius cooler than the SSD based on the temp softwares. I put the SSD on the floor and turned on the PC, I touch it, top and bottom, as the softwares reported 60-68 celsius: I can't feel any heat. So I think the temperature sensor are reporting the temp inaccurately and there's no real heat issue. I assume they design SSD with heat dissipation in mind, seems unlikely that they want to and can insulate 60 celsius heat in 7 mm thick SSD that well. It is like just room temp, barely noticeably, maybe 30 celsius.
As of now, the read and write speed are as advertised and the temp issue seems only be caused by temp sensor being innacurate so I don't plan to return it. Just minor issue that doesn't really disrupt functionality.
TLDR, if you have similar issue (slower read-write speed than advertised and high temp), make sure your sata is set to AHCI mode in bios and check the physical device if there is actual heat issue (touch the device/thermometer), could be just the sensor not reporting temperature accurately. And make sure you plug the SSD to a sata6 slot on the motherboard, because sata3 caps at 300MB/s and the read/write result will be below that.
Links:
https://www.diffen.com/difference/AHCI_vs_IDE (there is info on how to activate AHCI)
https://www.tomshardware.com/reviews/ssd-upgrade-sata-3gbps,3469-4.html (sata6 vs sata3 sequential read/write speed)
