Why is the hdd speed dropping intermittently?

Question

Iron

Good afternoon!
The first computer - Toshiba win7 laptop with HDD Toshiba MQ01ABF050
Everything worked stably (the computer acted as a cash register and except for 1 program did not work with anything). Suddenly, the system began to slow down a lot. Prots, the memory is not loaded. I checked the HDD with the hdtune program and noticed the strongest failures. The reading diagram is stable within 70-80 mb / s, when it suddenly drops to 2 mb / s and sometimes stays there for a long time or throws it up and down. I connect the HDD via a USB controller and the speed is kept stable within 28-32mb/s. Did check several times.
It was necessary that the cash register worked and started looking for another computer and found DELL where win8 is installed and there is the same story but in a smaller percentage. You can work behind the system, but you can see that it slows down. Also hdtune showed high scatter in the chart. I haven't tested it with usb yet.
Both passed the test for bad blocks and both are clean. smart clean.
What could be the problem? Controller on motherboard or hdd controller?

Answer 1

problematic controller on the motherboard, try plugging the disk into another port
if anything, leave the usb connection as a working one, it's cheaper than replacing the motherboard.

Answer 2

It is possible that another system process is starting to intensively read something on the other side of the disk. Or you read a lot of small files. Maybe fragmentation is to blame .. Everything is solved by installing an SSD. But try running O&O Defrag first

Answer 3

This is a problem with all previous generation Toshiba drives. And the fault here is not in the motherboard, but in the hard disk controller, which "hellishly" heats up (sometimes up to 70 C °). But it does not get as hot when connected via USB because the bandwidth of the port itself is much less than that of Serial ATA (SATA)