[SOLVED] Slow Kingston A400 write/read speeds

[calitroppings]

Just bought a brand new Kingston A400 SSD a few hours ago and checked its speeds. Terrible at 260 read and around 150 write. Is this normal?
Something to note is that my MOBO is SATA2 only, and have read that SATA2 only has 3Gb/s which caps the SSD at around 300Mb/s.

 

[rgd1101]

on sata2, you are getting about 50% of what sata3 can offer.
so it sound about right.

SATA2 only has 3Gb/s

on paper.

 

[Maxxify]

SATA2 = 3 Gbps before encoding and I/O or transport overhead. SATA uses 8b/10b encoding so this takes it down to (3)(.8) = 2.4 Gbps. Overhead after that is about 10%, so (2.4)(.9) = 2.16 Gbps. Convert to MB/s, ((2.16/8))(1024) = 276.48 MB/s. Write speed has more overhead so will typically be a bit lower, additionally write speed is dependent on the capacity of the drive and its SLC caching (lower capacity is slower, TLC mode is slower than SLC). So 260 MB/s or so for read is within reason, the write speed might be the base TLC speed.

 

[calitroppings]

SATA2 = 3 Gbps before encoding and I/O or transport overhead. SATA uses 8b/10b encoding so this takes it down to (3)(.8) = 2.4 Gbps. Overhead after that is about 10%, so (2.4)(.9) = 2.16 Gbps. Convert to MB/s, ((2.16/8))(1024) = 276.48 MB/s. Write speed has more overhead so will typically be a bit lower, additionally write speed is dependent on the capacity of the drive and its SLC caching (lower capacity is slower, TLC mode is lower than SLC).

Thank you, I didn't exactly know why it ran at 260MB/s when SATA2 supports 3Gb/s but now I know.

 

[Maxxify]

Thank you, I didn't exactly know why it ran at 260MB/s when SATA2 supports 3Gb/s but now I know.

Yes, fun fact is that there's encoding for everything. PCIe 2.0 is 8b/10b while 3.0/4.0 is 128b/130b. Older USB is 8b/10b while newer is 128b/132b. Transport or I/O overhead is more difficult to quantize, however it's usually about 10%, this is a factor of latency among other things.