I just bought two new SSDs, the Samsung 850 EVO and HyperX Fury. Testing it in my laptop with SATA III I get the expected transfer rate of 400-500 MB/s.

However, in my SATA II desktop both drives max out at around 210 ! MB/s. From what I read, under SATA II, the drives including overhead should be performing around 285-300 MB/s, so that's 35-40% below what it should, which is a huge loss. Anyone know what could be the reason?

System is Gigabyte GA-P55-UD3R core i3-560,8 Gb RAM, Win 10


UPDATE: just checked with an older SATA II system P35 chipset, Windows 7, and the same SSD is giving much better results (260 write and 230 read)! so is this a Win 10 issue or an AHCI issue perhaps? Weird

  • Under SATA-II real life performance (not theoretical max) seems to top off at 270MB/sec. (And that was with the highest performing chipset). That does still not explain 210 MB./sec serial, but the gap is less than you expect. – Hennes Jul 4 '16 at 16:36
  • What tests were being performed that gave that speed? Reads? Writes? Sequential? Block size? Also, 210/300 = 70%, so I'm not sure where you're getting these 35-40% numbers from? – Ƭᴇcʜιᴇ007 Jul 4 '16 at 16:46
  • I ran ATTO disk benchmark with default settings (Direct I/O-Overlapped I/O) and all the results from 128Kb up to 64Mb seem to max out at around 210 for write and 200 for read on both drives. Interestingly on both the read is always less than the write. 300/210 = 1.43 i.e. 43% faster. – user576053 Jul 4 '16 at 16:52
  • Just checked the same drive in an older system running windows 7, intel P35 chipset and no AHCI, and getting much better results! Writes are around 260 and reads around 230! So what's going on here is this a Windows 10 issue or is it an AHCI issue? It can't be the chipset. – user576053 Jul 4 '16 at 17:17
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    This SATA II desktop, what make/model is the motherboard? And are you sure AHCI is enabled (and if so, is the AHCI driver stock Microsoft or Intel/AMD?) – misha256 Jul 4 '16 at 18:43

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