My mother board contains SATA-3 ports however some are listed as S-SATA and I-SATA as shown in the manual:

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I have plugged some harddrives in each of these ports and they both work fine. However I want to know the difference between these ports and I'm having trouble finding the difference between PCH and SCU for SATA. My primary concern is if one type of port is faster than another.

Can someone please explain the difference between these SATA types?


1 Answer 1

  • SCU means Storage Control Unit
  • SCUs support SAS drives with HDD enable module installed
  • SCUs do not support Optical Drives
  • There is no practical performance advantage when using SCU

  • Intel PCH supports two types of RAID controllers: AHCI and SCU

  • The thing listed as PCH is the normal AHCI mode.
  • The AHCI controller supports SATA drives and the SCU controller supports both SATA and SAS drives (Exceptions exist, like the SCU controller for PCH C602 that supports SATA only).

What's important to remember is never to put ODDs on SCU. You have to put any Optical Drives on the normal AHCI (the I-SATA).

If you do use ODDs, put them on I-SATA and the hard drives on S-SATA (for a RAID up to 4).

If you do not use ODDs and you use normal SATA hard drives or SATA SSDs, it won't matter. In this case, you will be able to RAID up to 6 drives with the I-SATA and up to 4 with the S-SATA.

Conclusion: no speed difference.

  • I disagree with the "Conclusion: no speed difference."-part. Where is the evidence backing up that statement? I see ~45% lower write performance on the S-SATA ports when compared to the I-SATA ports. This is with Intel DC S3610 SSDs.
    – Erik
    Sep 17, 2020 at 15:48
  • This depends on controller type/brand/performance. I found S-type with higher performance than I-type tested with enterprise 1.92TB SSDs (about 20% difference). I don't remember the exact controller brands but they were totally different brands.
    – Overmind
    Sep 18, 2020 at 5:19
  • For example with Intel C612 on SM X10DRi, the SCU S-SATA seems to have roughly 6Gbps total bandwidth, i.e. you can max out one drive but not all four. The I-SATA on the other hand has at least double that bandwidth. Sep 15, 2023 at 9:16

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