Question Question regarding PCIe SATA controller card speed

[Jerethi]

I have a Gigabyte B360 HD3 motherboard, with 6 PCIe slots conforming to the PCIe version 3.0 spec. I recently installed a SATA controller on one of the open PCIe x1 slots. Unfortunately, I'm a little confused over how to read the various PCIe speed and throughput specifications and how that translates to the speeds I should expect from the SATA controller card I just installed.

According to the specs for the SATA controller, it conforms to PCIe version 2.0, and supports SATA3 transfer speeds. However, if I'm reading the PCIe version 3.0 specs correctly, if I'm plugged into a PCIe x1 slot, the maximum throughput I'll get is 984MB/s, which is decidedly less than SATA3 transfer speeds.

I feel like I'm missing a step here somewhere. Can someone point out the error of my was?

Many thanks.

 

[zir_blazer]

SATA 3 is up to 600 MB p/s per link. Each PCIe 2.0 lane gives 500 MB p/s. Basically, a single, fast SSD could theorically saturate the PCIe uplink.

 

[Jerethi]

Thanks for the clarification. Also, your answer helped me realize that I was asking a dumb question to begin with. SATA3's 6.0Gb/s transfer speed equates to about 750MB/s, which is well within the PCIe version 3.0 spec for a single lane.

 

[zir_blazer]

Thanks for the clarification. Also, your answer helped me realize that I was asking a dumb question to begin with. SATA3's 6.0Gb/s transfer speed equates to about 750MB/s, which is well within the PCIe version 3.0 spec for a single lane.

SATA is 600 MB p/s. It is 750 MB p/s raw between the SATA drive and the controller but uses a 8b/10b encoding, so it is 600 MB p/s effective.
And if your PCIe SATA Controller is PCIe 2.0, then it doesn't matters that your Motherboard is 3.0 because it will cap out at 2.0 speeds anyways.

 

[Insert_Nickname]

I recently installed a SATA controller on one of the open PCIe x1 slots. Unfortunately, I'm a little confused over how to read the various PCIe speed and throughput specifications and how that translates to the speeds I should expect from the SATA controller card I just installed.

Most PCIe 2.0 x1 SATA controllers top out at about 375MB/s. PCIe is the bottleneck in this case, as a single lane of PCIe 2.0 can only transfer 500MB/s, which after encoding and bus overhead lands in that ballpark. Of course, this only really matters if you're adding an SSD. Even a couple of HDDs will have plenty of bandwidth with a PCIe 2.0 x1 connection.

Since your chipset supports PCIe 3.0 (Intel Skylake+ platform or AMD X570/B550 chipsets) try to find a card with the JMicron JMB582 chipset. That should get you pretty close to SATA's theoretical limit with a single drive.

 

[Jerethi]

Most PCIe 2.0 x1 SATA controllers top out at about 375MB/s. PCIe is the bottleneck in this case, as a single lane of PCIe 2.0 can only transfer 500MB/s, which after encoding and bus overhead lands in that ballpark. Of course, this only really matters if you're adding an SSD. Even a couple of HDDs will have plenty of bandwidth with a PCIe 2.0 x1 connection.

Since your chipset supports PCIe 3.0 (Intel Skylake+ platform or AMD X570/B550 chipsets) try to find a card with the JMicron JMB582 chipset. That should get you pretty close to SATA's theoretical limit with a single drive.

Extremely informative. Thanks so much.