M.2 and SATA III on one PCIe card?

burnthefires

macrumors member
Original poster
May 26, 2017
33
3
I'm hoping for a miracle after digging through the web.
Right now i've got only one PCIe slot left in my 5.1 (others occupied by GPU, RME HDSPe audio interface and Inateck Kt4004 USB 3.0 card).
I'd love to get a bootable SATA III card for my good old crucial mx100 which is running at half it's speed on SATA II, but at the same time i just removed an Apple AHCI SSD(Samsung MZ-JPV1280) from my MBPr and since it's not that easy to sell i decided to put it in my cMP and use it as a system drive.
So here's my dilemma - is there a M.2 PCIe card that also incorporates a SATA III controller? Or should i just get rid of the Inateck card and get a USB3/SATAIII combo card?
 

burnthefires

macrumors member
Original poster
May 26, 2017
33
3
Thanks, it's quite an overkill(can't find the price anywhere but i'm assuming it's not worth my needs here) also it's NVMe and the Apple SSD i'm planning to use is AHCI.
 

h9826790

macrumors G5
Apr 3, 2014
12,800
5,622
Hong Kong
Not sure why you want this setup, just have some sharing.

For OS, there is almost no benefit to run the SSD on a SATA III card. I have this setup at this moment, and I can tell you that the computer's responsiveness feeling identical to SATA II connection. Of course, I can still benefit by having higher sequential speed when copying very large files to/from other hard drives, or (un)ziping files, but that's not quite related to OS ops, and if you have a separated PCIe SSD, you can do all the sequential speed demanding job at there.

The reason behind is that OS mainly need small random read performance, which is not bottlenecked by SATA II connection (a normal SSD only has ~30MB/s 4K random read performance, which is way below the 250MB/s bandwidth that SATA II connection provide).

From this graph, it's very clear that the boot time from SATA II all the way to PCIe x2 is roughly the same.
900x900px-LL-1fb52e74_Screenshot_1.png

The bottleneck is actually inside the SSD, but not the connection.

The cost of getting a PCIe SSD adaptor is low, but the cost of getting a decent speed SATA III PCIe card is relatively high (because of a high quality SATA controller is required). There are some cheaper but low quality SATA III cards, but may only able to provide up to around 350-400MB/s, there is no point to upgrade to this kind of adaptor (and you may have to scarifies some stability as well).

So, since you already have a PCIe SSD on hand. IMO, it's more reasonable to get a low cost adaptor that only can accommodate that PCIe SSD, which allow you to do some demanding job. And let the SATA SSD stay at the native SATA II port to run the OS, which will gives you identical OS performance with SATA III connection with best compatibility and stability.
 
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