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eyeangle

macrumors regular
Original poster
Jan 2, 2014
152
19
Melbourne, Australia
Hey guys,

I'm thinking about upgrading my 1TB SSD Sata drive that's sitting on an Apricorn Velocity Solo x2 to an 2TB NVMe SSD for my Mac Pro 5,1.

I'm a simple man and just want JBOD. So I only want one NVMe SSD on the adapter, I don't want two or even four as I'm only going to be using it as my boot drive and the other drive bays are full.

My question is; is there a speed increase from a single NVMe SSD on a x4 PCIe adapter, compared to a single NVMe on a x16 PCIe adapter?

For example, this:

Compared to this:

I'm going to be getting the 970 NVMe M.2 2TB SSD from Samsung. Will I get the full Read speeds of 3500MB/s and write speeds of 2700MB/s if it's sitting on a x4 PCIe card?
 

tsialex

macrumors G4
Jun 13, 2016
10,869
11,358
The M.2 connector is a miniaturised x4 PCIe slot. All M.2 devices are x4 or less lanes PCIe devices.

Don't matter if the adapter PCB physically fits a x4/x8/x16 slot, the M.2 is and always will be x4 - or less lanes, since there are older M.2 devices that are just x2.
 
Last edited:

tsialex

macrumors G4
Jun 13, 2016
10,869
11,358
x8 or x16 will only matter with PCIe switched, cards that have a PCIe switch, adapters. With a PCIe switched NVMe adapter, the switch can convert the MP5,1 PCIe v2.0 x8/x16 slot into PCIe v3.0 x4 internally:

  • With a plain dumb adapter, you are limited to x4 PCIe v2.0, real world ~1450MB/s.
  • With a x8 PCIe switched adapter you are limited to x8 PCIe v2.0 that the switch convert internally to PCIe v3.0 x4, real world ~2950MB/s.
  • With a x16 PCIe switched adapter you are limited to x16 PCIe v2.0 that the switch convert internally to PCIe v3.0 x4, real world ~3200MB/s for one blade and ~6200MB/s for two or more blades.

PCIe switched cards start at around US$ 190 for IO Crest IO-PCE2824-TM2 (aka Syba SI-PEX40129), the most used by MP5,1 owners that want high performance is HighPoint SSD7101A-1, at around US$ 350~400 price point.

Please read the first post of the stickie below:

 
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LFO8

macrumors regular
Apr 27, 2019
189
87
I actually have an issue after installing a

Samsung 970 EVO 1 TB M.2 NVMe​


I popped it into my bottom PCIe slot as it was the only one still free (the other ones are populated by a USB card and my RX580). But the disk speeds I am getting from Black Magic's Disk speed tester can't be right:

Screenshot 2020-11-28 at 12.50.47.png


I am running Mojave with boot ROM 144.0.0.0.0 and this is the PCIe adapter I have placed the NVMe in:

8F359A10-2767-4057-976C-DBD2895FF5C5.jpeg

Does anyone have an idea what might be going wrong here?
 
Last edited:

LFO8

macrumors regular
Apr 27, 2019
189
87
That seems to be an x1 adapter. You should buy an x4 adapter.
Oh.. yes that makes sense. I can’t believe I didn’t realize it was an x1 o_O

so this one should do the trick then:

ABFCA531-A3BB-4EA2-9C4C-9A68E1B21638.jpeg


Edit: I went ahead and ordered this one:

4ABE8168-D314-4766-A569-18FF1DEA6E02.jpeg

Should do the trick nicely plus added bonus of passive cooling. I have noticed the NVMe get’s quite warm during operations. Around 49C
 
Last edited:

mikas

macrumors 6502a
Sep 14, 2017
781
515
Finland
Probably yes.
I have no experience about those. They are dumb adapters so they should work ok, if they are not broken somehow. I have bought some adapters too, like Angelbird, AquaComputer Kryo and a dual slot IOCrest w/PCIe switch, and a couple of cheapos too, like the names you bring up there. They all have worked ok. Cooling is necessary if you stress the NVMe memory strongly. At idle or with moderate usage they seem not to generate any considerable heat to worry about.
 

Popyacap

macrumors newbie
May 22, 2022
3
0
x8 or x16 will only matter with PCIe switched, cards that have a PCIe switch, adapters. With a PCIe switched NVMe adapter, the switch can convert the MP5,1 PCIe v2.0 x8/x16 slot into PCIe v3.0 x4 internally:

  • With a plain dumb adapter, you are limited to x4 PCIe v2.0, real world ~1450MB/s.
  • With a x8 PCIe switched adapter you are limited to x8 PCIe v2.0 that the switch convert internally to PCIe v3.0 x4, real world ~2950MB/s.
  • With a x16 PCIe switched adapter you are limited to x16 PCIe v2.0 that the switch convert internally to PCIe v3.0 x4, real world ~3200MB/s for one blade and ~6200MB/s for two or more blades.

PCIe switched cards start at around US$ 190 for IO Crest IO-PCE2824-TM2 (aka Syba SI-PEX40129), the most used by MP5,1 owners that want high performance is HighPoint SSD7101A-1, at around US$ 350~400 price point.

Please read the first post of the stickie below:

 

Popyacap

macrumors newbie
May 22, 2022
3
0
x8 or x16 will only matter with PCIe switched, cards that have a PCIe switch, adapters. With a PCIe switched NVMe adapter, the switch can convert the MP5,1 PCIe v2.0 x8/x16 slot into PCIe v3.0 x4 internally:

  • With a plain dumb adapter, you are limited to x4 PCIe v2.0, real world ~1450MB/s.
  • With a x8 PCIe switched adapter you are limited to x8 PCIe v2.0 that the switch convert internally to PCIe v3.0 x4, real world ~2950MB/s.
  • With a x16 PCIe switched adapter you are limited to x16 PCIe v2.0 that the switch convert internally to PCIe v3.0 x4, real world ~3200MB/s for one blade and ~6200MB/s for two or more blades.

PCIe switched cards start at around US$ 190 for IO Crest IO-PCE2824-TM2 (aka Syba SI-PEX40129), the most used by MP5,1 owners that want high performance is HighPoint SSD7101A-1, at around US$ 350~400 price point.

Please read the first post of the stickie below:

What you said is very rare. So rare that I made an account just to confirm this with you.

I have a 250GB nvme Samsung 960 drive that's going to be upgraded with a 1TB drive and will then be shelved. To avoid hardware collection dust I want to throw the 250GB into a very old system that I still use everyday. I built it well and it still does what I need.

Old system motherboard:
Gigabyte EP45 UD3P--slots are pci-e2.0 and I believe the board supports bifurcation if relevant.

What I want to confirm is this: If I buy a regular 'dummy' x8 pci-e3.0 nvme adapter card and plug a x4 nvme drive into it and then place that card into a x8 pci-e2.0 slot, will I only see x4 pci-e2.0 speeds from the drive or will the the card be able to utilize the whole x8 pci-e2.0 slot? You were very clear about what you wrote but before I throw down cash I wanted to be sure that I do indeed need a switch adapter card for this situation.

Thank you for your time.
 

tsialex

macrumors G4
Jun 13, 2016
10,869
11,358
What you said is very rare. So rare that I made an account just to confirm this with you.

I have a 250GB nvme Samsung 960 drive that's going to be upgraded with a 1TB drive and will then be shelved. To avoid hardware collection dust I want to throw the 250GB into a very old system that I still use everyday. I built it well and it still does what I need.

Old system motherboard:
Gigabyte EP45 UD3P--slots are pci-e2.0 and I believe the board supports bifurcation if relevant.
Nope, you are mistaken. Intel PCI Express Lane Partitioning is a X299/C422 and newer high-end chipsets exclusive resource. No C2D chipset have it.
What I want to confirm is this: If I buy a regular 'dummy' x8 pci-e3.0 nvme adapter card and plug a x4 nvme drive into it and then place that card into a x8 pci-e2.0 slot, will I only see x4 pci-e2.0 speeds from the drive or will the the card be able to utilize the whole x8 pci-e2.0 slot? You were very clear about what you wrote but before I throw down cash I wanted to be sure that I do indeed need a switch adapter card for this situation.

Thank you for your time.


Anyway, installing a x4 device on a wider slot still works at x4, all M.2 devices are PCIe x4 devices or narrower, installing a M.2 device in a X8 or X16 slot won't magically make it any faster. The only way to overcome the PCIe v2.0 throughput limitation is via a PCIe switched card where the wider and slow PCIe v2.0 x8/x16 slot is internally converted to narrow and fast PCIe v3.0 x4, but a so old BIOS motherboard would have support for it?

Gigabyte EP45-UD3P is a 2008ish BIOS PC motherboard without NVMe support for boot, NVMe requires that the PC firmware and Windows are both UEFI for boot support, so, why even bother?
 
Last edited:

Popyacap

macrumors newbie
May 22, 2022
3
0
Nope, you are mistaken. Intel PCI Express Lane Partitioning is a X299/C422 and newer high-end chipsets exclusive resource. No C2D chipset have it.



Anyway, installing a x4 device on a wider slot still works at x4, all M.2 devices are PCIe x4 devices or narrower, installing a M.2 device in a X8 or X16 slot won't magically make it any faster. The only way to overcome the PCIe v2.0 throughput limitation is via a PCIe switched card where the wider and slow PCIe v2.0 x8/x16 slot is internally converted to narrow and fast PCIe v3.0 x4, but a so old BIOS motherboard would have support for it?

Gigabyte EP45-UD3P is a 2008ish BIOS PC motherboard without NVMe support for boot, NVMe requires that the PC firmware and Windows are both UEFI for boot support, so, why even bother?
Thanks for the confirmation. I appreciate your detail and your time to answer.

I was sure I read that this board had bifurcation. No matter. I believe you.

"[W]hy even bother?"--Because I will have an m.2 drive sitting on the shelf doing nothing. This gives me an opportunity to mess around and hack a bios up or make a thumb-drive booter. Even if the drive is only used as a secondary drive, to me, is better than sitting on the shelf. The old pc in question is well built and had good parts chosen up front when built. It gets used daily and even though its old, it still holds its own as an archive, a download machine, browser, for audio editing and even video editing. It runs Windows 10 very well. It was good enough before; its still good enough now.

Now I know that I would need a switched adapter. This is too costly an add-on for this machine but it is very cool to know such a card exists. I have ordered a basic adapter for about $20. Whatever speeds I get I am sure will be better than SATA II. And even if it doesn't work out I have family that do have newer machines that I could put this adapter card and drive into.

Thanks man.
 

EdMun

macrumors newbie
May 31, 2022
12
1
Otautahi
installing a M.2 device in a X8 or X16 slot won't magically make it any faster.

I don't understand why, at least one (possibly both) generic cards in my 3.1 with 970 Evo Plus SSDs runs about 30MB/s R 50MB/s W faster x16 @ 765 MB/s R 725 MB/s W
 

thrush

macrumors newbie
Jul 22, 2002
9
0
  • With a x16 PCIe switched adapter you are limited to x16 PCIe v2.0 that the switch convert internally to PCIe v3.0 x4, real world ~3200MB/s for one blade and ~6200MB/s for two or more blades.

PCIe switched cards start at around US$ 190 for IO Crest IO-PCE2824-TM2 (aka Syba SI-PEX40129), the most used by MP5,1 owners that want high performance is HighPoint SSD7101A-1, at around US$ 350~400 price point.

SI-PEX40129 vs StarTech PEX8M2E2

any speed diff between these running 2 blades? Same switches?

any issues with either one blade running/booting mac os and win 10 on the other?
 

tsialex

macrumors G4
Jun 13, 2016
10,869
11,358
SI-PEX40129 vs StarTech PEX8M2E2

any speed diff between these running 2 blades? Same switches?

Both cards have the same ASM2824 switch.

any issues with either one blade running/booting mac os and win 10 on the other?

I personally have a HighPoint SSD7101A-1 that is PLX/AVAGO/Broadcom PEX8747 based and where UEFI Windows 8.1/10/11 boot is correctly supported when installed in a MacPro, so, I can't answer if Windows is correctly supported with the ASM2824 based cards. Maybe someone else can answer you about that if you ask in the thread below:

 
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