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[Solved] NVME slow when booting from it, fast when booting from a SATA HDD

Joined
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Hi,

I've done a clean installation of Mac OS X 10.13.5 on a Gigabyte Z170X UD5 TH motherboard. Several SATA HDDs are connected as well as a Samsung 970 PRO 512GB SSD. When I boot from the NVME the NVMEExpress section in the 'System Report' reports 'Link Width: x1' and write/read speeds as reported by "BlackMagic Disk Speed' are around 750 MB/sec. When I boot 'clone' of the NVME drive from a SATA SSD, 'System Report' reports 'Width: x4' in the NVMEExpress section and I get read/write speeds of 2215/2781 MB/sec. The Model Identifier is set to MacPro6,1.

This puzzles me since both drive contain a 1:1 copy of each other.. Could somebody point me in the right direction to solve this issue ?

Thanks for reading..
 
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NVME shares lanes with other stuff on a Z170x-UD5-TH. For example, the PCIe x4 slot. Make sure you are not using both. I doubt if that's the problem here, though. Is your BIOS up-to-date? Why are you using Mac Pro 6,1? iMac 14,2 or 17,1 is much closer to a Z170x...
 
Joined
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Dell XPS 15 9570 (Clover UEFI)
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NVME shares lanes with other stuff on a Z170x-UD5-TH. For example, the PCIe x4 slot. Make sure you are not using both. I doubt if that's the problem here, though. Is your BIOS up-to-date? Why are you using Mac Pro 6,1? iMac 14,2 or 17,1 is much closer to a Z170x...

I've done some further testing since I posted my message earlier today. The same issue seems to exist under Windows. After rebooting multiple times I've just found out that the 4x speed while booting from a SATA HDD was a matter of 'statistical probability'. Most of the time the link speed is 1x and in rare cases it's 2x or 4x. I'm assuming it's the motherboard here that's to blame. I'm still using the F20 BIOS which I patched for activating NVRAM. Since there is nothing I need that is patched in newer BIOS versions I prefer not to brake something since there could be issues with downgrading the BIOS version. With the Mac Pro 6,1 profile everything seems to just work OOB (with a little help of Clover), including sleep states etc. I've had similar results with the iMac 14,2 profile, but in an attempt to get an AMD RX580 and a GTX980 to work together in the same machine I've explored the Mac Pro 6,1 option. I could get it to work by renaming the GPUs to GFX1 but this didn't give me 5K resolution on a MST monitor anymore, so I gave up and moved the GTX980 to a TB3 enclosure which I enable when I want to boot to Windows for using software which relies on CUDA.

Regarding the iMac 17,1 profile.. It seems to cause some issues where it doesn't wake from sleep anymore and requires 'two' attempts to do so.

As for the solution.. It seems a PCI-e to m.2 adapter will do the trick from what I found out.

Thanks for the reply !
 
Joined
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Hi Sparc,

I have exact same problem with my Gigabyte Z170X UD5 TH
I'm aware of the PCIE Lane sharing with other devices.
I've placed my Graphics Card & other PCI-E cards in good order to make my Samsung 970 NVME working full speed!

When in High Sierra I check "System Report/NVME Express Lane Widt x4" the speed is perfect around 2200/2800
When I reboot the system or boot it up the next day for example I get "System Report/NVME Express Lane Width x2" or sometimes even "Lane Width x1"

I'm also using the Thunderbolt For my UAD Apollo Twin Audio Interface but I did some test with switching ports or boot without Thunderbolt but I didn't effect the "Lane Width"

Is there a solution for this strange behaviour with random 'NVME Express Lane Width?
My system is set to iMac 14,2 profile
 
Joined
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Hi vipermachine,

No I’ve never found a solution and think it’s a design flaw on the motherboard. I’ve added a PCI-e to m.2 adapter and that solved the issue for me.

For what it’s worth, the same issue exists when booting Windows, so it’s not related to your MacOS configuration.

There is a small chance that a BIOS update would solve it. Since however updating to the latest BIOS version, but since that disables native NVRAM support I’ve never tried that.
 
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Hi Sparc,

Thanx for your Reply.

Bios= F22a

I did some testing and try to figure out why
started from scratch with no PCI-E or Sata drives attached!
I used the intel graphics.
It still give me sometimes lane width x4 and Sometimes lane width x2 (or even x1)
Its like there is a ghost in Bios:)


My guess its a problem with Samsung EVO 970.
I found nothing on the forum wit similar problems
It doesn't make sense that sometimes it boots and "Lane Width x4" and sometimes "Lane Width x2"
I don't think this is a Clover related problem or APFS

SO you are right!

I ordered a Pci m2 adapter today :)

Thanx for reading
 
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@vipermachine
I wonder if this adapter will fits: 970 PRO 512GB NVMe PCIe M.2?

 
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