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Negotiated current link speed NVME drive at 2.5 GBPS after Mod..
#1
Hi,

I have a MSI Godlike X99A with a 6850K CPU that I have modded to allow bifurcating the last PCI-E Slot on the motherboard in half from 8X to 4X4X operation. Such that with an adapter like the Supermicro  RSC-R2UU-2E4R 2U PCIE I am able to run my onboard M.2 at 4X speed along with a Plextor NVME x4 drive on the last PCI-E slot at the same time where as before it was not possible to without setting the M.2 to PCH Mode. Anyhow the problem is sometimes when I boot up HWinfo says the current link speed for the Plextor is 2.5 Gbps where as sometimes its a 8.0 Gbps. I noticed that my video cards sometimes do the same thing until they are put under load so I wonder if its something similar? Got link state power management disabled in Windows power plan settings as well.

So I'm a little confused on whats going on:

[Image: samsung4x.png?raw=1][Image: plextor4x.png?raw=1]
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#2
For GPUs it's a normal power management feature to switch the link to a lower speed (2.5 GT/s) when it's not used, so I assume it's the same case for the NVMe too.
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#3
Yeah but for an NVME drive how the hell do you set it to stay at full speed 8.0 GT/S ?!!!

Thanks
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#4
Sorry, I don't know. I think it will automatically switch to 8 GT/s when needed, so don't understand why do you want to stay it at that speed all the time.
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#5
(01-01-2018, 10:04 PM)Martin Wrote: Sorry, I don't know. I think it will automatically switch to 8 GT/s when needed, so don't understand why do you want to stay it at that speed all the time.

Well I tried to run AS-SSD benchmark and did not notice any change in the link speed. However as its GPU counterpart has the ability to shift into high gear it would seem that this link speed may not need to be set with hardware initialization stage at post but could be in software. So did the next best logical thing which was to install the latest drivers I could find but in the past Plextor never released any drivers for it and it just used Windows standard nvme drivers. Got lucky though browsing through Win-Raid.com and found actual Plextor drivers and installed them. So far so good. Got 8.0 GT/S link speed after two reboots. Time will tell if its permanent. Only thing is Samsung Magician for my other NVME drive is failing to start now. If If this works Samsung Magician can get lost!

Thanks
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#6
Figured out how to use SETPCI to change the link speed. Seems like it works sometimes and sometimes not.
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