03-02-2018 06:29 AM
the PSREF document for the T480 mentions that the M.2. 2280 SSD slot has 4 PCIe lanes (see http://psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad%20T480/ThinkPad_T480_Platform_Specificatio...). However the german site campuspoint.de who sells campus models of the T480 states that the M.2 2280 SSD slot in this model (unlike the T480s) is limited to 2 PCIe lanes, just as on the previous T470. I wanted to be sure and asked them, and here is their reply:
We were stumbling over the same point in the PSREF. The difference to the former Models like T470 and T570 made us suspicious, since the new models use a very similar Adapter. So, we made a simple test. We took a T580 with a Samsung PM981 SSD, which should be able of up to 3200 Mb/s of read performance and made a simple benchmark. Our test showed a read performance of roughly 1800 Mb/s at max. This is about the same score as we had with the T470 and T570 Models and just slightly under what is theoretically possible with two PCIe Lanes.
It looks like Lenovo just didn’t mention the restriction by the Adapter. This has nothing to do with Campus Models or not. The Campus Models use the same parts as used in other Thinkpad models.
As you mentioned the T480s doesn’t have this issue.
Can Lenovo confirm there is a mistake in the PSREF of the T480 and T580 with respect to the number of lanes for the M.2 2280 SSD slot?
03-02-2018 01:48 PM
You aren't the only one (Although it is an E480):
03-03-2018 04:16 AM - edited 03-03-2018 04:19 AM
I don't know if the difference between PCIe x2 or x4 is noticeable in general use, probably not unless you transfer massive amounts of data. I wonder if this questionable design choice was not made necessary to allow 2 PCIe lanes for an additional SSD placed in the WWAN slot?? Anyway I really find it terrible that Lenovo is unable to provide reliable information on the PSREF, especially when it comes to professional systems such as the Thinkpad T series!
03-03-2018 01:53 PM
My understanding is that the WWAN is x2 and the standard port is x4. That's what it says in the PSREF and has been discussed at reddit.
In terms of real life performance, unless you do 4K video editing and write 10+ GB files at once, there is no difference between SATA and PCIe x2 or x4. Only in benchmarks.
03-04-2018 01:37 AM
Standard port might be x4 but the M.2 2280 SSD is attached via an adapter which apparently only uses 2 lanes. This is at least what the benchmarks on the T580 and reviews on the T470/T570 have shown. And the adapter has exactly the same FRU number in the T480 and T470. I guess the PSREF is either wrong or misleading. In the T470 it correctly refered to x2.
03-04-2018 01:48 AM
The t470 indeed only has 2x lanes. I would have thought the adapter is only a mechanical part with no say on the number of lanes. The number of lanes depends only on the motherboard and CPU.
One of them is wrong. Let' see which one.
03-05-2018 01:19 PM
Just had the same questions come up when I received a P52s last week. PSREF doc for the P52s also said the M.2 2280 SSD has four lanes. After checking with HwInfo and running benchmarks I have confirmed it is actually limited to two lanes and not 4 as the PSREF says.
I cannot confirm for the T480 and T580 but I can confirm the innaccuracy of the PSREF documents. It is likely that they are also limited to 2 lanes.
03-07-2018 11:08 AM
Users on reddit who bought the T480 have now confirmed that the version with the MX150 nVidia discrete graphics have their NVMe PCIe limited to 2x lanes.
Maybe the version without the discrete graphics has all 4 lanes availalbe to the NVMe drive.
03-23-2019 05:27 PM
Maybe late reply, but I have a T580 with no dGPU.
I ordered it with a 512GB SSD which turns out to be a WD SN720 (2280) in the drive caddy; the SSD is capable of x4 PCIE 3.0 lanes but as connected in the T580 it's only getting x2 lanes.
I also added a WD SN520 (2242) in the WWAN slot; the SSD is also capable of 4x PCIE 3.0 lanes but it is also only getting x2 connected lanes from the WWAN slot.