If you can use X1 card in X16 slot, why also "negotiable x16/x4/x1"?

I just bought a Lenovo M910t desktop machine. The case has four expansion slot spacers on the rear, although there are only three expansion slots on the motherboard itself: x16, x1, and negotiable x16/x4/x1. The second x16/x4/x1 slot has that fourth "blank" space next to it on the rear, so that you can install a double-wide card in both the primary x16 slot as well as the secondary x16/x4/x1 slot. Sounds good.

My problem is that I want to install one double-width x16 graphics card, along with two x1 TV tuner cards. But I can't put the double-width graphics card in the primary x16 slot since the double-width will obscure the x1 slot right below it, thus eliminating it for my use.

So the only possible solution is to put the double-width graphics card in the secondary x16/x4/x1 slot (with the second half simply occupying the extra "blank" space left for it in the motherboard and case design), and then put one x1 card in the primary x16 slot, and the second x1 card in the x1 slot (since it is not going to be obscured by the single-wide x1 card just above it). I've read that you can install an x1 card in an x16 slot and it will work just fine.

So if this above approach will truly "work just fine", then what is the reason for them to label that secondary x16/x4/x1 slot as "negotiable"? What does that actually mean? How does the behavior of that slot differ from the primary x16 slot which isn't labeled "negotiable" but which apparently can still be used for x1??

Is there some performance difference from using an x1 card in an x16 slot vs. using the same x1 card in a "negotiable" x16/x4/x1 slot?

Is there a performance downside or negative impact from using the "negotiable" x16/x4/x1 slot vs. the primary x16 slot for the x16 graphics card?

Is there some performance improvement (individually or overall) to using the negotiable x16/x4/x1 slot for an x1 card instead of using the primary x16 slot for that x1 card?

If I had a motherboard with more than just these three expansion slots I'd be sure to use two x1 slots for the two x1 cards. But since I don't have much of a choice here (other than going with a single-wide x16 graphics card and putting it in the primary x16 slot, thus allowing my two x1 cards to go into the official x1 slot as well as the negotiable x16/14/x1 slot) I'd really like to learn what is the meaning of "negotiable", if I can just go ahead and use the primary x16 slot anyway for an x1 card.

PCIe x16, x4, x1 is to do with the number of PCIe lanes available. Some devices, such as graphics cards need more lanes. Other devices, such as WiFi cards and SSD expansion cards, typically only require x4 lanes.

You can use a x1 card in a x1, x4 or x16 lane slot if need be. So you could use the x1 card on the primary or secondary PCIe x16 interface. However, this is actually nothing to do with what "negotiable" means.

A "negotiable" PCIe slot would likely mean negotiable with the M.2 SSD slot. In other words, if you have no drive plugged in to the M.2 slot, then you are free to use the secondary PCIe interface. If, on the other hand, the M.2 SSD connector is in use, then you would be unable to use the secondary PCIe interface as a device connector.

You will find that this secondary x16 PCIe / M.2 slot "negotiable" combination is on a lot of motherboards these days.

iko22 said:

PCIe x16, x4, x1 is to do with the number of PCIe lanes available. Some devices, such as graphics cards need more lanes. Other devices, such as WiFi cards and SSD expansion cards, typically only require x4 lanes.

You can use a x1 card in a x1, x4 or x16 lane slot if need be. So you could use the x1 card on the primary or secondary PCIe x16 interface.

I see. Good news.

Didn't remember this, although I do recall now trying to use an X1 card in a second x16 slot (intended for an SLI setup) on a motherboard with 7 expansion slots once, and it worked. So I guess I should have known this.

Anyway, thank you for the info.

However, this is actually nothing to do with what "negotiable" means.

I knew it. Now for the bad news.

A "negotiable" PCIe slot would likely mean negotiable with the M.2 SSD slot. In other words, if you have no drive plugged in to the M.2 slot, then you are free to use the secondary PCIe interface. If, on the other hand, the M.2 SSD connector is in use, then you would be unable to use the secondary PCIe interface as a device connector.

This is terrible news, if it's true that the secondary becomes completely unavailable if an M.2 SSD slot is also present on the motherboard and in use. Sharing the potentially available 16 lanes with the M.2 slot makes more sense than having this secondary slot completely unavailable at all if an M.2 SSD is in use.

The full-speed M.2 PCIe SSD drives (like Samsung NVMe) use PCIe PCIx4. So if the M.2 slot shares PCIe lanes with this secondary "negotiable x16/x4/x1" I would have guessed could mean that if the M.2 drive is present and using x4 then the negotiable secondary slot would only be usable for less than the total 16 lanes shared between this slot and the M.2 slot. In other words this secondary negotiable slot would now only be usable for x4 or x1 cards, but not the full x16. So you couldn't put an x16 graphics card here if you also had an x4 M.2 SSD installed. But I could still use it for one of my two x1 TV tuner cards.

But if you weren't using an M.2 SSD then you could indeed use the full x16 of this secondary slot for a graphics card.

And, naturally, I DO have an x4 M.2 drive installed as well. So going with the assumption that the M.2 slot shares PCIe lanes with this negotiable x16/x4/x1 secondary slot, that means I couldn't move my double-wide x16 graphics card to this slot after all, no matter that Lenovo provided the space for it. I could only do that if I wasn't also using an M.2 drive.

I guess this is why I've always built my own machines, so that I could pick my "big boy" motherboard typically with seven expansion slots, not three. I guess that's the price you pay for "store bought" even if you're going to upgrade it yourself after-market.

Looks like I'll have to go with a single-slot x16 graphics card installed in the primary x16-only slot. I discovered such a thing I hadn't known existed, in an Inno3D 1-slot version of a GTX 1050ti which I was able to find available from a German online retailer yesterday for $188, no tax and free shipping. All American-available versions of this card I've ever seen have been dual-wide, including both full-size as well as Gigabyte low-profile. And the dual-wide card inevitably always obscures one x1 slot immediately to its south. Not a problem if you have more x1 slots, but if this is the only one on the motherboard you're in trouble.

Your explanation of what "negotiable" really means makes sense. I now remember seeing someone complain about this "shared PCIe lane" design between M.2 and something else on the PCIe bus in a recent Lenovo laptop, thus limiting an installed M.2 NVMe drive to only 2 lanes and thus half of its true rated speed. Presumably in this M910t the shared 16 lanes lanes don't limit the M.2 x4 speed but only limit the secondary expansion to usability by x4 or x1 cards.

The 1-slot GTX 1050ti from Inno3D has saved me. I will put it in the primary x16 slot, and put the two x1 TV tuner cards in the x1 and negotiable x16/x4/x1 slot. And I will also have an x4 M.2 SSD in the M.2 slot.

dsperber said:

I will put ... the two x1 TV tuner cards in the x1 and negotiable x16/x4/x1 slot. And I will also have an x4 M.2 SSD in the M.2 slot.

Apologies for taking a while to get back to you. I have just noticed what you are attempting to do and I do not think it will quite work in that way.

The problem is that the two slots, the secondary PCIe and the M.2, are not that "negotiable" on a lane by lane basis.

In reality, if you try and insert a card into one of the slots, then the other slot/chipset will automatically disable from use. Which way round depends on the motherboard. Either the M.2 disables the secondary PCIe, or the other way round.

Hope that helps.

Well, today's the day I will probably find out. the new Lenovo M910t comes out of its carton and starts its build-out this morning.

Still haven't received the Inno3D 1-slot GTX 1050ti yet but the two that I ordered have been shipped last Friday from somewhere in Europe, via PostNL Tracking status shows that as of yesterday 1/7 it was processed, sorted, and now "in transit to the USA". So maybe by end of week or thereabouts.

In the meantime I will temporarily use the same 2-slot EVGA GTX 1050ti SC I removed from my macine that died. And temporarily the plan is to use just one of my two TV tuner cards in the remaining x16/x4/x1 negotiable slot... however that works, I will soon find out.

The plan is eventually to have the 1-slot 1050ti and the two tuner card in the three slots. that's the objective, if it works.

And the plan is absolutely to still also have an M.2 Samsung 970 EVO in the M.2 slot as the primary drive. I will aso have a 6TB 3.5" SATA3 HDD spinner in the primary drive bay, and two more 2TB 3.5 SATA3 HDD spinner in a single vented external 2-bay USB 3.0 enclosure. These are the three data drives from my dead machine. I will soon find out if I can actually run the 970 EVO at x4 speed while also having that x16/x4/x1 slot occupied with an x1 TV tuner card.

There is a second internal 2.5" SATA3 drive bay that I'm not plannong on using at the moment. But worst case, if the M.2 slot is somehow unusable or badly degraded (say to x2, or non-functioning) I may opt to just go with a 2.5" SATA3 SSD. Doesn't provide the same performance as an NVMe drive but it still is significantly faster than a 2.5" HDD spinner in that bay. This drive, and what it is and how fast it is, is very important since this drive is where Win7 will live (along with another partition or two for "fast data").

That's the plan anyway. We will find out today just exactly what is actually acceptable regarding use of that negotiable slot as well as M.2 since even this day-1 configuration will use both items.

We shall see.

Time to follow up, now that the M910t has been built-out.

Still haven't received the 1-slot GTX 1050ti graphics card yet so for the time being I'm using my original 2-slot EVGA GTX 1050ti SC in the primary x16 slot which obscures the adjacent x1 slot. But the third "negotiable x16/x4/x1" slot is still visible and available. So that's where I inserted one of my two TV tuner cards, namely the Ceton 4-tuner cablecard-enabled InfiniTV4. I can get local network channels via Spectrum and this card, so I don't really require the second Hauppauge OTA/ATSC 2-tuner card although I really do want to use it when room permits.

And I've got my 6TB WDC Black drive in the primary 3.5" SATA3 drive bay. Nothing in the secondary 2.5" SATA3 drive bay. My other two 2TB WDC Black drives are in a 2-bay vented external USB 3.0 Yottamaster enclosure. Can't say enough good things about this external drive enclosure.

Now I already had another external 2TB USB 3.0 Verbatim drive that I use for backups. It is managed by Green Button software (that came with the drive) which spins it down after 10 (or whatever you set) minutes of inactivity, to minimize wear and tear on the drive as well as minimizing heat, electricity use, and noise. They automatically spin back up when next accessed.

Surprisingly the new Yottamaster external USB 3.0 enclosure (with its two SATA3 drives inside) is now also being managed by the Green Button software! In other words my two 2TB drives will also be spun down after 10 minutes of inactivity same as happens with my Verbatim backup drive. Didn't expect this, but I'm very pleased.

And I do have the Samsung 970 EVO M.2 NVMe SSD installed in the M.2 slot of the M910t. The Windows C-partition lives on this drive along with several other "data" partitions.

Now as to the question about whether or not having the x1 TV tuner card in the "negotiable x16/x4/x1" slot would in some way either impact the performance of the M.2 drive, or whether it was even possible to use this slot along with an installed M2 drive, I can now report that there appears to be ZERO IMPACT!!

In other words: IT WORKS PERFECTLY!

There is zero impact on M.2 functionality or performance, as confirmed by Crystal DiskMark. Getting about 3500MB/s before I installed the TV card, and the same speed after I installed the TV card. And the TV card works perfectly, as apparently does the M.2 card as well.

So I think I now interpret the "negotiable" to mean just exactly what the word implies, namely that depending on the requirements of whatever card you install in this slot, that is what speed the slot will provide. So say you install an x4 PCIe-to-M.2 daughtercard (which requires 4-lanes for full speed), that's what will be provided. If you install an x1 TV tuner card (which only requires 1-lane), then that's what will be provided. It appears to be totally independent of the 4-lanes being provided to the PCIe M.2 connector.

When the 1-slot GTX 1050ti card arrives (probably next week) I will replace the 2-slot EVGA GTX 1050ti SC, thereby now exposing the adjacent x1 slot for use. And I will then install the Hauppauge 2-tuner OTA/ATSC card in that x1 slot, adding it to Windows Media Center just as used to be the case in my ASUS machine.

So I'm back in business with the new M910t replacing my former and now dead home-built ASUS machine. Only hiccup to my overall plan was that I had intended to replace the stock 250W PSU in the M910t with a fanless 600W Seasonic PSU (which I'd bought for the dying ASUS machine when I thought it was a PSU problem). This objective has met with failure.

The problem is that the Seasonic PSU is a standard ATX-size power supply (3 5/8" x 5 7/8" x 6 11/16"). Unfortunately Lenovo's recent tower cases is reduced in "depth" by several inches from the previous generation of tower cases and so they use a smaller than standard PSU (3 5/8" x 5 7/8" x 5 1/2"). That's about 1 1/4" shorter in its long edge than the standard ATX PSU, and unfortunately that turns out to be critical inside these recent smaller Lenovo tower cases. The 3.5" / 2.5" drive assembly inside the case is on a swing-up/down hinge mechanism, and in its swing-down closed orientation it hits the longer length of the standard ATX PSU box. The 1 1/4" shorter Lenovo PSU turns out to be critical to allow the swing-down drive bay assembly to close completely and lock.

So after taking an hour to swap power supplies with the drive assembly up (and out of the way of my work), I finally swung it down to close, and it wouldn't close. Ranted and raved, and then spent another 30 minutes swapping back the original Lenovo PSU. Turns out as "skimpy" as 250W is, it's still more than enough to handle the additional GTX 1050ti card (max 75W but generally uses about 38W) and the one or two TV tuner cards. So I'll just have to live with the 250W Lenovo PSU.


Bottom line: "negotiable" simply means "variable, depending on card requirements". It is seemingly completely independent of the M.2 storage connector.

Just wanted to add a bit of closure to this subject...

Finally received my 1-slot Inno3D x16 GTX 1050ti card and have installed it in my M910t in the primary x16 slot, replacing the 2-slot EVGA GTX 1050ti SC (thus freeing up the x1 slot which was between the primary x16 slot and the negotiable x16/x4/x1 slot). And I've now also installed the Hauppauge x1 HVR-2250 2-tuner OTA/ATSC TV tuner card that was awaiting the space for it. And there already is the Ceton x1 InfiniTV4 4-tuner cablecard-enabled TV tuner card which I'd placed in the negotiable x16/x4/x1 slot, which is still there. And there is also the Samsung 970 x4 Evo M.2 NVMe SSD which is installed in the PCIe M.2 slot, along with the 1TB HDD spinner in the primary 3.5" SATA3 drive bay.

And I can report that everything works perfectly. No performance degradation anywhere, and all cards are operating properly as hoped.

So I again conclude that "negotiable x16/x4/x1" means just that, namely that it can perform with either of those three speeds depending on the requirements of the card you insert into that slot. But it's totally independent of the other two x16 and x1 slots, and also independent of the M.2 connector which is just another x4 drop on the PCIe bus.

So I'm back in business, having successfully replaced my old ASUS P8Z77-V Pro machine with seven expansion slots that died with this new M910t that has just three expansion slots. Most importantly, I have the graphics card I wanted to use (albeit in 1-slot form rather than 2-slot form), along with the two TV tuner cards I wanted to use... and I also have an M.2 NVMe primary drive for Windows and a 3.5" 6TB SATA3 HDD spinner for WMC recording.

Good as new.