Please help to understand how Pcie works for ssd.

[keavlar]

Hey all.

I already had a topic that touched this theme a little.

But after long searches, I was still unable to understand how the whole thing works.

I have Asus hero 7 MB and Samsung 970evo pro. Specs. Attached. 

While my top Pcie slot  used by gpu gtx 1070 gaming x

I still has  1 pcie x3 slot available.

Can i or can not use it for the ssd, to get max performance???

[keavlar]

 the x4. And x16 the difference in pins right?

The pcie 2.0 or 3.0 is what matters, right?

[mariushm]

 

There's two kinds of pci-e lanes:

1. PCI-e 2.0 uses lanes that have a maximum speed of 500 MB/s

2. PCI-e 3.0 uses lanes that have a maximum of 970 MB/s

 

M.2 SSDs can use up to 4 pci-e lanes to communicate with the PC. It's UP TO because some SSD controllers are designed to use maximum 2 pci-e lanes because it makes the controller chip cheaper. 

Also, by design, all M.2 SSDs will work with less lanes than they were designed to, so for example, a pci-e x4 M.2 SSD would also work with 2 lanes, or with 1 lane.

 

The two red pci-e slots are connected directly to the processor.

The Z97 chipset creates a bunch of pci-e 2.0 pci-e lanes, and these are connected to the pci-e x1 slots and to that M.2 connector.

On this motherboard, those pci-e lanes are connected to the 3 pci-e x1 slots, the pci-e x4 slot and the M.2 connector.

The M.2 connector receives 2 pci-e 2.0 lanes from the chipset, which means the M.2 connector can do up to 2 x  500 MB/s in both directions.

If you insert a M.2 SSD into that connector, because there aren't enough pci-e lanes created by the chipset, one of the pci-e x1 slots is turned off (its pci-e x1 lane is redirected to the M.2 connector) and the black pci-e x16 connector that's normally pci-e x4 either becomes x1 or x2, or becomes disabled as well. Simply put, the Z97 chipset doesn't create enough pci-e 2.0 lanes to give lanes to all slots at the same time. 

 

Now, if you want more speed, one of the options you have is to buy a pci-e x4 to M.2 adapter card, like this one for example:

 

M.2 NGFF to Desktop PCIe x4 x8 x16 NVMe SATA Dual SSD PCI Express Adapter Card

Pci-E X4 To M.2 Ngff M/B Key Ssd Sata Adapter Converter Card For Desktop Pc E9H2

 

(only bottom m.2 is nvme,using pci-e, the top connector is like a bonus, allowing you to insert a SATA only m.2 SSD there and then connect it to PC using a regular SATA cable)

 

So, if you leave the original M.2 connector unused, and you leave that pci-e x1 slot that shares lanes with pci-e x4 slot unused, you'll have the black pci-e x16 slot with the maximum number of pci-e 2.0 lanes possible, which is 4. 

Using that adapter card, your M.2 SSD will use 4 pci-e lanes, but they'll be pci-e 2.0 lanes, which means the maximum speed will be 4 x 500 MB/s in both directions.

 

Now, the two red pci-e x16 slots receives pci-e lanes from the CPU. Both can do 16 pci-e 3.0 lanes, but if you have two cards or two devices in the slots, each slot receives 8 pci-e 3.0 lanes from the CPU.

So if you install just one video card in one of the slots (shouldn't matter which one), that video card will run at pci-e x16 speed.

IF you install a second video card or any device (ex a 10gbit network card), the slots automatically become pci-e 3.0 x8

 

So what you could do, is take that pci-e to M.2 adapter card I linked above and insert it in one of those red pci-e slots.

Then, your video card will automatically run at pci-e 3.0 x8 speed (half)  and the pci-e to M.2 adapter card will receive 8 pci-e 3.0 lanes but will only use 4 pci-e 3.0 lanes, because that's the maximum the M.2 connector supports.

It means your M.2 SSD will have up to 4 x 970 MB/s speed in both directions.

 

This would be the fastest speed for a M.2 SSD you could have on your motherboard, but as you can see the downside is your video card will be a tiny bit slower because it will only have 8 pci-e lanes.

 

It's worth noting that your bios may not recognize the M.2 SSD as a bootable drive if you insert it into those red pci-e x16 slots using an adapter card. It will work perfectly fine as storage drive, but may not be able to run windows from it. I'm not sure, your motherboard may be new enough that it will be detected just fine.

 

My advice would be to get one of those adapter cards but use the third pci-e x16 slot which only has 4 pci-e 2.0 lanes, giving the SSD up to 2 GB/s.

Your SSD can reach faster transfer speeds, but in real world very rarely you'll read or write files from your SSD at speeds higher than 1-2 GB/s, so you won't really feel the SSD as being slow. 

However, if you use the adapter in the red slots, you're probably gonna feel something like 0.5-1% performance drop on the video card and it's not worth it.

 

[keavlar]

52 minutes ago, mariushm said:

 

There's two kinds of pci-e lanes:

1. PCI-e 2.0 uses lanes that have a maximum speed of 500 MB/s

2. PCI-e 3.0 uses lanes that have a maximum of 970 MB/s

 

M.2 SSDs can use up to 4 pci-e lanes to communicate with the PC. It's UP TO because some SSD controllers are designed to use maximum 2 pci-e lanes because it makes the controller chip cheaper. 

Also, by design, all M.2 SSDs will work with less lanes than they were designed to, so for example, a pci-e x4 M.2 SSD would also work with 2 lanes, or with 1 lane.

 

The two red pci-e slots are connected directly to the processor.

The Z97 chipset creates a bunch of pci-e 2.0 pci-e lanes, and these are connected to the pci-e x1 slots and to that M.2 connector.

On this motherboard, those pci-e lanes are connected to the 3 pci-e x1 slots, the pci-e x4 slot and the M.2 connector.

The M.2 connector receives 2 pci-e 2.0 lanes from the chipset, which means the M.2 connector can do up to 2 x  500 MB/s in both directions.

If you insert a M.2 SSD into that connector, because there aren't enough pci-e lanes created by the chipset, one of the pci-e x1 slots is turned off (its pci-e x1 lane is redirected to the M.2 connector) and the black pci-e x16 connector that's normally pci-e x4 either becomes x1 or x2, or becomes disabled as well. Simply put, the Z97 chipset doesn't create enough pci-e 2.0 lanes to give lanes to all slots at the same time. 

 

Now, if you want more speed, one of the options you have is to buy a pci-e x4 to M.2 adapter card, like this one for example:

 

M.2 NGFF to Desktop PCIe x4 x8 x16 NVMe SATA Dual SSD PCI Express Adapter Card

Pci-E X4 To M.2 Ngff M/B Key Ssd Sata Adapter Converter Card For Desktop Pc E9H2

 

(only bottom m.2 is nvme,using pci-e, the top connector is like a bonus, allowing you to insert a SATA only m.2 SSD there and then connect it to PC using a regular SATA cable)

 

So, if you leave the original M.2 connector unused, and you leave that pci-e x1 slot that shares lanes with pci-e x4 slot unused, you'll have the black pci-e x16 slot with the maximum number of pci-e 2.0 lanes possible, which is 4. 

Using that adapter card, your M.2 SSD will use 4 pci-e lanes, but they'll be pci-e 2.0 lanes, which means the maximum speed will be 4 x 500 MB/s in both directions.

 

Now, the two red pci-e x16 slots receives pci-e lanes from the CPU. Both can do 16 pci-e 3.0 lanes, but if you have two cards or two devices in the slots, each slot receives 8 pci-e 3.0 lanes from the CPU.

So if you install just one video card in one of the slots (shouldn't matter which one), that video card will run at pci-e x16 speed.

IF you install a second video card or any device (ex a 10gbit network card), the slots automatically become pci-e 3.0 x8

 

So what you could do, is take that pci-e to M.2 adapter card I linked above and insert it in one of those red pci-e slots.

Then, your video card will automatically run at pci-e 3.0 x8 speed (half)  and the pci-e to M.2 adapter card will receive 8 pci-e 3.0 lanes but will only use 4 pci-e 3.0 lanes, because that's the maximum the M.2 connector supports.

It means your M.2 SSD will have up to 4 x 970 MB/s speed in both directions.

 

This would be the fastest speed for a M.2 SSD you could have on your motherboard, but as you can see the downside is your video card will be a tiny bit slower because it will only have 8 pci-e lanes.

 

It's worth noting that your bios may not recognize the M.2 SSD as a bootable drive if you insert it into those red pci-e x16 slots using an adapter card. It will work perfectly fine as storage drive, but may not be able to run windows from it. I'm not sure, your motherboard may be new enough that it will be detected just fine.

 

My advice would be to get one of those adapter cards but use the third pci-e x16 slot which only has 4 pci-e 2.0 lanes, giving the SSD up to 2 GB/s.

Your SSD can reach faster transfer speeds, but in real world very rarely you'll read or write files from your SSD at speeds higher than 1-2 GB/s, so you won't really feel the SSD as being slow. 

However, if you use the adapter in the red slots, you're probably gonna feel something like 0.5-1% performance drop on the video card and it's not worth it.

 

Wow.

It is an amazing explanation. Thank you vet much.

I will have to read it few times, to fully understand.

Is it ok to send you private massage if I will have any questions?

[keavlar]

4 hours ago, keavlar said:

M.2 SSDs can use up to 4 pci-e lanes to communicate with the PC.

Meaning that it can use 4 slots ?

 

4 hours ago, keavlar said:

M.2 SSDs can use up to 4 pci-e lanes to communicate with the PC. It's UP TO because some SSD controllers are designed to use maximum 2 pci-e lanes because it makes the controller chip cheaper. 

Also, by design, all M.2 SSDs will work with less lanes than they were designed to, so for example, a pci-e x4 M.2 SSD would also work with 2 lanes, or with 1 lane.

not sure I understand this part

 

4 hours ago, keavlar said:

The two red pci-e slots are connected directly to the processor.

How do you know that?

 

 in the end, i found this all messing with my head, i wish there was easy way to explain. 

[mariushm]

How do I know that red pci-e slots are coming from CPU?  From experience, from knowing about how hardware works

On most modern processors, you get 16 lanes or more from CPU which by default go to the video card slot, as the video card needs a lot of bandwidth.

Some chipsets allow those 16 lanes to be split into 2 groups of 8 lanes, and these separate groups can be wired to two separate slots. 

 

PCI Express is designed around the concept of PCI-E LANES ... each lane is a bi-directional channel of communication between a device and the host.

Also by design, there are some rules:

1. a device using pci-e MUST work with as little as a single pci-e lane to communicate with the computer.

2. the pci-e slot's physical size may indicate a number of pci-e lanes, but in reality only a certain number of pci-e lanes may be present inside the slot.

 

So you have to understand that the physical size of a pci-e slot (x16 , x4) does not always correlate with the number of pci-e lanes connected to that pci-e slot.

 

The M.2 connector is just a fancy right angle SLOT (that's very low height) which has a mix of pins:

* most of the contacts/pins that would be in a physical pci-e x4 slot  (the 4 pci-e lanes wires, plus 3.3v, but no 12v)

* some pins that carry the signal you would have in a SATA cable (cheaper SSD drives can use the classic SATA protocol)

* other pins that are outside the scope of this explanation.

 

A motherboard manufacturer is free to do what it wants. He can connect

* just the SATA part of the M.2 connector, in which case you can only use SATA SSDs with that connector, or

* he can only connect one or more pci-e lanes to the connector in which you say it's a nvme only M.2 connector,

* he can connect both pci-e lane(s) AND the SATA part, in which case you can use any kind of SSD

 

Also, as I explained above, the manufacturer is free to wire as little as one pci-e lane, or two pci-e lanes, or the maximum number of 4 pci-e lanes to the M.2 connector. It's a maximum of 4 because that's how many actual physical contacts are reserved for pci-e lanes. Who knows, in the future there may be more lanes... there are some contacts in the m.2 connector that are currently not used for anything.

 

On your particular motherboard, Asus decided to take 2 pci-e lanes created by the chipset and connect them to your M.2 connector. No matter what SSD you would insert in the connector, you would 

If you install a pci-e x4 M.2 SSD in the connector, there's only 2 actual pci-e lanes wired to that connector, so the M.2 SSD will work with only 2 pci-e lanes, possibly at reduced speed.

 

Now, you have to picture the chipset like a network switch, with 8 or 16 or 24 ethernet connectors, but instead of ethernet connectors you have pci-e lanes.

Some of these pci-e lanes are used inside the chipset itself to connect SATA controllers, some are used for USB 3 hubs - the motherboard manufacturer can choose to enable more SATA ports and put more physical SATA ports on the motherboard by enabling a SATA controller inside the chipset, but then there's fewer pci-e lanes going outside the chip to slots. 

 

On your particular motherboard, Asus made some choices in regards to how many SATA and USB ports you have which resulted on having a reduced number of pci-e lanes available to be routed to slots.

In order to wire everything right, they would have needed at least 11 pci-e lanes:

* 4 pci-e lanes for the third pci-e x16 slot (electrical pci-e x4)

* 4 pci-e lanes for the M.2 connector

* 3 pci-e lanes for the 3 pci-e x1 slots

However, due to how they did everything on the motherboard, they had much fewer lanes to work with, so some pci-e lanes are wired to two things at the same time (a slot and the m.2 connector at same time for example).

 

They tell you how everything works on page 40 of the manual :

 

 

 

So basically, they're using 4 pci-e lanes from chipset to connect as much as 4 pci-e slots and a M.2 connector to the chipset, but not at the same time.

You have one option in the BIOS which has several options : Auto, pci-e x1 , M.2 , pci-e x4

 

On Auto, you have 2 options :

* if there's a card installed in one of the pci-e x1 slots, the motherboard makes all black pci-e slots x1, so the black pci-e x16 slot becomes x1 as well.

* if there's no cards installed in the pci-e x1 slots but there's a card in the black pci-e x16 slot, that slot gets 4 pci-e lanes.

 

On pci-e x1 mode,  you're forcing the motherboard to keep all four slots functional at x1.

This can be useful if you have an M.2 SSD which can "talk" to the computer using either nvme (pci-e lanes) or SATA - you're disabling the nvme part of the M.2 connector and you're forcing the M.2 SSD to talk using the SATA part, at lower speeds (ex around 550 MB/s max) 

 

On M.2 mode, you're reserving 2 lanes for the M.2 connector, and that leaves the black pci-e x16 slot with only two lanes, making it a pci-e x2 slot. The other pci-e x1 slots are disabled

 

On pci-e x4 mode, you're forcing all 4 lanes to stay in the black pci-e x16 slot, disabling the other pci-e x1 slots and the nvme part of your m.2 connector. Again, useful if you have a m.2 SSD that can use SATA instead of pci-e lanes, and you'd prefer the slot to have all four lanes (for example for a 4K capture card, or for a 10..100gbps network card etc)

 

So if you're not using the M.2 connector, all the physical slots remain fully functional (if you decide to give each slot one lane) or the bottom pci-e x16 slot can have 4 pci-e lanes but the 3 pci-e x1 slots will be unusable.

If you decide to use the M.2 connector, any SSD you insert there would work with maximum 2 pci-e lanes worth of speed, or about 2 x 500 MB/s or 1 GB/s because that's all you have.

 

There are M.2 SSDs with SSD controller chips that can only use up to 2 pci-e lanes, like WD SN500 series, Adata SX6000, Corsair MP300 and others...

 

Your best option speed wise, would be to buy one of those adapter cards that I linked to, and install the M.2 SSD on it.

This way, your bottom pci-e x16 connector remains at pci-e x4 speeds, or 2 GB/s.

 

 

 

 

 

[keavlar]

21 minutes ago, mariushm said:

How do I know that red pci-e slots are coming from CPU?  From experience, from knowing about how hardware works

On most modern processors, you get 16 lanes or more from CPU which by default go to the video card slot, as the video card needs a lot of bandwidth.

Some chipsets allow those 16 lanes to be split into 2 groups of 8 lanes, and these separate groups can be wired to two separate slots. 

 

PCI Express is designed around the concept of PCI-E LANES ... each lane is a bi-directional channel of communication between a device and the host.

Also by design, there are some rules:

1. a device using pci-e MUST work with as little as a single pci-e lane to communicate with the computer.

2. the pci-e slot's physical size may indicate a number of pci-e lanes, but in reality only a certain number of pci-e lanes may be present inside the slot.

 

So you have to understand that the physical size of a pci-e slot (x16 , x4) does not always correlate with the number of pci-e lanes connected to that pci-e slot.

 

The M.2 connector is just a fancy right angle SLOT (that's very low height) which has a mix of pins:

* most of the contacts/pins that would be in a physical pci-e x4 slot  (the 4 pci-e lanes wires, plus 3.3v, but no 12v)

* some pins that carry the signal you would have in a SATA cable (cheaper SSD drives can use the classic SATA protocol)

* other pins that are outside the scope of this explanation.

 

A motherboard manufacturer is free to do what it wants. He can connect

* just the SATA part of the M.2 connector, in which case you can only use SATA SSDs with that connector, or

* he can only connect one or more pci-e lanes to the connector in which you say it's a nvme only M.2 connector,

* he can connect both pci-e lane(s) AND the SATA part, in which case you can use any kind of SSD

 

Also, as I explained above, the manufacturer is free to wire as little as one pci-e lane, or two pci-e lanes, or the maximum number of 4 pci-e lanes to the M.2 connector. It's a maximum of 4 because that's how many actual physical contacts are reserved for pci-e lanes. Who knows, in the future there may be more lanes... there are some contacts in the m.2 connector that are currently not used for anything.

 

On your particular motherboard, Asus decided to take 2 pci-e lanes created by the chipset and connect them to your M.2 connector. No matter what SSD you would insert in the connector, you would 

If you install a pci-e x4 M.2 SSD in the connector, there's only 2 actual pci-e lanes wired to that connector, so the M.2 SSD will work with only 2 pci-e lanes, possibly at reduced speed.

 

Now, you have to picture the chipset like a network switch, with 8 or 16 or 24 ethernet connectors, but instead of ethernet connectors you have pci-e lanes.

Some of these pci-e lanes are used inside the chipset itself to connect SATA controllers, some are used for USB 3 hubs - the motherboard manufacturer can choose to enable more SATA ports and put more physical SATA ports on the motherboard by enabling a SATA controller inside the chipset, but then there's fewer pci-e lanes going outside the chip to slots. 

 

On your particular motherboard, Asus made some choices in regards to how many SATA and USB ports you have which resulted on having a reduced number of pci-e lanes available to be routed to slots.

In order to wire everything right, they would have needed at least 11 pci-e lanes:

* 4 pci-e lanes for the third pci-e x16 slot (electrical pci-e x4)

* 4 pci-e lanes for the M.2 connector

* 3 pci-e lanes for the 3 pci-e x1 slots

However, due to how they did everything on the motherboard, they had much fewer lanes to work with, so some pci-e lanes are wired to two things at the same time (a slot and the m.2 connector at same time for example).

 

They tell you how everything works on page 40 of the manual :

 

 

 

So basically, they're using 4 pci-e lanes from chipset to connect as much as 4 pci-e slots and a M.2 connector to the chipset, but not at the same time.

You have one option in the BIOS which has several options : Auto, pci-e x1 , M.2 , pci-e x4

 

On Auto, you have 2 options :

* if there's a card installed in one of the pci-e x1 slots, the motherboard makes all black pci-e slots x1, so the black pci-e x16 slot becomes x1 as well.

* if there's no cards installed in the pci-e x1 slots but there's a card in the black pci-e x16 slot, that slot gets 4 pci-e lanes.

 

On pci-e x1 mode,  you're forcing the motherboard to keep all four slots functional at x1.

This can be useful if you have an M.2 SSD which can "talk" to the computer using either nvme (pci-e lanes) or SATA - you're disabling the nvme part of the M.2 connector and you're forcing the M.2 SSD to talk using the SATA part, at lower speeds (ex around 550 MB/s max) 

 

On M.2 mode, you're reserving 2 lanes for the M.2 connector, and that leaves the black pci-e x16 slot with only two lanes, making it a pci-e x2 slot. The other pci-e x1 slots are disabled

 

On pci-e x4 mode, you're forcing all 4 lanes to stay in the black pci-e x16 slot, disabling the other pci-e x1 slots and the nvme part of your m.2 connector. Again, useful if you have a m.2 SSD that can use SATA instead of pci-e lanes, and you'd prefer the slot to have all four lanes (for example for a 4K capture card, or for a 10..100gbps network card etc)

 

So if you're not using the M.2 connector, all the physical slots remain fully functional (if you decide to give each slot one lane) or the bottom pci-e x16 slot can have 4 pci-e lanes but the 3 pci-e x1 slots will be unusable.

If you decide to use the M.2 connector, any SSD you insert there would work with maximum 2 pci-e lanes worth of speed, or about 2 x 500 MB/s or 1 GB/s because that's all you have.

 

There are M.2 SSDs with SSD controller chips that can only use up to 2 pci-e lanes, like WD SN500 series, Adata SX6000, Corsair MP300 and others...

 

Your best option speed wise, would be to buy one of those adapter cards that I linked to, and install the M.2 SSD on it.

This way, your bottom pci-e x16 connector remains at pci-e x4 speeds, or 2 GB/s.

 

 

 

 

 

Wow...  amazing. 

Thanks.

 

So allow me to summorize it. 

If i got it right.

For me to get best pergormance from GPU ans SSD, 

I should keep the gpu in the top slot. (First red 1)

And the  m.2 ssd slot keep clearn, and instead pale it to the last slot (black one)

And  while doing it, I wont be able to use it as Windows System boot ?!  

 

Did I got it right ?

 

[mariushm]

I don't know if the BIOS supports booting from the pci-e slots or not. It depends on motherboard and BIOS.

Basically, don't be surprised if it does not boot unless the SSD is in the m.2 connector.

 

 

[keavlar]

10 minutes ago, mariushm said:

I don't know if the BIOS supports booting from the pci-e slots or not. It depends on motherboard and BIOS.

Basically, don't be surprised if it does not boot unless the SSD is in the m.2 connector.

 

 

But i got it right? 

[mariushm]

Yes, for best performance without affecting video card performance, installing the M.2 SSD into an adapter card in the pci-e x4 (black x16) slot is best.

 

Even faster speeds would be installing M.2 in 2nd red slot, but you'll decrease the video card performance by a tiny bit this way.

Probably won't notice it in real life, but you'll also not notice the SSD being limited to 2 GB/s by the pci-e x4 slot.

[keavlar]

4 minutes ago, mariushm said:

Yes, for best performance without affecting video card performance, installing the M.2 SSD into an adapter card in the pci-e x4 (black x16) slot is best.

 

Even faster speeds would be installing M.2 in 2nd red slot, but you'll decrease the video card performance by a tiny bit this way.

Probably won't notice it in real life, but you'll also not notice the SSD being limited to 2 GB/s by the pci-e x4 slot.

Thankks mate

[keavlar]

30 minutes ago, mariushm said:

Yes, for best performance without affecting video card performance, installing the M.2 SSD into an adapter card in the pci-e x4 (black x16) slot is best.

 

Even faster speeds would be installing M.2 in 2nd red slot, but you'll decrease the video card performance by a tiny bit this way.

Probably won't notice it in real life, but you'll also not notice the SSD being limited to 2 GB/s by the pci-e x4 slot.

I have few other questions if i may

"" the first line : 1. PCIeX 4_3 slot runs at X1 mode. 

meaning like : 

PCI Express 1.0

2 Gbit/s (250 MB/s)

32 Gbit/s (4000 MB/s)

 

So X2 mode meaning 

PCI Express 2.0

4 Gbit/s (500 MB/s)

64 Gbit/s (8000 MB/s)    Correct ?

 

[mariushm]

No,  x1 and x2, the number after the X, refers to the number of lanes that are possible to be present in the physical connector/slot... 

 

You have pci-e version 2.0 (500 MB/s per lane) slots, the black ones, and you have pci-e version 3.0 slots (approx. 970 MB/s per lane), the red ones.

 

The M.2 connector uses pci-e version 2.0 lanes, coming from chipset. So you get max 2 x 500 MB/s in the M.2 connector.

 

[keavlar]

24 minutes ago, mariushm said:

number of lanes that are possible to be present in the physical connector/slot... 

Sorry, i dont think i get this

[mariushm]

Jesus, I went through this at least two times already.

 

Each pci-e slot can have one or more LANES.

A pci-e slot can have a physical size that's different than the number of actual LANES WIRED, or USED,  to that slot.

 

ex. You can have a pci-e x16 slot (as in 16 units long) on the motherboard, but inside it you could have only 1, 2, 4 or 8 actual lanes.

 

Here's an example:

 

 

The bottom pci-e slot has two valid names :

 

1. pci-e x16 physical - if you're thinking of it's length - it's long enough that you can plug x16 cards in it.

2. pci-e x4  electrical - if you're thinking of the number of actual LANES in the connector, those metal contacts inside the slot. You can see that only a tiny bit inside is populated with metal contacts.

 

Each of those LANES can transfer data at a particular speed, depending on the pci-e VERSION.

 

If you have pci-e version 1, then speed of each lane is 250 MB/s

If you have pci-e version 2, then speed of each lane is 2 x 250 = 500 MB/s

If you have pci-e version 3, then speed of each lane is ~970 MB/s

If you have pci-e version 4, then speed of each lane is 2 x ~970 = ~ 1940 MB/s

 

The maximum speed of a SLOT is equal to : number of ELECTRICAL LANES x LANE SPEED

 

The maximum speed of a device plugged into a slot is equal to number of electrical lanes actually used by device x lane speed - for example, if you plug a pci-e x1 network card into a x16 slot (electrical and physical), the network card will only use 1 pci-e lane, so will have a speed of 500 MB/s or 970 MB/s (depending on the pci-e version).

 

On your Asus motherboard, the bottom pci-e x16 slot has UP TO 4 pci-e lanes in it, depending on how you configure it from the BIOS.

No matter what, those lanes are pci-e version 2, which means the individual lanes have a speed of 500 MB/s each.

 

 

 

[keavlar]

6 minutes ago, mariushm said:

Jesus, I went through this at least two times already.

 

Each pci-e slot can have one or more LANES.

A pci-e slot can have a physical size that's different than the number of actual LANES WIRED, or USED,  to that slot.

 

ex. You can have a pci-e x16 slot (as in 16 units long) on the motherboard, but inside it you could have only 1, 2, 4 or 8 actual lanes.

 

Here's an example:

 

 

The bottom pci-e slot has two valid names :

 

1. pci-e x16 physical - if you're thinking of it's length - it's long enough that you can plug x16 cards in it.

2. pci-e x4  electrical - if you're thinking of the number of actual LANES in the connector, those metal contacts inside the slot. You can see that only a tiny bit inside is populated with metal contacts.

 

Each of those LANES can transfer data at a particular speed, depending on the pci-e VERSION.

 

If you have pci-e version 1, then speed of each lane is 250 MB/s

If you have pci-e version 2, then speed of each lane is 2 x 250 = 500 MB/s

If you have pci-e version 3, then speed of each lane is ~970 MB/s

If you have pci-e version 4, then speed of each lane is 2 x ~970 = ~ 1940 MB/s

 

The maximum speed of a SLOT is equal to : number of ELECTRICAL LANES x LANE SPEED

 

The maximum speed of a device plugged into a slot is equal to number of electrical lanes actually used by device x lane speed - for example, if you plug a pci-e x1 network card into a x16 slot (electrical and physical), the network card will only use 1 pci-e lane, so will have a speed of 500 MB/s or 970 MB/s (depending on the pci-e version).

 

On your Asus motherboard, the bottom pci-e x16 slot has UP TO 4 pci-e lanes in it, depending on how you configure it from the BIOS.

No matter what, those lanes are pci-e version 2, which means the individual lanes have a speed of 500 MB/s each.

 

 

 

Now i get it better .  thanks and sorry, it is all new for me, and english not my nativ language. Thats why in tech i need more physical exa,ple like this one .

Cheers mate

[keavlar]

On 10/18/2019 at 10:28 PM, mariushm said:

On your Asus motherboard, the bottom pci-e x16 slot has UP TO 4 pci-e lanes in it, depending on how you configure it from the BIOS.

No matter what, those lanes are pci-e version 2, which means the individual lanes have a speed of 500 MB/s each.

Sorrry to get back to this. So if i am correct after reading what you said. Cause it is x4 so it has 4 lanes = individual lanes have a speed of 500 MB/s each. *4 =2000MB/s ?

[mariushm]

Yes, because the individual lanes are pci-e version 2.0 (which means 500 MB/s) and because you have a maximum of 4 lanes in that slot, your maximum transfer speed is 4 x 500 MB/s = 2000 MB/s

 

[keavlar]

4 minutes ago, mariushm said:

Yes, because the individual lanes are pci-e version 2.0 (which means 500 MB/s) and because you have a maximum of 4 lanes in that slot, your maximum transfer speed is 4 x 500 MB/s = 2000 MB/s

 

And to know about how many electrical lanes in x16 slot. you can only by manual of the MB.  like this one, and not by the actual name like on the page i attached before?! 

  

 

 

 

The manual about modes, made me think in the wrong way  ..