pcie layout of Ryzen motherboards question.

[William Gaatjes]

Hi, i am researching what components to buy for my big upgrade. The cpu being more of a soc, has several pci-e connections.
16 lanes are for the graphics. But there are several pci-e lanes left as is the m2 ssd pci-e lanes and sata signals.
I want the lowest latency, so the best way is to connect the ssd to the cpu directly. Bypassing the motherboard chipset. The on board connection for the ssd m2 seems best but...
I noticed that a lot of boards have the m2 ssd located closely above or under the gpu card.
That would limit the possibility to cool the m2 ssd with an external cooling solution such as for example a passive heatsink. And when playing a game, the m2 ssd would heat up because of the graphics card dumping heat on the m2 ssd. I wonder why so much motherboard manufacturers have chosen to stick the m2 ssd so close to the graphics card. The max tracelength for pci-e signals seem to be 12 inch(30 cm). Lot of room to place that m2 ssd somewhere else. But i am not certain if that lenght is also correct for pci-e gen2 and gen3.
If anybody knows, i am all interested.

The m2 ssd option seems best, but i want to stick a heatsink on it.

I was thinking that one possible solution may be to buy an pci-e ssd instead.
And stick that in a free pci-e slot.
But i do not want the graphic card do switch back from x16 to x8 when going for this solution.
Or that the pci-s card would be connected to the chipset instead of directly to the cpu.

Example :

I am wondering where to get the proper pci-e connections for the motherboard. Any body know where to find this ?



What i am also wondering about:
Has anyone ever done any tests what the difference is in latency with the m2 ssd directly connected to the cpu and when connecting the m2 ssd via the chipset ?
I have seen some boards with 2 m2 ssd connections.

Right now i am thinking of this motherboard but it is not set in stone yet:

 

[Insert_Nickname]

The m2 ssd option seems best, but i want to stick a heatsink on it.

Why? There is no need. Unfortunately there are a lot of myths floating around about M.2 and cooling.

If you're doing a lot of write intensive stuff, just make sure there is sufficient airflow around the M.2 slot.

As for buying an Intel 750, that is complete and utter overkill for home desktop use.

 

[William Gaatjes]

Why? There is no need. Unfortunately there are a lot of myths floating around about M.2 and cooling.

If you're doing a lot of write intensive stuff, just make sure there is sufficient airflow around the M.2 slot.

Interesting.
This is indeed mainly about writing. Which i would not be doing a lot during game play.
http://www.anandtech.com/show/9856/angelbird-wings-px1-m2-adapter-review-do-ssds-need-heatsinks/8
But i like my m2 ssd as cool as possible.
And with the m2 slot behind the graphics card the airflow might get restricted, or the m2 drive gets hot air from the gpu blown upon it.

Another option would be choosing the ASROCK instead of the gigabyte since here the m2 drive is located above the gpu and away from the heatsink of the gpu :
ASRock AB350 Pro4 : Is this a good quality board ?

I am thinking of a 960 pro 512GB from Samsung.
I still have zalman heatsinks laying around: I can stick those on.
They are low profile.
It is just that i like my system as cool as possible within for me reasonable limits.

As for buying an Intel 750, that is complete and utter overkill for home desktop use.

The intel was an example suggestion, but no longer relevant.
Sticking it into the second pci-e x16 slot that was meant for graphics would force the gpu card in the highest pci-ex16 slot to x8.
Sticking it in the lower pci-e slots, that would not fit as it seems.
Even if it did, it would connected through the chipset.
pci-e ssd is not an option anymore.


edit:
If i may believe the anandtech review for the 960 pro, writing consumes as much current as when reading.Even less. Which does seem strange.

http://www.anandtech.com/show/10754/samsung-960-pro-ssd-review

 

[Insert_Nickname]

Interesting.
This is indeed mainly about writing. Which i would not be doing a lot during game play.
http://www.anandtech.com/show/9856/angelbird-wings-px1-m2-adapter-review-do-ssds-need-heatsinks/8
But i like my m2 ssd as cool as possible.
And with the m2 slot behind the graphics card the airflow might get restricted, or the m2 drive gets hot air from the gpu blown upon it.

I'm running a simple 512GB Intel 600p in an ASUS Crosshair VI. I haven't seen temperatures above 65C during full-speed writes, which I'd consider reasonable. Idle is around 40C. To be fair there is a 120mm fan directly in front.

Another option would be choosing the ASROCK instead of the gigabyte since here the m2 drive is located above the gpu and away from the heatsink of the gpu :
ASRock AB350 Pro4 : Is this a good quality board ?

Asrock is usually good. They also tend to give a fair amount of features/$, and in some cases features you can't get anywhere else.

I am thinking of a 960 pro 512GB from Samsung.
I still have zalman heatsinks laying around: I can stick those on.
They are low profile.
It is just that i like my system as cool as possible within for me reasonable limits.

Hey, I remember those. It might not be a bad idea to put one one the controller, but beware of accidentally adding thermal conductivity.

The intel was an example suggestion, but no longer relevant.
Sticking it into the second pci-e x16 slot that was meant for graphics would force the gpu card in the highest pci-ex16 slot to x8.
Sticking it in the lower pci-e slots, that would not fit as it seems.
Even if it did, it would connected through the chipset.
pci-e ssd is not an option anymore.


edit:
If i may believe the anandtech review for the 960 pro, writing consumes as much current as when reading.Even less. Which does seem strange.

http://www.anandtech.com/show/10754/samsung-960-pro-ssd-review

Okay, lets take them one at the time:

1. Yes, it would force the primary PCIe slot into x8 mode. That said, I've run such a configuration for almost 3 years, and I've not noticed any significant performance penalty.
2. If connected to the chipset, you are dropping to PCIe 2.0 x4, with a maximum of ~1600MB/s transfer either way. Not recommended.
3. The controller might have to work harder reading at top speed, write speeds are quite a bit lower. So that might explain.

 

[wildhorse2k]

Avoid motherboards with M.2 directly below the main GPU slot.

Some motherboards like ASRock Taichi, or Asus Crosshair 6 Hero have M.2 in good location. M.2 attached to chipset is not the Ultra M.2 variant on X370, it is slower. M.2 should be connected only directly to CPU through PCIe.

Some cases allow to mount motherboard horizontally not vertically.

 

[William Gaatjes]

I'm running a simple 512GB Intel 600p in an ASUS Crosshair VI. I haven't seen temperatures above 65C during full-speed writes, which I'd consider reasonable. Idle is around 40C. To be fair there is a 120mm fan directly in front.

And the Crosshair, has the m2 ssd connector way in the right lower corner.
That is a great spot for a nvme drive.

The boards i am looking at have the connector either behind the graphics card or above.
I have to see if there are more options.
I prefer gigabyte because of the reliability i am used to. And gigabyte MB have standard dual bios. If anything goes wrong during bios updates, it is a matter of trying again.

Okay, lets take them one at the time:

1. Yes, it would force the primary PCIe slot into x8 mode. That said, I've run such a configuration for almost 3 years, and I've not noticed any significant performance penalty.
2. If connected to the chipset, you are dropping to PCIe 2.0 x4, with a maximum of ~1600MB/s transfer either way. Not recommended.
3. The controller might have to work harder reading at top speed, write speeds are quite a bit lower. So that might explain.

2.Aha, chipset connection is not an option indeed.
3.That makes sense, I do wonder, the flash chips usually have some internal high voltage generator to erase the flash pages. With smaller chips of a few megabits, the chip usually draws more current when it is erasing. It makes sense this is still the case. But, perhaps even when the flashchip is performing an erase and consuming a little more than when reading, the total power consumption is offset by the power consumption of the controller on board of the drive.
edit:
Also, there are delays when writing to flash. The controller may just be waiting more for the writes to complete per page if it cannot do writes in parallel or in a ping pong fashion.

 

[William Gaatjes]

Avoid motherboards with M.2 directly below the main GPU slot.

Yeah, this might be the main reason why i would not go for a Gigabyte motherboard this time.
All the Gigabyte motherboards i have seen so far have the m2 connector behind the gpu card just below the primary pci-e x16 clot.
I am worried that a graphic card with a larger than normal heatsink might interfere physically with the m2 card.
In the very least, i would not be able to stick on some heatsinks on the m2 drive.

Some motherboards like ASRock Taichi, or Asus Crosshair 6 Hero have M.2 in good location. M.2 attached to chipset is not the Ultra M.2 variant on X370, it is slower. M.2 should be connected only directly to CPU through PCIe.

Some cases allow to mount motherboard horizontally not vertically.

Yep, that is my desire too. the drive connected directly to the cpu.

 

[Elixer]

You may be interested in these articles about M.2 slot location & results.
https://www.pugetsystems.com/labs/articles/Samsung-950-Pro-M-2-Throttling-Analysis-776/
&
https://www.pugetsystems.com/labs/articles/Samsung-950-Pro-M-2-Additional-Cooling-Testing-795/

 

[William Gaatjes]

You may be interested in these articles about M.2 slot location & results.
https://www.pugetsystems.com/labs/articles/Samsung-950-Pro-M-2-Throttling-Analysis-776/
&
https://www.pugetsystems.com/labs/articles/Samsung-950-Pro-M-2-Additional-Cooling-Testing-795/

Interesting.
Are there also such articles on the 960 pro ?
I read that the 960 pro has improved throttle behavior over the 950. But that is only because to put a sticker on the underside with a copper layer embedded in it.

http://www.anandtech.com/show/10754/samsung-960-pro-ssd-review

Anyway, the high read speed would drop when gaming for a few minutes with a gpu fully active.
Loading levels would theoretically be slower, but by how much i do not know.

 

[Elixer]

Because it is so fast, I don't see any game doing sustained reads/writes to the SSD for more than a few secs, so, it is highly doubtful it would start to throttle with such little activity.

Overall, case cooling is where your should be looking at, if that is good, you shouldn't have any issues.

 

[UsandThem]

Interesting.
Are there also such articles on the 960 pro ?
I read that the 960 pro has improved throttle behavior over the 950. But that is only because to put a sticker on the underside with a copper layer embedded in it.

http://www.anandtech.com/show/10754/samsung-960-pro-ssd-review

Anyway, the high read speed would drop when gaming for a few minutes with a gpu fully active.
Loading levels would theoretically be slower, but by how much i do not know.

Get a Kyro M.2 card for $30, and never worry about the temps or the M.2 location.

https://forums.anandtech.com/thread...le-normal-for-nvme-ssd.2497459/#post-38704055

 

[William Gaatjes]

What is interesting with the asrock AB350 Pro4 is that the m2_1 socket (the ultra socket) share pcie lanes with the second graphic card slot(PCIE4).
If either is used, the other cannot be used. For me this is not an issue because i prefer single gpu set-ups.

The same goes for the second m2 ssd (nvme) slot. When the second m2 slot is used, the sata lines from nearby sata 3 connector are no longer usable. And vice versa.
The first m2 slot is pcie. The second m2 slot is sata3 6gbps.

I always have understood that pci-e and sata signals are point to point signals. I guess there is some high speed data multiplexer on the mainboard that reroutes the
signals over different traces.

 

[William Gaatjes]

Get a Kyro M.2 card for $30, and never worry about the temps or the M.2 location.

https://forums.anandtech.com/thread...le-normal-for-nvme-ssd.2497459/#post-38704055

That might be usable with the asrock AB350 Pro4.
The 16 lanes of the top pci-e slot are not divided in 8x for the top slot(PCIE2) and 8x for the bottom slot(PCIE4) when the bottom slot is used.
The ultra m2 nvme signals are available on this slot(PCIE4) as well.
(Yeah, i am reading the manual)
Forgot to mention, pci-e generation 3 32gbps.

Better yet, i will have to see if the gigabyte board has a similar pcie lanes setup.
edit:
nope, the second x16 size pcie slot only has pcie gen2 on the gigabyte GA-AB350-Gaming (rev. 1.0) board.
Both boards have their advantages depending on the user.

 

[William Gaatjes]

Because it is so fast, I don't see any game doing sustained reads/writes to the SSD for more than a few secs, so, it is highly doubtful it would start to throttle with such little activity.

Overall, case cooling is where your should be looking at, if that is good, you shouldn't have any issues.

I have 2 x 120mm case fans blowing at all time cool air in and one fan to suck the air out. That should be possible.

 

[wildhorse2k]

In a good motherboard Ultra M.2 shouldn't share PCIe lanes with the 2 graphics card PCIe slots. On some motherboards you may have 2nd M.2 (slower one) that uses PCIe lanes reserved for SATA. But who cares about SATA.

ASRock probably has the best M.2 placement from all motherboard makers for Z270, X370 and X99. They were also correct when they included M.2 on their motherboards in the past while other makers included the useless U.2. They also got the placement right and their boards have the best VRM and ok OC BIOS.

M.2 next to RAM perpendicular to motherboard could interfere with hard drives/optical drive. It's probably best to put it above graphic card slot and put a huge heatsink on it. Asus Crosshair 6 Hero should also work fine as long as you don't use SLI.

I considered buying Z270, X99 or X370 so I went through lot of manuals. For X370 Fatal1ty X370 Professional Gaming was my favorite (slightly more feature rich Taichi if you don't mind the price) due to best VRM, good PCIe slot placement, good M.2 placement, 5GBit LAN (1GBit is garbage these days). Asus Crosshair 6 Hero was 2nd.