SLI and M.2

Highlands · 3 Jan 2018 at 19:44

Hello everyone, hope your new year is off to a great start.

Last year my SSD decided to die, so I upgraded to an M.2 SSD. My only concern is that because my rig is running SLI 980ti's, I'm not getting the speeds which I should be expecting.

My knowledge regarding motherboards and their abilities is relatively limited. Could someone please let me know whether the following components may be causing a bottleneck, or restricting the slot speeds?

Motherboard: Asus Strix X99 Gaming Intel X99
CPU: i7 5820k
SSD: M.2. Samsung 950 Pro 256GB
GPU: SLI 980Ti

If this is causing an issue, would you recommend changing my SSD to an ordinary one?

Thank you very much for any advice in advance.

Minstadave · 3 Jan 2018 at 20:43

IIRC a 5820K has 28 PCI-E lanes.

Your SLI setup would use 32 lanes if it could, plus another 4 for your M2 drive. So you won't be getting full speeds somewhere.

Samsung magician will tell you what speed your SSD is running at and GPU-Z will tell you what bandwidth the GPUs have available.

SLI running at 2x8 rather than 2x16 won't make more than a slight difference.

4K8KW10 · 3 Jan 2018 at 20:46

@Highlands What speeds do you achieve? The advertised by Samsung are:

Sequential ReadUp to 2,200 MB/sec *Performance may vary based on system hardware & configuration
Sequential WriteUp to 900 MB/sec *Performance may vary based on system hardware & configuration
Random Read (4 KB, QD32)Up to 270,000 IOPS (Thread 4) *Performance may vary based on system hardware & configuration
Random Write (4KB, QD32)Up to 85,000 IOPS (Thread 4) *Performance may vary based on system hardware & configuration
Random Read (4 KB, QD1)Up to 11,000 IOPS (Thread 1) *Performance may vary based on system hardware & configuration
Random Write (4 KB, QD1)Up to 43,000 IOPS (Thread 1) *Performance may vary based on system hardware & configuration

http://www.samsung.com/uk/memory-storage/950-pro-nvme-m-2-ssd/MZ-V5P256BW/

My advice to you would be to get rid of the SLI and buy one graphics card that is as fast or faster.

CapitalOne · 3 Jan 2018 at 20:48

Minstadave said:
IIRC a 5820K has 28 PCI-E lanes.

Your SLI setup would use 32 lanes if it could, plus another 4 for your M2 drive. So you won't be getting full speeds somewhere.

Samsung magician will tell you what speed your SSD is running at and GPU-Z will tell you what bandwidth the GPUs have available.

SLI running at 2x8 rather than 2x16 won't make more than a slight difference.

Exactly this, or get a 40 lane CPU like a 6850k.

4K8KW10 · 3 Jan 2018 at 20:49

Doesn't SLI automatically switch to x8 + x8 configuration, though?

CapitalOne · 3 Jan 2018 at 21:02

4K8KW10 said:
Doesn't SLI automatically switch to x8 + x8 configuration, though?

Depends on the boardand slots I think, 3x SLI definately does drop to 16 16 8. I’ve actually got the Strix X99 with 2 TXM and an M2 samsung and I’m sure it’s 16 16 although as stated above I’m not sure it mateers too much.

Safetytrousers · 3 Jan 2018 at 21:46

I did a quick test of the difference between 8 and 16 lanes on a GTX 1080 in Valley benchmark and there was effectively no difference in the result at all (except for a tiny difference within the normal run to run variance).

Minstadave · 3 Jan 2018 at 22:33

4K8KW10 said:
@Highlands What speeds do you achieve? The advertised by Samsung are:

Sequential ReadUp to 2,200 MB/sec *Performance may vary based on system hardware & configuration

Sequential WriteUp to 900 MB/sec *Performance may vary based on system hardware & configuration

Random Read (4 KB, QD32)Up to 270,000 IOPS (Thread 4) *Performance may vary based on system hardware & configuration

Random Write (4KB, QD32)Up to 85,000 IOPS (Thread 4) *Performance may vary based on system hardware & configuration

Random Read (4 KB, QD1)Up to 11,000 IOPS (Thread 1) *Performance may vary based on system hardware & configuration

Random Write (4 KB, QD1)Up to 43,000 IOPS (Thread 1) *Performance may vary based on system hardware & configuration

http://www.samsung.com/uk/memory-storage/950-pro-nvme-m-2-ssd/MZ-V5P256BW/

My advice to you would be to get rid of the SLI and buy one graphics card that is as fast or faster.

If SSD speed is low it's worth checking via Samsung Magician what speed the link is running, my X99 board needs specific BIOS settings and card arrangement for the M2 slot to run at full PCI-E speeds.

Highlands · 4 Jan 2018 at 01:45

Thank you for the replies. I will check the speeds using magician and the bandwidths on GPU-Z tomorrow.

Overall though, I’m gathering that it’s not expected to make a detrimental difference in the performance.

Minstadave · 4 Jan 2018 at 12:51

Highlands said:
Thank you for the replies. I will check the speeds using magician and the bandwidths on GPU-Z tomorrow.

Overall though, I’m gathering that it’s not expected to make a detrimental difference in the performance.

It should be fine, run the GPUs 8x8x in SLI and make sure your SSD is configured to 4x and you’re sorted.