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Old 24th Feb 2017, 17:30   #1
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Crossfire in an NCase M1?

I plan on my next PC being mini-itx and sff and so one of the top case contenders is the m1. I recently saw a thread on sff forums where someone was using an m.2 to PCI-E 3.0x4 adapter to have a dedicated gpu on a mini-stx build. Now as crossfire can run on x4 bandwidth, would it be possible to have 2x watercooled GPUs (most likely Vega 11) running in the 1st and 3rd slot on the case with one of them running off an m.2 slot on ideally an X300 motherboard with 2x M.2 to allow me to have an nvme ssd as well.

Is this possible, I am thinking that a dual gpu ncase m1 with something like an apogee drive II cpu block and a 240mm radiator would make a potent mini itx rig.

Edit: This is the adapter and I would be looking at getting a PCI-E riser cable to mount the gpu in the 3rd slot. Other one with a molex plug: here.
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Old 24th Mar 2017, 12:34   #2
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I have a Ncase M1 and I can tell you now that there is physically no room in the case for a second GPU even if you could get it to work of an M2 to PCI-E adapter.

Secondly at x4 even on PCI-E 3.0 you'll end up bottle necking the gpu as you won't have enough bandwidth on the lane to feed the card data fast enough and you'll see fps that worse that if you just had one card at x8 or x16.

(Source is experience, accidentally ran a x8 gen 3 lane at x4 gen 3 and my fps tanked super hard.)

My advice would be to get a mATX board if you wanna run dual gpu's as the often support x8 gen 3 on two lanes. A good alternative case that would fit an mATX board and still be very compact is the Cerberus. Its got the same kind of philosophy behind it as the M1, max space efficiency without unnecessary compromise. Even had a similar backstory! Made by some people from a forum who banded together to make something unique.

Here's a link to their official forum thread where you can talk to other people who have the case and even ask the creators questions etc etc (Link)

Here's the official site for the case so you can quickly look at specs like dimensions etc. (Cerberus mATX case)

Hope this helps!
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Old 24th Mar 2017, 12:45   #3
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I've read around and on games that work well with crossfire then 2GPUs is better than one, having seen numerous mods of an ncase m1 with a 240mm radiator in the bottom with 25mm fans (occupying slot 3 and slot 2 in terms of space), I think another single slot gpu would easily fit in slot 3 with a short riser cable and m.2 adapter. If the game has naf crossfire support then I would just run off 1 card which is exactly what I currently do with my dual rx480s in a jonsbo rm1.

The Cerberus I have looked at before but at 18L and not in existence yet, it isn't all that much better than the mods I plan on my jonsbo. The reason for wanting to use the ncase m1 was the 3rd expansion slot allowing for a 2nd gpu running off m.2 on an applicable motherboard. I appreciate the 2nd card in cf will be slightly limited by the x4 bandwidth, but it is pci-e 3x4 (pci-e 2x16) so the difference isn't significant. Especially considering crossfire scales bettter than sli as a rule of thumb.

I intend on getting an ncase m1 and 1 card with a 240 rad on the side initially anyway. I was just trying to determine that if I got a motherboard with an additional full bandwidth m.2 slot, would I be able to add in another card for crossfire and then have crossfire running on games that support it at home while hooked up to additional cooling such as an alphacool eiswand. Then have a QDC setup so that for lans etc I can take the ncase and run as a single gpu.
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Old 24th Mar 2017, 16:04   #4
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Yes you can fit a radiator with slim fans below a gpu with a waterblock but here is the issue you'll have with two gpu's (see image)



The last slot in only there for 3 slot single gpu's. If you try to fit a 2nd gpu down there you'll have to cut off the half the IO port on the back (usually the half that has DVI on it) because there it no space for it to slot into.

Secondly I wouldn't advice using a single 240 to cool the cpu and both gpu's. That is a lot of wattage to dissipate of over a 240 and bare in mind you won't be using a super think rad as there isn't enough clearance for one AND regular 120mm fans. Which you'll need to use if you want to even think about cooling a single gpu with the cpu.

Not to sound like a shill pushing a product but the Cerberus is actually on sale now. They do it in batches so if you want one you need to state your interest on that thread. They'll add you to a list for the next batch iirc.

They've already shipped out a batch this January just gone so its not vapourware or just a concept.
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Old 24th Mar 2017, 18:02   #5
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Some mITX motherboards support PCIE bifurcation, so you can split a 16-lane slot into 2 8-lane slots with a suitable riser. There's no room in an M1 for two GPUs, though, even Nano or mini cards.

Gigabyte's two Z270 mITX boards definitely support bifurcation, and I believe AsRock boards do too.
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Old 24th Mar 2017, 18:16   #6
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Originally Posted by FatalSyntaxError View Post
Yes you can fit a radiator with slim fans below a gpu with a waterblock but here is the issue you'll have with two gpu's (see image)



The last slot in only there for 3 slot single gpu's. If you try to fit a 2nd gpu down there you'll have to cut off the half the IO port on the back (usually the half that has DVI on it) because there it no space for it to slot into.

Secondly I wouldn't advice using a single 240 to cool the cpu and both gpu's. That is a lot of wattage to dissipate of over a 240 and bare in mind you won't be using a super think rad as there isn't enough clearance for one AND regular 120mm fans. Which you'll need to use if you want to even think about cooling a single gpu with the cpu.

Not to sound like a shill pushing a product but the Cerberus is actually on sale now. They do it in batches so if you want one you need to state your interest on that thread. They'll add you to a list for the next batch iirc.

They've already shipped out a batch this January just gone so its not vapourware or just a concept.
As I said I have no interest in the cerberus for what is essentially 2L smaller than my current case and fits the same amount of components. Don't get me wrong the cerberus has a far better layout and requires little to no modding for what I plan but I already have a case for that project that I have invested in.

I would be buying a single slot bracket for whatever GPUs I use as there are several cards that have only 1 slot of inputs and the other is just a vent (reference rx480 or 1080ti for example).

I tried to explain above but my idea is that crossfire would only be used when hooked up to additional external cooling at home, then in 'portable mode' I would just have 1 gpu running, whether this is just leaving the 2nd gpu idle or actually unplugging it I haven't figured out yet. I have used tdp charts to work it out and with a oc'd r7 1700 and a flagship 250w card it suggests I would need 1.9 x 120mm radiators for a 10 degree C delta. The requirement is lower with a higer delta and if I were to add the other card I would in theory be adding another 360mm external radiator with pumps to match (if I go with the eiswand), so I believe the dual scenario cooling isn't the issue.

My concern was really the electrical side of things in that would crossfire work using an m.2 adapter. As far as measurements go I am fairly confident 2 single slot waterblocks in slot 1 and 3 with a side rad would fit.

Quote:
Originally Posted by bawjaws View Post
Some mITX motherboards support PCIE bifurcation, so you can split a 16-lane slot into 2 8-lane slots with a suitable riser. There's no room in an M1 for two GPUs, though, even Nano or mini cards.

Gigabyte's two Z270 mITX boards definitely support bifurcation, and I believe AsRock boards do too.
I had also considered this but from what I've read it is hit and miss on whether it works and I would ideally be putting my r7 1700 in this case so would be looking at a currently mythical x300 motherboard. I was assuming that 2xM.2 was more likely than supporting bifurcation but I could be wrong.


EDIT:

In my situation, I am only ever using crossfire while I add an external loop with QDCs at home. I am thinking that the 2nd card could just have QDCs and be on a separate external loop. It would mean it is completely independent and won't contribute to the initial loop while I run 1 card and then when 'docked' It can crossfire. This is also taking into account that when disconnected I would be using 1 screen where as at home it would be 3.
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Last edited by atc95; 24th Mar 2017 at 20:05.
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Old 25th Mar 2017, 12:50   #7
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Okay, I can understand what you're trying to better now. I theory it could work but as I mentioned before pcie x4 gen 3 isn't going to provide sufficient bandwidth for the second card to run well. You'll see performance will be worse than having just a single card not because crossfire doesn't scale well in those games but because the 2nd gpu will be bottle necking the entire system.

PCIE x4 gen 3 isn't equivalent to PCIE x16 gen 2. PCIE gen 3 doubled the bandwidth at each multiplier so in effect what you got was as follow:

PCIE x16 Gen 3 = PCIE x32 Gen 2 (this isn't a real slot but just illustrates how much bandwidth a x16 Gen 3 slot has.)

PCIE x8 Gen 3 = PCIE x16 Gen 2

PCIE x4 Gen 3 = PCIE x8 Gen 2

PCIE x2 Gen 3 = PCIE x4 Gen 2

This is why you can Crossfire/SLI using two x8 Gen 3 lanes because they both provide the same amount of bandwidth as a x16 Gen 2 lane did, which is what you used to need to go Crossfire/SLI previously when Gen 2 was the latest PCIE standard.

You're x4 Gen 3 lane is only equivalent to an x8 Gen 2 PCIE lane, this that second GPU will not be feed data fast enough and so the whole crossfire system gets bogged down because your 1st GPU running off a x16/x8 Gen 3 lane is waiting for the second gpu to first be feed data then number crunch it.

I know this from experience as I accidentally switched the lane that my second gpu in my SLI setup was running in to a x4 gen 3 protocol in the bios and my frame rates tanked horrible. I thought that one of my GPU's had developed a hardware issue at one point until testing them individually confirmed they both worked just fine.

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Old 25th Mar 2017, 13:55   #8
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Okay, I can understand what you're trying to better now. I theory it could work but as I mentioned before pcie x4 gen 3 isn't going to provide sufficient bandwidth for the second card to run well. You'll see performance will be worse than having just a single card not because crossfire doesn't scale well in those games but because the 2nd gpu will be bottle necking the entire system.

PCIE x4 gen 3 isn't equivalent to PCIE x16 gen 2. PCIE gen 3 doubled the bandwidth at each multiplier so in effect what you got was as follow:

PCIE x16 Gen 3 = PCIE x32 Gen 2 (this isn't a real slot but just illustrates how much bandwidth a x16 Gen 3 slot has.)

PCIE x8 Gen 3 = PCIE x16 Gen 2

PCIE x4 Gen 3 = PCIE x8 Gen 2

PCIE x2 Gen 3 = PCIE x4 Gen 2

This is why you can Crossfire/SLI using two x8 Gen 3 lanes because they both provide the same amount of bandwidth as a x16 Gen 2 lane did, which is what you used to need to go Crossfire/SLI previously when Gen 2 was the latest PCIE standard.

You're x4 Gen 3 lane is only equivalent to an x8 Gen 2 PCIE lane, this that second GPU will not be feed data fast enough and so the whole crossfire system gets bogged down because your 1st GPU running off a x16/x8 Gen 3 lane is waiting for the second gpu to first be feed data then number crunch it.

I know this from experience as I accidentally switched the lane that my second gpu in my SLI setup was running in to a x4 gen 3 protocol in the bios and my frame rates tanked horrible. I thought that one of my GPU's had developed a hardware issue at one point until testing them individually confirmed they both worked just fine.
SLI does require x8 x8 though as a minimum whereas crossfire can run at x8 x4 from what I understand. In my case it would be x16 and x4 so yes the 2nd card would be getting ľ of the bandwidth, but reading online suggests cards donít need x16 anyway and I am thinking that the benefit of 2 cards in supported titles will outweigh the bandwidth limitation the 2nd card brings as a bottleneck. Then for any game that is better on a single gpu, I can just disable crossfire and the 1st card (most likely vega) should be able to run 1440p fine or ideally 4320x1278 (I have a poor mans eyefinity setup).
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Old 25th Mar 2017, 14:25   #9
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From what I have been told recently by TTL @ OC3D AMD now require X8. I don't know how true that is, and would still read into it, but yeah bear it in mind.

I also wouldn't touch Crossfire with a 200ft pole.
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Old 25th Mar 2017, 14:26   #10
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From what I have been told recently by TTL @ OC3D AMD now require X8. I don't know how true that is, and would still read into it, but yeah bear it in mind.

I also wouldn't touch Crossfire with a 200ft pole.
Will look into it then, I am running cf on the rx480s and for me it is either a 70-80% boost or about 5-10% worse than normal so just disable on a per game basis.
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Old 25th Mar 2017, 14:50   #11
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FYI, here's a thread from [H] about PCIE bifurcation: the post linked here shows a chap who's managed to fit 2 R9 Nanos into his Dan A4. Food for thought?
https://hardforum.com/threads/pcie-b...ost-1042880213

Personally, I'd just go for the fastest possible single card solution
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Old 25th Mar 2017, 16:22   #12
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Will look into it then, I am running cf on the rx480s and for me it is either a 70-80% boost or about 5-10% worse than normal so just disable on a per game basis.
Oh OK well if you are happy with it then that's cool It drove me round the frikkin bend when I had two Fury X.
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Old 25th Mar 2017, 16:49   #13
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FYI, here's a thread from [H] about PCIE bifurcation: the post linked here shows a chap who's managed to fit 2 R9 Nanos into his Dan A4. Food for thought?
https://hardforum.com/threads/pcie-b...ost-1042880213
That much heat packed so dense? I hope he got some ear plugs on standby when that thing turns on.

Personally I wouldn't bother and just get a readily available case that easily fits the hardware, like for example the Fractal Design Node 804.
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Old 25th Mar 2017, 21:00   #14
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Old 26th Mar 2017, 15:03   #15
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SLI does require x8 x8 though as a minimum whereas crossfire can run at x8 x4 from what I understand. In my case it would be x16 and x4 so yes the 2nd card would be getting ľ of the bandwidth, but reading online suggests cards donít need x16 anyway and I am thinking that the benefit of 2 cards in supported titles will outweigh the bandwidth limitation the 2nd card brings as a bottleneck. Then for any game that is better on a single gpu, I can just disable crossfire and the 1st card (most likely vega) should be able to run 1440p fine or ideally 4320x1278 (I have a poor mans eyefinity setup).
I think you're misunderstanding the technical issue I'm trying to get across to you, its not about whether the game utilities CF well or not and that if it does it'll overcome the bandwidth issue.

Lets say you have a game that takes advantage of CF in the perfect best case senario where the second card is giving you 100% scaling in terms of FPS gain over a single card.

Game X, with graphic settings at high, gives you 60 fps on one card and in CF you get 120 FPS at the same settings. This while running both cards in PCIE x8 (gen 3) lanes.

If you now take the same game (Game x) and run at the exact same settings (high) in CF with one card in a, lets say for arguments, sake PCIE x8 (gen 3) and the second card in a PCIE x4 (gen 3) lane, you will now gets 45 fps.

As you can see in the second scenario your CF setup is giving worse frame rates than a single card. This is because that second card in the second scenario can not be fed data fast enough for it to output frames at its maximum capable speed. Because of this, the overall CF setup is now performing far worse.

CF/SLI is only as good as the slowest card in the system so running the second rx480 in an PCIE x4 (gen 3) lane is like you under clocked the card so it always ran at half its core speed. The entire CF system is waiting for that second gpu to get its job done which means it can only be as fast as that second gpu can throw out frames.

I hope I've managed to illustrate my point a bit better now I'm by no means saying don't try to get two gpu's into a Ncase M1, after all we're on a modding forum, and I for one would love to see an SLI/CF setup in an Ncase M1. The issue is trying to run that second GPU of the M2 PCIE lanes. They just don't have the bandwidth.

However if you try to do something similar to what the guy with the Dan case did and bifurcate an x16 (gen 3) lane of the ITX board into two x8 (gen 3) lanes then it does seem possible from a technical standpoint. I'm not sure how two GPU's sharing data transmission through the same PCIE slot would effect CF in terms of interference and noise between one another or if that would even be an issue.

Anyone with an understand on electrical circuit design etc want to chime in on that?

Hope I helped and if you go through with it be sure to keep us updated!
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Old 26th Mar 2017, 19:05   #16
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I think you're misunderstanding the technical issue I'm trying to get across to you, its not about whether the game utilities CF well or not and that if it does it'll overcome the bandwidth issue.

...

Anyone with an understand on electrical circuit design etc want to chime in on that?

Hope I helped and if you go through with it be sure to keep us updated!
I completely see your point but from what I have read I don't believe it is as linear a relationship as half bandwidth is half the frame rate. Based off this albeit old article it is more like a 10-15% drop in frames from 3.0 x16 to 2.0x4. On that basis crossfire with perfect scaling would be more like 100fps rather than the 45 your scenario suggests. I agree that the limited bandwith has a performance penalty, but even with say only 60% scaling, it would be a decent boost over a single card. The price/performance isn't great but this is as you said, a modding forum, and I think dual gpus in an ncase is worth it!

EDIT: A more recent version of the same article uses a gtx 1080 and at 4K and 1440p respectively, the performance difference between pci-e3.0 x4 via the chipset (aka m.2 adapter) and pcie3.0x16 is 5% and 7% respectively.
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Old 27th Mar 2017, 00:09   #17
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Half frame rate was just an example in that scenario I was describing, that's an interesting article you linked to there. I ended up gimping my SLI setup when I ran one of my cards on a slower bandwidth lane.

In that article they seem only be testing a single card in each slot type, so not sure if it'll translate the same in CF but hey, worse case scenario, you just split the x16 lane on the ITX board into two x8 lanes using a splitter like in the Dan case example.

Be sure to drop me a PM with your official mod thread once you get started, of course I'll keep an eye out for any Ncase M1 mods in case its yours.

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Old 27th Mar 2017, 09:31   #18
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Quote:
Originally Posted by FatalSyntaxError View Post
Half frame rate was just an example in that scenario I was describing, that's an interesting article you linked to there. I ended up gimping my SLI setup when I ran one of my cards on a slower bandwidth lane.

In that article they seem only be testing a single card in each slot type, so sure if it'll translate the same in CF but hey, worse case scenario, you just split the x16 lane on the ITX board into two x8 lanes using a splitter like in the Dan case example.

Be sure to drop me a PM with your official mod thread once you get started, of course I'll keep an eye out for any Ncase M1 mods in case its yours.
I'll look up some more examples of the different PCI-E bandwidths. The plan as it stands is to get the first vega card and an x300 itx mobo and then add a 2nd card to the loop or an external loop after a couple of months. I am hoping to get the project underway around June/July.
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