Parallel loop?

Dirk Diggler · 6 Mar 2015 at 16:43

See attached photo of current set-up. One 980 under water, and one on air. I'll be fitting a block on the bottom card soon, and for ease I could simply take a straight tube from each blanked off port on the top card, and connect to the bottom just like I've shown in the second picture.

Will this work?

I could also re-route the Res return via the bottom GPU to keep everything in series, but I really don't think it'll look as good?

Drangueos · 6 Mar 2015 at 16:49

Short answer: Yes

Dirk Diggler · 6 Mar 2015 at 17:09

Drangueos said:
Short answer: Yes

Sweet.

Dirk Diggler · 31 Mar 2015 at 22:14

For anyone interested, I added the second card as per the image (parallel) and they both sit at the exact same temperature. A couple of degrees above ambient when idle, and maybe around 45 degrees during heavy gaming sesh.

Perfect!

Cerelia · 31 Mar 2015 at 23:37

Sorry to burst your bubble but the fluid dynamics means the second card would see next to no flow in that setup. You need it in a Z pattern so the distance in the loop for each card is equal.

Going on the pictures you've posted.

You've the inlet on the 1st card on the top-right, so you would need the exit on the 2nd card to be on the bottom-left. With either bitspower white rotary or monsoon though you could do it with minimal changes to your loop.

Dirk Diggler · 1 Apr 2015 at 08:16

You're not bursting my bubble mate, I'm happy to get it right.

So, how come my second card isn't getting hotter than my first?

ErikN · 1 Apr 2015 at 08:38

Cerelia said:
Sorry to burst your bubble but the fluid dynamics means the second card would see next to no flow in that setup. You need it in a Z pattern so the distance in the loop for each card is equal.

Going on the pictures you've posted.

You've the inlet on the 1st card on the top-right, so you would need the exit on the 2nd card to be on the bottom-left. With either bitspower white rotary or monsoon though you could do it with minimal changes to your loop.

This is incorrect, according to EK waterblocks installation manuals for their parallell bridges, which would be the same as your connection:
http://www.ekwb.com/shop/EK-IM/EK-IM-3831109868065.pdf

Also, you can check the 8pack build in this forum, which is doing exactly this, but with four cards instead of two:
http://forums.overclockers.co.uk/showthread.php?t=18662538

Dirk Diggler · 1 Apr 2015 at 10:15

Here's the graph for idle...

And here's the graph for full load...

As you can see, they are literally +/- 1C.

Here's the full size images...

....

Dirk Diggler · 1 Apr 2015 at 11:32

Here's the setup, just for reference. The tube on the bottom right can be ignored, as it goes to a blank end (drain port).

ubersonic · 1 Apr 2015 at 12:09

String said:
So, how come my second card isn't getting hotter than my first?

Your method of plumbing will cause the lower card to get less flow than the top card, the thing with flow however is it has diminishing returns. Once you have enough/optimum flow then more doesn't do anything, it appears that in your setup both cards have "enough", the fact the top card is going to be getting more simply means it's overkilled more.

Cerelia · 1 Apr 2015 at 12:11

Why isn't the stress Gpu's in prime 95 selected in the 'graph' shots? Curious.

Dirk Diggler · 1 Apr 2015 at 12:49

ubersonic said:
Your method of plumbing will cause the lower card to get less flow than the top card, the thing with flow however is it has diminishing returns. Once you have enough/optimum flow then more doesn't do anything, it appears that in your setup both cards have "enough", the fact the top card is going to be getting more simply means it's overkilled more.

I've turned my D5 speed setting down from 5 to 2, and they're still +/- 1C.

Dirk Diggler · 1 Apr 2015 at 13:08

Cerelia said:
Why isn't the stress Gpu's in prime 95 selected in the 'graph' shots? Curious.

That's not Prime95 it's Aida64. I'm stressing the GPUs in the full load graph by running Heaven in windowed mode. I don't use Aida's GPU stress facility as it just causes screen freezes.

AndoriAvalonia · 1 Apr 2015 at 18:01

ubersonic said:
Your method of plumbing will cause the lower card to get less flow than the top card, the thing with flow however is it has diminishing returns. Once you have enough/optimum flow then more doesn't do anything, it appears that in your setup both cards have "enough", the fact the top card is going to be getting more simply means it's overkilled more.

Surely the difference in flow will be minimal? To my simplistic mind the flow rate will be a function of resistance (likening it to current in parallel resistors in an electrical circuit) and the resistance of the 2 blocks is going to be roughly equal. The only difference will be the slight extra restriction of the connection to the 2nd card.

One question I have though... what is that connection that appears to come off the bottom of the 2nd card?

Dirk Diggler · 1 Apr 2015 at 18:42

AndoriAvalonia said:
One question I have though... what is that connection that appears to come off the bottom of the 2nd card?

It goes to a stop end through the back, for a drain port.

AndoriAvalonia · 1 Apr 2015 at 22:05

String said:
It goes to a stop end through the back, for a drain port.

Ah, I thought it might be something like that as I counted an odd number of connections going to the back.