SLI GPU blocks series vs parallel

[D3LTA9]

General opinion is that performance is relatively similar between the two configurations but parallel tends to be less restrictive. Also have had read some comments that series is better for 2 gpu's and parallel for 3+. 

 

Currently I have my 780's in parallel using hard pipe to link them but am experiencing temp fluctuations, in particular after stress testing or gaming my temps dont drop back to the normal idle temps(around 20-25 degrees). Bottom GPU is worse than the top.

 

Think I need to swap to in series or reconfigure the inlet/outlet of my gpu blocks but before I do just wondering if anyone else has had issues running two GPU's in parallel before?

 

 

[jakkuh_t]

I did a build for a guy once and we ran each GPU on a seperate loop, it was pretty crazy.

[Nineshadow]

Series is cheaper.

With a single pump in parallel it would become hard to get equal water flow.

[Najuno]

I´ve got a GTX780 TI 2 way SLI in serial. TBH it doesn´t make too much of a difference as long as you are using a good pump such as a variable D5 with the right dimensioned loop.

Have been thinking about serial or parallel but come to think I´d only go for a parallel with more than 2 cards.

[D3LTA9]

Thanks for the replies everyone. Should have stated I am using a d5 vario on setting 5 (4800rpm) as a pump so should have plenty enough pumping power for 120.5 rad(s), cpu block and 2 gpu blocks. Seems like the bottom card is not getting proper flow so think I will swap to in series tonight then there is no doubt.

 

It was more aesthetics that I went with parallel anyway.

[Shaqo_Wyn]

General opinion is that performance is relatively similar between the two configurations but parallel tends to be less restrictive. Also have had read some comments that series is better for 2 gpu's and parallel for 3+. 

 

Currently I have my 780's in parallel using hard pipe to link them but am experiencing temp fluctuations, in particular after stress testing or gaming my temps dont drop back to the normal idle temps(around 20-25 degrees). Bottom GPU is worse than the top.

 

Think I need to swap to in series or reconfigure the inlet/outlet of my gpu blocks but before I do just wondering if anyone else has had issues running two GPU's in parallel before?

Hmm I haven't heard of issues like this. Generally series or parallel really doesn't matter. What parallel gains in flow rate it loses in performance, what series gains in performance it loses in flow rate. It could be ambient temps, other restrictions, a bunch of stuff. I'd love to hear if series solved your problem. Good luck!

[D3LTA9]

Hmm I haven't heard of issues like this. Generally series or parallel really doesn't matter. What parallel gains in flow rate it loses in performance, what series gains in performance it loses in flow rate. It could be ambient temps, other restrictions, a bunch of stuff. I'd love to hear if series solved your problem. Good luck!

Yeah at first I thought it was just an airlock as the temps stablised after cycling the pump a few times.

Now I have thought about it I'm pretty sure it's not because it is parallel but because I have the inlet port on the top gpu directly above the outlet port on the bottom gpu so if the water follows the path of least resistance a large amount can just flow straight through to my pump/res combo. Changing to a different inlet or outlet port probably would fix it but I think to be certain I will swap to in series. Will post pics of the build and let you guys know anyway.

[coalminer071]

General opinion is that performance is relatively similar between the two configurations but parallel tends to be less restrictive. Also have had read some comments that series is better for 2 gpu's and parallel for 3+. 

 

Currently I have my 780's in parallel using hard pipe to link them but am experiencing temp fluctuations, in particular after stress testing or gaming my temps dont drop back to the normal idle temps(around 20-25 degrees). Bottom GPU is worse than the top.

 

Think I need to swap to in series or reconfigure the inlet/outlet of my gpu blocks but before I do just wondering if anyone else has had issues running two GPU's in parallel before?

can we perhaps see what ur running? the loop itself

[D3LTA9]

can we perhaps see what ur running? the loop itself

 

yeah sure, but umm real noob spec question, what is the best way to upload a pic? I tried to link to another forum which I have a pic up in but wont allow me to. 

[coalminer071]

just paste the http onto here? doesnt it work?

[D3LTA9]

just paste the http onto here? doesnt it work?

 

Yeah wouldnt let me link to where I have the pic uploaded. Only other place is my google drive but no one will be able to see them other than me. Either way have swapped to a in series config and has sorted all my temp issues. Just did a couple of runs through heaven and max load temps of my 780's were mid 30's with a 2 degree delta between top and bottom cards. Will do some heavier testing soon.

 

So yea, lesson learnt was no matter how familiar you think you are getting with water cooling you can still make a stupid mistake. It was as I thought above,  the water was pretty much going straight past my cards due to the inlet and outlet ports being directly in line with each other, not using alternate ports that force the water through the blocks. I will get some decent pics sorted soon and post up a build log for every to see. Will also try a (proper) parallel config at some stage just to observe temp differences. 

 

Thanks for anyone help given everyone. Now to see what kind of overclock I can get out of my 4790K. 

[coalminer071]

Yeah wouldnt let me link to where I have the pic uploaded. Only other place is my google drive but no one will be able to see them other than me. Either way have swapped to a in series config and has sorted all my temp issues. Just did a couple of runs through heaven and max load temps of my 780's were mid 30's with a 2 degree delta between top and bottom cards. Will do some heavier testing soon.

 

So yea, lesson learnt was no matter how familiar you think you are getting with water cooling you can still make a stupid mistake. It was as I thought above,  the water was pretty much going straight past my cards due to the inlet and outlet ports being directly in line with each other, not using alternate ports that force the water through the blocks. I will get some decent pics sorted soon and post up a build log for every to see. Will also try a (proper) parallel config at some stage just to observe temp differences. 

 

Thanks for anyone help given everyone. Now to see what kind of overclock I can get out of my 4790K. 

Good job on fixing ur problem. im still curious on my own.

what is your ambient temps for u to get mid 30s btw?

[B NEGATIVE]

Series is cheaper.

With a single pump in parallel it would become hard to get equal water flow.

Nope.

Flow will be even between the 2 cards.

 

Parallel is really for quadfire,multi CPU setups with a dual pump solution,the quartered flow thru each card is improved by the addition of an extra pump. This gives a more even temp range for the cards.

 

Personally,serial is what I recommend over parallel in everyday use,ie 2 gpu's and a CPU loop.

Remember this,2 GPU's=Halved flow thru each,3 GPU's=A third of the flow.....4 GPU's=1/4 flow thru each card,if you do not have adequate pump power ,,,well, you can see where this is leading

 

I use serial even on my SR2 which is a tri-sli,dual CPU rig,card temps are within 2c of each other....36/38c loaded

[Nineshadow]

Nope.

Flow will be even between the 2 cards.

 

Parallel is really for quadfire,multi CPU setups with a dual pump solution,the quartered flow thru each card is improved by the addition of an extra pump. This gives a more even temp range for the cards.

 

Personally,serial is what I recommend over parallel in everyday use,ie 2 gpu's and a CPU loop.

Remember this,2 GPU's=Halved flow thru each,3 GPU's=A third of the flow.....4 GPU's=1/4 flow thru each card,if you do not have adequate pump power ,,,well, you can see where this is leading

 

I use serial even on my SR2 which is a tri-sli,dual CPU rig,card temps are within 2c of each other....36/38c loaded

Exactly what I was saying.

Parallel means the water flow will be split.

You will need a better pump to get as much water flow with a parallel loop as in a series loop.

 

That equal water flow was referring to the water flow in the series config.

[D3LTA9]

Good job on fixing ur problem. im still curious on my own.

what is your ambient temps for u to get mid 30s btw?

Yeah sorry I cant offer any more advice for your flow rate issue but as I said as long as your temps remain in check I wouldnt be too concerned. Its mid winter over here so let just say its COLD! haha best time for benching though, probably somewhere around 18 degrees as I did have the fire on may even be less as I havent checked.

 

Also I am not sure how heavy heaven is on GPU's so I expect to see a bit of an increase when I do some proper in game testing tonight. Also that is just running each card at 1ghz core clock at around 1.2v. Will be looking at running them around 1400mhz like I had my single 780 at with a large bump in voltage to near 1.4v (not stock bios so unlocked voltage).