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post #61 of 77
Quote:
Originally Posted by tsm106 View Post

It does add a degree of restriction over regular links because the path gets more complex but at this point I don't think it matters. Just throw more pump at it. Why'd you guys decide on dual parallel over just quad parallel btw?

Flow rate within each GPU. The restriction of 4 in 2x2 parallel/series is the same as a single block and half the flow rate. Four in full parallel is 1/4 the restriction of a single block, but divides flow rate by four. If you consider an optimal flow rate of 2gpm, in 2x2, each GPU gets 1gpm; in full parallel, each would only get 0.5gpm.
Edited by Electrocutor - 8/31/12 at 7:53am
post #62 of 77
Quote:
Originally Posted by Electrocutor View Post

Flow rate within each GPU. The restriction of 4 in 2x2 parallel/series is the same as a single block and half the flow rate. Four in full parallel is 1/4 the restriction of a single block, but divides flow rate by four. If you consider an optimal flow rate of 2gpm, in 2x2, each GPU gets 1gpm; in full parallel, each would only get 0.5gpm.


His overall loop flow would go up changing that equation wouldn't it?
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post #63 of 77
Quote:
Originally Posted by tsm106 View Post

His overall loop flow would go up changing that equation wouldn't it?
No, or only by a tiny bit. His restriction in a CPU + 2x2 Quad GPU setup is the same as CPU + GPU. He's planning to use a MCP35X2 pump, so you wouldn't want to decrease the resistance of the loop any further or there would be no benefit. Also, the flow through the rads does not keep temps down on your GPUs, higher flow through the GPUs does.

People get so confused about series vs parallel so I may do a write-up later to help explain it all. The key is that you want to be in series unless going to parallel or partial parallel will increase your flow in the water blocks enough to warrant parallel. In the case of 4 GPUs, having 4 GPUs in series would create substantial restriction, so you try moving them into 2x parallel. The flow through the CPU block will be MUCH higher this way and the flow rate through each GPU block will be the same or slightly faster this way. Looking at 4x parallel, there would be very little if any CPU block flow difference and you've cut the flow to each GPU in half.

It is very much pump dependent, and you use your pump's PQ curve data to decide which setup is best. A pump does not have infinite pressure at 0gpm flow and does not have infinite flow at 0 pressure, so you want to figure out the best flow rate/pressure combination.

In this particular case, he has 6 radiators, a CPU block, and 4 GPUs. We'll look at 2gpm overall flow: 6xseries rad=2.4psi, raystorm cpu: 2psi, 2x2 series/parallel heatkiller gpus: 3psi; total=7.4psi; at 2gpm, the MCP35X has about 10.2psi, so you have room for the restrictions of tubing, elbows, etc and will still probably end up with a bit higher than 2gpm: likely about 2.3gpm, meaning the GPUs each have about 1.15 gpm through them.

Take a look at the MCP35X2 PQ curve: MCP35X2 (Click to show)

At 3.5gpm, the Raystorm block is at around 4.9psi (the Raystorm Copper would be 6.5psi). That's higher than the pump can supply, and doesn't consider anything else in the system, so there is no way to get to the needed 4.6gpm to match the flow of the 2x2 GPU setup.


As a note, if you put all four heatkillers in series, you'd be able to run the loop somewhere around 1.3gpm, but obviously you'd have 1.3gpm vs 2.3 gpm to consider for your radiator and cpu block heat transfer.
post #64 of 77
Or how about triple MCP's in series?
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post #65 of 77
Quote:
Originally Posted by thehighlander123 View Post

Or how about triple MCP's in series?

What would be the point? The more pumps you put in series, the higher your pressure and lower the cut-off flow rate.
post #66 of 77
you can use martins pump/flow/rad estimator and get a good idea of what would happen. I assumed gpu blocks are more restrictive variety and added in number compressions for all rads/blocks.

with all op components and all in series:
1 x mcp 35x get about 0.63 gpm,
2 x mcp35x, get about 1.0 gpm
3 x mcp 35x, get about 1.25 gpm

with same components,but putting 4 gpus in 2x2 parallel
1xmcp35x, all but gpus get 1 gpm, gpus get 0.5gpm
2xmcp35x, all but gpus get 1.4 gpm, gpus get 0.7gpm
3xmcp35x, all gut gpus get 1.65 gpm, gpus get .82 gpm
(since cpu temps more flow sensitive than gpu, this is best compromise)

same components but putting 4 gpus all in parallel
1xmcp35x, all but gpus get 1.3 gpm, gpus get 0.33 gpm
2xmcp35x, all but gpus get 1.7 gpm, gpus get 0.43 gpm
(basically this scenario sacrifices gpu flow/temps too much for cpu temps)
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post #67 of 77
Thread Starter 
Quote:
Originally Posted by opt33 View Post

you can use martins pump/flow/rad estimator and get a good idea of what would happen. I assumed gpu blocks are more restrictive variety and added in number compressions for all rads/blocks.
with all op components and all in series:
1 x mcp 35x get about 0.63 gpm,
2 x mcp35x, get about 1.0 gpm
3 x mcp 35x, get about 1.25 gpm
with same components,but putting 4 gpus in 2x2 parallel
1xmcp35x, all but gpus get 1 gpm, gpus get 0.5gpm
2xmcp35x, all but gpus get 1.4 gpm, gpus get 0.7gpm
3xmcp35x, all gut gpus get 1.65 gpm, gpus get .82 gpm
(since cpu temps more flow sensitive than gpu, this is best compromise)
same components but putting 4 gpus all in parallel
1xmcp35x, all but gpus get 1.3 gpm, gpus get 0.33 gpm
2xmcp35x, all but gpus get 1.7 gpm, gpus get 0.43 gpm
(basically this scenario sacrifices gpu flow/temps too much for cpu temps)

ohh i see...if i had done 2x separate loops,1st one with the cpu,mobo and a d5 pump(as there will be low restriction) and the 2nd with all 4 gpu's maybe in serial with an mcp35x pump(as there will be more restriction,will i have more head pressure and flow?well,i am doing a parallel loop by splitting the discharge of the mcp35x2 into 2 and making 2x sub loops
..so which way is better?
post #68 of 77
you will always get more flow with mcp35x than a d5, since even a cpu waterblock is enough restriction to make pressure more important for improving flow. d5's are a little quieter, mcp35x will always net .2 to .3 gpm better flow in any water loop.

making subloops is only going to result in uneven and very poor flow for the more restrictive components. only use parallel when things in parallel are exactly same. ie never run cpu block parallel with gpu blocks for example. or the result will be poor.

you are making something very easy, into something complicated with poor results.
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post #69 of 77
I bet you are from UAE, aren't you Abdullah? You're spending money on stuff that won't get you any better performance.
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post #70 of 77
There is no reason to have that amount of rads period. Having more rads does not mean better temps.All you need is a 240rx rad for the cpu and mb block) and a 360 rad or 480 rad for the gpus thats it.No reasion to have a card just for physx. You also dont even mention what cpu and gpus you are going to be using.
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