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Cooling an i7 3930k with a closed-loop...

Posted: Sat Dec 15, 2012 1:50 pm
by BIF
Hello:

Here are my build items and plans:

Intel Core i7 3930k
ASUS P9X79 WS LGA 2011 SSI CEB Motherboard
HIS X Radeon HD 7970 GHz Edition 3GB Video Card (Already Ordered)

The primary uses for this system will be audio DAW and occasional animation workstation. I'd like to fold with it at least during the cooler months. I have a day job, so this system will probably do a lot more folding than it will anything else.

At this time I do not plan to overclock this system, but that could change down the road. Folding will be CPU + GPU, and I would like to run it at 100% when folding.

Cooling Plans:

My original plans were to build a dual liquid cooling loop for the CPU and GPU, but since then I realized that my enthusiasm extended beyond my budget! So now I have also "cooled my jets" and I have decided to stick with the stock air cooler on the HD 7970 and put a new closed-loop liquid cooler in for the CPU.

My current Q6600 uses a Corsair H60 (I think?). It has a single 120mm radiator, and it has served this system very well for the last 3-4 years, even when folding recently at 75-80% CPU utilization. My case is a CM HAF 932, and the radiator is mounted on the inside rear panel.

The Big Question:

Does the i7 six-core processor require a larger radiator such as that with the H100, H100i, or even the Thermaltake CLW0217 Water 2.0 Extreme, or would a single-width 120mm radiator suffice?

I do not plan to recycle my current H60; in any event, it's probably time to replace it. But I am concerned a little bit about the requirements for a bigger radiator and the requisite increased number of fans and associated increase in noise. Please read on...

Additional Background:

When sitting in my "critical listening" position between the audio monitors, the HAF 932 sits on the floor, under my desk and just to the ouside of my right leg, which allows fairly uniform cable runs to everything on both sides of my studio, such as USB 2.0 and now 3.0 cables, Firewire cables, video monitor cables, eSATA cables, keyboard and mouse cables, etcetera. The "ceiling" of the case is partially obstructed by the underside of my desk, but it still has an indirect path, mostly to my right ear. Currently, there is a slow 230mm fan in that ceiling position and I cannot hear it at all.

I'm not quite ready to rack-mount this system, due to the massively long cable runs I'd have to employ (the rack would have to go way off to one side or the other, so half of the cables would have to be twice as long).

Sorry for the long-winded explanation, but given the position of the HAF932 (floor right side), I'd rather use a single-120mm sized radiator in the original "back panel" location, if it won't have any adverse effect on my six-core i7. A dual-sized radiator would require ceiling mounting in that computer case, and I'm afraid that 2 or 4 smaller 120mm fans on the ceiling of the case may project more fan noise than the original large slow fan that's currently in that position.

I hate fan noise. But I don't want to burn up my hardware, either. Opinions, experience?

Thanks in advance!

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sat Dec 15, 2012 2:30 pm
by Ryu Connor
The H60 or H80 will work fine. Personally I use the H100 as it doesn't block access to the DIMMs in a case that supports mounting the radiator up top (most Corsair cases). The H80 is a PITA with X79 IMO.

At the low settings the fans are quite quiet IMO.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sat Dec 15, 2012 3:19 pm
by BIF
Hi Ryu!

Yeah, I'm thinking the H100i or the similarly-sized double-length Thermaltake would work well, mounted up top like yours; even with my initial reservations.

My new logic: The bigger radiator will have added cooling capacity and so the 120mm fans probably won't need to ramp up as quickly, except maybe during animation, which I don't do all that often, or during folding, at which time I might not even be home to hear the noise.

DAW usage is not typically CPU intensive unless I'm using a lot of processor-heavy effects or instruments; also not a frequent case.

So for right now I'm leaning slightly in favor of getting the bigger unit and replacing the big slow fan on the ceiling.

All that's left to decide is .. Corsair or Thermaltake? They both have fan control software and I have watched both product videos on Newegg. I sort of like the Thermaltake becuase it has connectors on the pump. But that's probably a nit because once it's all plugged in, I would never ever want to unplug them anyhow.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sat Dec 15, 2012 3:46 pm
by cynan
Why would you go dual cooling loops? I'm pretty sure single loops have generally been shown to be more efficient. By more efficient, I mean that a single loop using the same number of radiators as dual loops combined will be more efficient at removing excess heat, overall. Plus they are easier to build. Just keep the loop as short as possible for best performance. The only time you need to worry about more than 1 loop is when you're cooling multiple components and you're worried that the pump will have difficulty circulating through all components on a single loop at a high enough minimal flow rate (about 1 gallon/min). If you are trying to overclock your CPU to the bleeding edge and need the best lowest possible temps for the CPU, then a dedicated CPU loop might be warranted, especially in a multi GPU system. But for 99% of computer use a single loops is the way to go. Plus, if you have multiple pumps, you can place them in series in a single loop in case one fails for peace of mind - which will serve you better in most cases than in a dual loop. But don't take my word for it, see the first post here.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sat Dec 15, 2012 5:13 pm
by mortifiedPenguin
BIF wrote:
My original plans were to build a dual liquid cooling loop for the CPU and GPU, but since then I realized that my enthusiasm extended beyond my budget! So now I have also "cooled my jets" and I have decided to stick with the stock air cooler on the HD 7970 and put a new closed-loop liquid cooler in for the CPU.
What exactly was your budget? There are a few (relatively) affordable kits out there that can get you started on custom water cooling. As I've said in previous threads, water cooling is just as much about the hobby as it is about getting good temps.

cynan wrote:
But don't take my word for it, see the first post here.

Summary:
extreme workloads: neither is better if load ratios are evenly balanced
normal workloads: single loop is better and potentially has pump redundancy.

Good link, cynan. Though is it just me or are there graphs missing?

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 12:34 am
by BIF
cynan wrote:
Why would you go dual cooling loops? I'm pretty sure single loops have generally been shown to be more efficient. By more efficient, I mean that a single loop using the same number of radiators as dual loops combined will be more efficient at removing excess heat, overall. Plus they are easier to build....


I was unaware of all this and this is the first time I've ever seen that Swiftech testing thread. Thank you for the reference.

mortifiedPenguin wrote:
What exactly was your budget? There are a few (relatively) affordable kits out there that can get you started on custom water cooling. As I've said in previous threads, water cooling is just as much about the hobby as it is about getting good temps.


Well, maybe up to a couple hundred. Among other things, I'm buying several monitors for this new build, and that's why the low $100 figures for the 240mm closed-loop systems is so appealing right now.

The CPU has always been my highest priority for water cooling because for better or for worse, all my prior systems' fan noise seemed to come from the CPU air cooler. I'm hoping that the HIS X 7970 card should be fairly quiet and that it won't need water cooling unless the GPU folding ends up pushing it hard enough to make it noisy.

Summary:
extreme workloads: neither is better if load ratios are evenly balanced
normal workloads: single loop is better and potentially has pump redundancy.


I don't know what that means... "if load ratios are evenly balanced"... Huh? If you're installing a single loop for all your major heat-sources, you don't have much choice because you have what you have, right? I'm buying the parts that I'm buying based on my needs and desires for specific capabilities. THEN I will cool what I have, right?

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 9:02 am
by MadManOriginal
I know water-cooling is sexy and all but I'm going to against the grain of the thread here...why not a good-performing tower style air cooler? I remember tests of closed loop coolers showing that they didn't perform remarkably better, either in temps or sound, compared to air coolers. But since noise is a big concern for you, there's another possible advantage to air coolers: the fan will be 'buried' further into the case than a water cooler radiator fan which is right next to the opening in the case. This might reduce CPU cooler fan noise even if you do have a case fan mounted where the radiator would have been.

It's hard to say for sure how this would work out, just some things to think about.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 12:07 pm
by vargis14
I recommend either the h80i or the h100i they both come with good monitoring software and the h80i is double thick and cools just about as good as the new h100i......it even is better then the old original h100.

I have the haf 922 and the h100s fit perfect in our cases. If I was you I would get the h100i and put the 200mm top fan in the side panel to cool the 7970 and chipset/vrms on the motherboard and graphics card. I would probably also get a couple high quality highest cfm 120mm fans that are under 30db sound wise for either a push pull setup. Or replacing the fans that come with the radiator.

If you setup a h100 push pull setup I would use the high quality fans as pull fans and the corsair fans as the push fans controlled by the software. :D

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 1:57 pm
by BIF
MadManOriginal wrote:
I know water-cooling is sexy and all but I'm going to against the grain of the thread here...why not a good-performing tower style air cooler? I remember tests of closed loop coolers showing that they didn't perform remarkably better, either in temps or sound, compared to air coolers. But since noise is a big concern for you, there's another possible advantage to air coolers: the fan will be 'buried' further into the case than a water cooler radiator fan which is right next to the opening in the case. This might reduce CPU cooler fan noise even if you do have a case fan mounted where the radiator would have been.

It's hard to say for sure how this would work out, just some things to think about.


Thank you for the input, and yes, I could use a tower cooler, but as noted in my OP, my case is a HAF 932. For those who may not know, the HAF series is mostly mesh-styled. Essentially, this is a very open case, which I like very much. But it does not shield the ears from the interior noise-makers.

Also, I just never liked the complications that tower coolers bring. Downforce on the motherboard, air directional issues, the potential obstruction of VRAM, MOSFET, memory slots, etcetera. And to me, towers are all noisy. Yeah, it's probably psychological at this point, but that is my reality. :P

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 2:10 pm
by BIF
vargis14 wrote:
I recommend either the h80i or the h100i they both come with good monitoring software and the h80i is double thick and cools just about as good as the new h100i......it even is better then the old original h100.

I have the haf 922 and the h100s fit perfect in our cases. If I was you I would get the h100i and put the 200mm top fan in the side panel to cool the 7970 and chipset/vrms on the motherboard and graphics card. I would probably also get a couple high quality highest cfm 120mm fans that are under 30db sound wise for either a push pull setup. Or replacing the fans that come with the radiator.

If you setup a h100 push pull setup I would use the high quality fans as pull fans and the corsair fans as the push fans controlled by the software. :D


This is sounding more and more like a good plan for me. I didn't know that the 80 was double-thick. That's actually ideal; because it would let me get the cooling capacity of the H100 but still continue to use the back-panel if I want to.

Whichever one I choose, I think I will begin with a "push only" configuration for simplicity and reduced clearance requirements. If I mount to the ceiling, then my existing big ceiling fan would just go into the parts bin, because the side wall already has an even bigger fan already installed, yay! :)

But before I buy anything, I should re-evaluate a DIY single loop for the CPU-only. I do like the idea of having pump redundancy.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 3:11 pm
by vargis14
I am pretty positive the h80i is push pull right out of the box. I have read the reviews and it has a fa tastic fan contoller usb controlled program. I kow you will not hqve any clearence issues plus with the double wide radiator you want that pill fan to help the air get through it at low fan speeds.
Cheers

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 3:19 pm
by just brew it!
FWIW I have been rather disappointed with the reliability of the fans Thermaltake tends to use on their cooling products. I have no direct experience with their watercooling kits, but the fans on many of their conventional coolers were problematic, at least up until 2-3 years ago (when I stopped buying them because of the crappy fans).

Themaltake and SilenX are the two brands of cooling products currently on my "avoid" list...

BIF wrote:
Also, I just never liked the complications that tower coolers bring. Downforce on the motherboard, air directional issues, the potential obstruction of VRAM, MOSFET, memory slots, etcetera. And to me, towers are all noisy. Yeah, it's probably psychological at this point, but that is my reality. :P

I've been quite happy with my CoolerMaster tower coolers. They're lightweight enough that the downforce does not seem to be excessive, they are narrow at the base so obstructions are minimized, and they allow mounting for either horizontal (front to back) or vertical (bottom to top) airflow. Yes they can be a little loud at full RPMs, but I tweak the fan speed profile such that they only ramp up to full RPMs if the system is running at 100% CPU load in a very warm room. Provided they are running at 75% or less of max RPMs they seem to be reasonably quiet.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 3:39 pm
by MadManOriginal
BIF wrote:
MadManOriginal wrote:
I know water-cooling is sexy and all but I'm going to against the grain of the thread here...why not a good-performing tower style air cooler? I remember tests of closed loop coolers showing that they didn't perform remarkably better, either in temps or sound, compared to air coolers. But since noise is a big concern for you, there's another possible advantage to air coolers: the fan will be 'buried' further into the case than a water cooler radiator fan which is right next to the opening in the case. This might reduce CPU cooler fan noise even if you do have a case fan mounted where the radiator would have been.

It's hard to say for sure how this would work out, just some things to think about.


Thank you for the input, and yes, I could use a tower cooler, but as noted in my OP, my case is a HAF 932. For those who may not know, the HAF series is mostly mesh-styled. Essentially, this is a very open case, which I like very much. But it does not shield the ears from the interior noise-makers.

Also, I just never liked the complications that tower coolers bring. Downforce on the motherboard, air directional issues, the potential obstruction of VRAM, MOSFET, memory slots, etcetera. And to me, towers are all noisy. Yeah, it's probably psychological at this point, but that is my reality. :P


Fair enough...I didn't know the case was largely mesh so there's little difference in having a 'buried' fan. As for the other things, I don't agree because there are workarounds and options but not going to debate it here :) Good luck.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 4:34 pm
by BIF
Vargis, JBI, and MMO, you all make very good points and I thank you for taking the time.

I will take all this under consideration and will follow up here either with additional questions or my decision, just to close the loop on our conversation.

Thank you all!

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 5:01 pm
by vargis14
I just wanted to add i am SO SO JEALOUS of that beast of a 7970 card you already bought. I have read the reviews on it and it overclocks like a monster on steroids! On top of that His makes fantastic cards and coolers that do not make as much noise as the competition. Please fill me in on how it overclocks and so on.

Also with our Coolermaster HAF cases with the honeycomb mesh design i have mine sitting on the left side of my desk so the solid side of the case is facing me. It really helps on cutting down on the minimal noise our big 200mm+mm fans mounted in the side panel with like 18db of noise...but you have to take into account the 120mm fans on the radiator that can be fully controlled to spool up only when necessary. The only negative thing about placing the case on the left side of you is you cannot see your hardware while your sitting down:) As for my front red led 200mm fan i am so glad they gave us a switch to turn the led's off on the fan.I blow out/clean my case , fans, and video cards every 3 months since they do not have filters on the side panel intake. But i have 2 big dogs and smoke.
Also the left side of my desk is up against a window and i have one of those dual window fans you can make one intake and one exhaust. So in the winter and cooler months its nice to have nice cold air blowing right into my case giving me right now a ambient temp of 10c. My gpu and cpu idle temps are 18c and 17c. In the summer a air conditioner goes in that same window:)

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 7:07 pm
by cynan
Just to add my 2 cents to the peanut gallery, I wholeheartedly agree that custom water cooling setups are not worth the fuss and cost unless you:

1) Want to push your overclocks beyond what you can do on air.

I have an X79 with a 3930k and a HD 7970. Both can be pushed to higher overclocks on a properly specced custom water cooling setup. I really noticed a big difference with the HD 7970 on water vs air. With my lowly Gigabyte card, I couldn't push much above 1200 Mhz for stable performance on air (and the Gigabyte Winforce stock cooler is no slouch). When I got it on water, idle temp clocks dropped from low 40s (deg C) to high 20s (yes, only about 5 deg above room temperature). Load temps went from high 70s to high 30s. The upshot was I could supply a bit more voltage (without hitting high temps/getting artifacting) and run stably at 1300 Mhz core clock (haven't tried to push beyond this). With a card that has a beefed up power circuitry, like I think that HIS card you ordered, results could be even better (chip lottery allowing).

If all but guaranteeing 1300 Mhz + (again, chip lottery allowing) overclock on the HD 7970 is not important to you, then you might as well stick with the stock air cooler. You should be able to hit 1200 Mhz easily enough with that HIS card...

2) You are looking to get into water cooling as a hobby in and of itself.

A water cooling setup can get you a bit less noise when pushing your hardware (as fans don't typically ramp up at load), but the cost of this benefit alone is pretty high. Plus, to get a really quiet water system, you generally need to go a bit overboard on radiator size/number so you can use more low-speed/larger/silent fans vs fewer high speed louder ones.

Then there is reliability. If I was leaving my computer on all day folding, I'd be a little worried about a pump failure (even though I've been running my cooling loop for the last 9 months without any such issues). Sure, you could add a second pump in series, but this adds to the already high cost.

BTW, there is a closed loop cooler for HD 7970, but at $190, I personally don't think it's worth it over the stock air cooler on the HIS, as a proper custom loop will get you better performance and not cost a whole lot more.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 10:13 pm
by vargis14
Yeah Cynan that artic cooling graphics card cooler works great but it only cools the gpu itself great, the Vrms only get cooled by air and its very important to keep them cool along with the graphics core itself. A custom water cooling block that cools the vrms and other circuitry with with water is the only way to go if you are going to cool your GPU with water.

I just wonder with the HIS cards custom circuit board if you can get a full coverage block for it. That would unleash all the power that card could dish out without going to liquid nitrogen or some other super cooler.

I know the HAF932 case can hold a nice 240mm radiator along with 2 120mm radiators along with a nice nice 5 1/2 inch x 2 front bay reservoir along with a beefy high flow pump :) Say goodbye to any cooling worries. That bad boy might hit 10 degrees over ambient max....even overclocked.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Sun Dec 16, 2012 11:50 pm
by BIF
vargis14 wrote:
...I just wonder with the HIS cards custom circuit board if you can get a full coverage block for it....


Well, once I decided on this HIS card, I vaguely remembered that it was not a reference card. I knew this would be a drawback with regards to my liquid cooling options. But I decided I wanted at least 5 monitors, 6 being ideal to give me room for a reserve port. All in a dual-slot card, which was also an ideal choice, even though it's quite expensive.

I know the HAF932 case can hold a nice 240mm radiator along with 2 120mm radiators along with a nice nice 5 1/2 inch x 2 front bay reservoir along with a beefy high flow pump :) Say goodbye to any cooling worries. That bad boy might hit 10 degrees over ambient max....even overclocked.


Yes, I too like the HAF932 design; and envisioned many possibilities from the moment I saw it, way back whenever that was. So far, so good, it's been an excellent case choice for me.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Mon Dec 17, 2012 9:03 am
by DPete27
Wanted to throw this up as a quick FYI. Newegg has the H100 for $80 after MIR with promo code EMCJHJB244 right now. That's obviously not the new model (H100i) but the price is decent.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Mon Dec 17, 2012 9:36 am
by vargis14
The new H80i and H100i both have a improved cold plate and increased diameter hoses. On top of that the original h100 is much louder then the newer models. Though a nice find But i hate rebates.

BIF is building his DOUBLE STUFF!!!! I know he is not going to worry about a few $ when the new H80i cools just as good and is quieter then the original h100. Plus i have yet to see a new H100i article where they use 4 fans instead of the 2 fans that come with it. It seems Biff is leaning torwards the h80i but i would love to see the performance of the new H100i with a push pull configuration.

As for a full coverage water block for the HIS 7970 I am sure one can be made or customized for the unique layout of the HIS circuit board...........but it will come with a steep steep price. But if I had the $ and it was my toy/project i just might do it:) IF i had the money to do that i would probably get a 3960x or even the new 3970x just to have the extra l3 cache and that little extra OC potential.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Mon Dec 17, 2012 10:32 am
by PainIs4ThaWeak1
My two cents...

I'm personally using a 3930K @ 4.2GHz (@ 1.385v?? IIRC) with an H100i using only the two included fans on the radiator (in a Corsair 650D, 2x GTX680's, a couple SSDs, with an old MKII 910W PCP&C PSU), and after altering the fan profiles within "Corsair Link" for the H100i to the pre-configured "Turbo" profile, the CPU always idles between 40-42*C, under load (a la F@H or LinPack) I've never seen temperatures above 72*C (under LinPack), and never any higher than 62*C under F@H. With any of today's games, I've never seen CPU temps come close to those numbers.

For me, that fits the bill, given the H100i performance vs. dollars spent.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Mon Dec 17, 2012 1:50 pm
by mortifiedPenguin
BIF wrote:
I don't know what that means... "if load ratios are evenly balanced"... Huh?
Pardon the late response... I was out for the weekend.

The article/post would make a bit more sense if we could actually see some graphs. My interpretation in the absence of said graphs is that if the load on both components generate roughly the same amount of heat, neither loop type "wins". However, typical workloads are usually asymmetric ones where one component is generating more heat than the other, you'll gain superior results with the other component due to the "added" capacity of the loop.

I have actually seen the "typical" results myself in my single loop. When at max GPU load, CPU temps increase only slightly and vice versa. Only in the situation where both are running at maximum (and the GPUs in this case produce more heat) do I see worse numbers but I think it's rare that you'd encounter a real-life scenario like that.

BIF wrote:
If you're installing a single loop for all your major heat-sources, you don't have much choice because you have what you have, right? I'm buying the parts that I'm buying based on my needs and desires for specific capabilities. THEN I will cool what I have, right?
To be honest, I'm not really sure what you mean here. But, since I'm a bit late in returning to the party, feel free not to address this point.

--

At the end of the day, as a few other Gerbils have alluded to, if you're really just looking keep things acceptably cool and quiet and not necessarily start a new hobby, high-end air and/or closed loop systems are probably a lot better use of your money than doing a full custom loop. It really starts to add up and sort of turns into a bit of an obsession :wink:

Re: Cooling an i7 3930k with a closed-loop...

Posted: Mon Dec 17, 2012 6:37 pm
by cynan
mortifiedPenguin wrote:

The article/post would make a bit more sense if we could actually see some graphs. My interpretation in the absence of said graphs is that if the load on both components generate roughly the same amount of heat, neither loop type "wins". However, typical workloads are usually asymmetric ones where one component is generating more heat than the other, you'll gain superior results with the other component due to the "added" capacity of the loop.

I have actually seen the "typical" results myself in my single loop. When at max GPU load, CPU temps increase only slightly and vice versa. Only in the situation where both are running at maximum (and the GPUs in this case produce more heat) do I see worse numbers but I think it's rare that you'd encounter a real-life scenario like that.


Yes. That's the gist.

Due to the high specific heat capacity of water, even the added heat from 1 or 2 high TDP GPUs at load will not significantly impact the ability of the water to pull heat away from the CPU block. This of course assumes that you have adequate radiators/fans in your loop (which for a high TDP GPU and processor like the 7970/SB-E probably starts at about 2x 120mm radiators each - or 4 in total for 1x HD 7970 and 3930k). I currently run 1 3x120mm and 1 2x120mm rad (5x120mm total) for my single HD 7970 and 3930k and this seems to be more than adequate - I could probably squeeze in another HD 7970 without too much worry. This obviously varies a bit depending on how high performance the rads are and fan speed. This type of allocation will generally net you a 10-15 deg delta between load and idle temps.

With a single loop, for example, say your nominal water temp in your loop when the PC has been idling for a while is 27 deg C (generally would be a couple/few degrees above room temp). Say the 27 deg water keeps a moderately overclocked (lets say 4.4 Ghz) 3930k at 35 deg C when idling and 50-55 deg C when the 3930k is at load under these conditions. You start a gaming/folding session with a pair of overclocked HD 7970. After a couple of hours, the GPUs running at full load (in conjunction with the CPU running at load intermittently to supply the GPUs, run the game, etc) water temp goes up from 27 deg C to 35 deg C. All that will happen is the 3930k will now be a few degrees higher when idling and at load (say from 30 to mid 30s at idle and from low 50s to high 50s at load). The upshot is that the CPU is still being kept cooler than it would on air or by most/all closed loop cooling systems. Stability and performance of the PC will not be affected.

Later on you perform a CPU intensive only task. Now the CPU has added cooling capacity from the GPUs...

In a dual loop scenario similar to the above, with the GPU(s) on a separate loop, with the same number of total radiators/fans, the GPUs will not be able to dissipate as much heat as efficiently. The CPU will be able to dissipate more heat, but in the above first scenario, you probably WANT the extra "shared" heat dissipation for the GPUs because the CPU simply doesn't need it. So here a single loop likely wins. And this type of scenario is encountered more often, I would think, in everyday computing.

Now, if you are doing max overclocking testing on the 3930k (or the GPU), the coldest water temperature might get you stable at that few extra Mhz/bit more voltage. This kind of thing is where segregated loops might be warranted.

But this generally requires overspeccing each loop with more radiators than a single loop would have in total. Added to the extra cost for reservoirs and pumps, the added complexity of the build, the need to bleed and drain 2 loops instead of one when doing maintenance and it's just not worth it for most usages.

If you always run with the CPU and GPU maxed out simultaneously, then dual vs single loops makes less of a difference. But this is only if the cooling capacity is balanced per the cooling requirements of each loop (ie, if you have 5x120mm radiators in total, you then have to worry about which loop gets which radiator(s). With a single loop, you don't need to worry about this sort of balancing as everything is lumped together. Simpler.

Also, I think it's been shown that it does not matter where in the loop you put the rads (ie, making sure you have a radiator in between each component being cooled). Generally, the shorter you can make the loop the better the discernible performance. This also keeps things more tidy.

Re: Cooling an i7 3930k with a closed-loop...

Posted: Thu Dec 20, 2012 6:46 pm
by BIF
Penguin and Cynan:

Thank you both, between the two of you I believe I've grokked it!

Another excellent educational opportunity and another satisfied student of Tech Report University! Go TRU!