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Puck

CPU waterblocks on Crossfire 7970+MCP655 Mod

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***WARNING, VERBOSE WALL-O-TEXT. IMPATIENT POSTERS SKIP TO TL;DR :)***

For a little bit of background, I was running a Sapphire 7970 when Dwood started making his brackets, which interested me since I was mining LTC and my temps would break 80c on the stock reference cooler. I ordered a custom lip bracket one right before he stopped taking orders, and threw a lapped H70 on my card with stellar results like shown in this thread here. My temps dropped from 84c stock, to 79c with replaced TIM, to 58c with the H70. I then did a few simple mods I never posted - replaced the crappy rigid ribbed tubing to standard clear tubing, added a Phobya tube res, and replaced the stock fans with 80cfm server fans. Now I was running at 55c full load, and was very happy(for a while).

A good deal popped up on here, which ended with me adding a second 7970 to my rig. Of course I wanted to ditch the same stock cooler, but I had a couple things to think about. Dwood was no longer taking orders on brackets, I didn't want two separate AIO loops crossing ugly lines all over my case, and I didn't trust the terribly weak stock H70 pumps to push two cards and a bigger rad. This of course led me to the logical choice of adding a second custom loop to my rig, but being cheap and a pretty slick modder, I looked at my parts lying around first - specifically the 280mm Aquacomputer Airplex Modular radiator, Enzotech Sapphire CPU block, and extra MCP655 pump top from an old dead pump...

***Mod Starts Here!***
The Enzotech Sapphire RevA. is a big, solid copper waterblock popular during the 775 days. Performance wise it is mid pack compared to other blocks of the same timeframe, but it was one of the lowest restriction waterblocks around and was way cheap in price. This made it perfect for beginning watercooling loops - it was only around $45 bucks new at the time, extremely low restriction so didn't need huge pumps, and performed better then a few more expensive blocks. While the low restriction made it perfect for a GPU setup that has to run flow-killing 90* adapters, the size and weight is an issue. I did some rough measurements and think I can get one in-between the two 7970s if I use non-rotating low profile 90* fittings and stick to 1/4" tubing. I have a horizontal mobo so the weight is not nearly as big an issue as with a vertical mobo, and even with dual GTX GenII 480's and dual pumps I have plenty of room in the bottom section of my custom Extended Ascension. I ordered a second identical Enzotech block that I found for sale on this forum, and a third 655 from a different forum, then got to modding what I have.

First thing I did was mod my spare 655 top to accept G1/4" fittings to reduce it to 1/4", since I did not feel like spending $30 on an aftermarket top. I cut off the stock plastic 1/2" barbs with a dremel, then tapped them with a 1/4" NPT tap. Note that G1/4" and NPT are not exactly identical threads, but in plastic it is "close enough" to work. The first few threads screw in perfectly hand tight, then you torque the last couple with a wrench and it corrects the difference between the straight and tapered threads. Now they screw in perfectly by hand, and I used a beveled drill bit to cut a recess for the O-ring. I was surprised to see that even though the 655/D5 pumps have "permanent" 1/2" ID barbs, the inside routing leading to them is noticeably smaller. I would imagine porting the stock top may actually be worth a bit of flow in a 1/2" tubing setup, but don't have the time nor desire to test that since this loop is using tiny 1/4" ID tubing anything. Nothing too exciting here, this is the finished result - awww, aren't those little barbs cute???:
Ao84V6o.jpg?1


Next step was to mod the block and bracket. This was pretty straight forward...I mocked up the hole spacing using the stock cooler I had lying around from my old card, then drilled it through. I then used a dremel to trim down the edges on the block itself since it will just barely (~1mm)interfere with the bolts I will use to mount it. After that all I will do is bolt it to the card using the stock retaining bracket on the back and some machine screws+bolts. I only pulled the top vanity plate off the card since I want to paint it red, it doesn't need to come off. Here's another boring, crappy pic to show what I needed to trim:
nmd2MKV.jpg?1

Tomorrow I should have my 90* adapters in, so can mock it up and make sure everything fits while I wait my my pump to get here. Fingers crossed I won't have to dremel up the adapters to screw them in, the ports are pretty close together on the block.

***TL;DR***
I am about halfway through putting two Enzotech CPU waterblocks into a crossfire water cooling loop in a custom Mountain Mods Extended Ascension case. Modded my MCP655 to accept G1/4" barbs, and modded the block to bolt through on an AMD GPU. Waiting on pump to arrive to install modded top on it and finish/test loop.

Edited by Puck

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How will you cool the VRMs and RAM? In my experience the VRMs tend to be the limiting factor long before the core temps rise to oblivion.

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How will you cool the VRMs and RAM? In my experience the VRMs tend to be the limiting factor long before the core temps rise to oblivion.

Same way as I cool them now with the H70 - Zalman ram sinks for the GDDR5, and a hacked up stock cooler for the VRMs. With a fan bracket to get some airflow they end up running quite a bit cooler then stock.

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Got the barbs installed, had to use elbows then barbs because the normal 90* barb fittings are too close together to screw in.

Still a very tight fit! The bottom piece is the stock backplate bracket that I will use for some spring tension to prevent over-tightening.

6LfBXgA.jpg?1
 

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Still waiting on the second Enzotech block before I mod the stock cooler for a VRM plate and install them both together. It is a tight fit, but everything goes together fine. Strangely enough, I was going to run two braces off the original mounting holes for a 92mm fan but apparently the hole spacing on socket 775  is the same as an 80mm fan, so I can just bolt one on the side over the VRMs once they are sinked.

 

yYjCp04.jpg?1

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Nice, I had seen some CPU waterblocks fitted on GPUs before, but they went the ghetto route using plastic ties.

Seeing that you used screws makes it in the higher class mods.

 

Still, props for modding the pump with different threads, as I don't even have the courage to put water in my case,
let alone modifying the joints, the most susceptible spot for a leak.

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Haven't had time to post a real update, but after a few snags I do have it all together working amazing. After an "Extreme HD" Preset Valley run my core temps on both cards never passed 42c, and VRMS were 59/54 . Down from 55c with the modded H70, (57c with stock H70). 15c cooler then a stock AIO mod, and a whopping 42c cooler then stock - it literally cut my load temps in half vs the stock cooler :).

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