It's been a few years since I've water cooled anything. Since my systems rarely stay together for more than a few months, it just doesn't make sense to break out the triple and quad radiators, pumps, blocks, tubing and reservoirs. If you ask about AIO cooling, I'll tell you that Noctua does it just as good with half of the hassle. Sometimes it's nice to put forth the effort, get out the storage bins filled with cooling parts and set out on a mission though.
Then again, sometimes it's just not needed. Unfortunately, sometimes you start down a path and later realize you're going in the wrong direction. Today's editorial is about starting in the wrong direction, but later figuring out we were right where we wanted to be all along.
Since Computex, I've gathered a Z87X motherboard from each of the major manufacturers to write an editorial on new features I personally find interesting. GIGABYTE was kind enough to send over their latest flagship Z87X board for Intel's 4th generation Core processor, Haswell. The GA-Z87X-OC Force uses new digital VRMs from International Rectifier. The new digital design means the VRMs run cooler than traditional MOSFITs, but GIGABYTE took the design of the OC Force and G1.Sniper 5 to a new level, incorporating liquid cooling in the PWM cooler.
Let's take a look at the new OC Force and see the new International Rectifier digital PWMs that use a single chip to replace the traditional 4-piece MOSFIT/Driver design.
GIGABYTE Z87X-OC Force
The GA-Z87X-OC Force is GIGABYTE's latest badass overclocking flagship motherboard. As the flagship model, the OC Force packs nearly every bell and whistle offered for overclocking and goes far beyond what we expect to find on a traditional motherboard. Shawn will have a full review of the GA-Z87X-OC Force soon and will cover all of the features in detail.
We're focusing at the area around the CPU socket today, the massive heat sink specifically and the new International Rectifier IR3550 PWMs under it. As you can see, the GIGABYTE GA-Z87X-OC Force looks a lot different in this area than most of the other motherboards on the market. The heat sink is massive and it also doubles as a liquid cooling block for extreme overclocking.
Here we see the same area without the heat sink. There are nine PWMs on one side and an additional seven running across the top.
GIGABYTE calls this OC Cool and in the lower right side of the image above we see the liquid cooling tubing to the processor and the PWM cooler before going back to the pump.
International Rectifier IR3550 and Test System Setup
International Rectifier IR3550
Each IR3550 chip has 30 pins along the side.
The PowIRStage specifications page shows a peak efficiency rating of 95% at 1.2V and an IOUT max of 60 amps.
What the IR3550 allows GIGABYTE to do is replace the traditional 4-chip MOSFET design with a single IR3550 that's very efficient.
Test System Setup
I grabbed a few parts sitting around the office and pieced a system together. In the coming days we're moving the SSD test platform over to 4th generation Core processors and Z87X chipsets.
Originally, I started this project to test the new PWM cooler, but the article took a turn while testing.
I think you'll agree with our findings. I do want to note a few things before we get started, though. We used an Intel retail heat sink and cooler for the CPU simply because it allowed us to use the thermal imaging camera. All of my other heat sinks are Noctua designs and very large.
In some of the images you may see black tap covering components. Any highly reflective surface makes the thermal imager report a false reading. The tape is thin and used to cover up anything that shines like the CMOS battery or the silver area on the heat sink.
We've already stated that going into this article we wanted to test GIGABYTE's new thermal solution for the PWMs. Before we could get started, we needed to determine the base temperature.
To start with, we clocked our CPU at 4.0GHz and loaded the processor with various CPU benchmarks. What we found was, the motherboard around the PWM area didn't actually get that hot even after an hour of stress tests. In fact, the only area on this half of the motherboard to see a significant rise was from the PLX chip just under the CPU cooler on the image (M6).
At this point in the test, I'm under the impression that GIGABYTE's new PWM cooler is amazing. With temps like the set we ran we needed to find out what happens when we take the heat sink off.
In the image above, we removed the PWM heat sink and stressed the CPU with performance benchmarks running in a loop. Surprisingly, the warmest IR3550 only reached 45C and a majority of the digital PWM chips hovered right around 40C with am ambient room temperature of 20C.
In the image above you can see a thermal probe going to Measure Point 1.
The temperature probe connects to a data logging device that records three samples per second. In the graph above, we see the temperature ramp up during load of the top left PWM while under load.
In the video embedded above, we see the system with and without the heat sink installed. In both cases, we used a timeline for testing with Cinebench 11.5 with the computer shut down and at room temperature to start with.
Cinebench starts for the first time at 1 minute and 20 seconds. A new Cinebench CPU run starts every 1 minute and 10 seconds after so at 2 min 30 sec, 3 min 40 sec, 4 min 50 sec and finally at the 6 minute mark.
Most of the PWMs reach 40C, but nothing goes over 45C.
For most of us the GIGABYTE Z87X-OC Force is more than we really need. That said, we are overclockers and most of the time the only word we truly understand is MORE. There is nothing wrong with that, but it's always important to understand the consequences of our actions.
In this case we need to understand that the new digital PWM that GIGABYTE used on the OC Force produces very little heat under a fairly typical overclock for a lot of people. Haswell processors are capable of achieving 5GHz on high-end air cooling and off the shelf liquid cooling. Once you get to 5GHz though, the CPU produces quite a bit of heat. If you are using the same loop for your CPU and voltage regulation via OC Cool, you quite possibly are increasing the PWM chips temperature, since the CPU heat will then run past the PWM chips.
At 5GHz with a Noctua D14 running three fans, the PWM temperature increased another 6C for most chips and two finally broke 51C. The CPU on the other hand was well into the 85C range, but only needed a slight voltage bump to reach the 5.0GHz (4.9GHz actual) mark. If we ran liquid cooling to the CPU, our overclock wouldn't have increased by much. If we ran liquid cooling to both the CPU and the PWM block that GIGABYTE supplies with the OC Force, we would have seen an increase in PWM temperature.
Maybe GIGABYTE was trying to give us another radiator by placing a fan on the PWM cooler? That made for a nice joke on Facebook, but in order to actually use the PWM cooler, we suggest only using it on a separate loop and don't think you need it unless cooling the CPU with liquid nitrogen or an exotic setup with liquid helium or the like.
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