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Thanks to XFX, we have the MERC308 BLACK RX 6600 XT on the test bench today. This is the third iteration of AMD’s RDNA2which is a pared-down die to give us NAVI 23. And according to AMD, it sits in the product stack right behind the RX 6700, is ideal for 1080p gaming, and is a bit more budget-friendly. If you can find one that is.
The MERC308 BLACK version of this card brings a robust VRM design, a large aluminum triple-fan shroud with a plated copper heatsink, as well as an overclock out of the box. The 2.5-slot cooling solution includes an LED light bar on the card’s facing edge showing the “XFX” logo, RADEON branding, and card model (RX 6600 XT). A full-length aluminum backplate with the MERC logo cleans up the card’s backside while adding some rigidity. Overall, it’s a good-looking card and fits in well most build themes.
Performance-wise, this overclocked card performed well in our testing trading blows with the RTX 2070 and 2080 while even outperforming the latter in some tests. The MERC308 RX 6600 XT did this while using very little power staying at 145 W (GPU only) while running stock. This card really shines at FHD (1920 x 1080) and is capable of WQHD reaching well over 60 FPS in most gaming benchmarks. 4K UHD is a bit of a stretch for any of the cards mentioned with all the details turned up but certainly possible with a slight quality reduction.
The MSRP for the XFX MERC308 BLACK RX 6600 XT is set at $410.00, a $30 premium over the 6600 XT reference model’s MSRP. This premium has benefits bringing with it a factory overclock, improved power delivery, solid aluminum construction, a premium copper-based cooling solution, and a three-year warranty. Let’s get this card to the test bench and see how well it does.
Specifications and Features
|AMD Radeon RX Series Specifications
RX 6900 XT
|AMD Radeon RX 6800 XT
|AMD Radeon RX 6800
|AMD Radeon RX 6700 XT
|XFX MERC308 RX 6600 XT
|Navi 22 XT
|TSMC 7 nm
|16 GB GDDR6
|12 GB GDDR6
|8 GB GDDR6
|16 Gbps GDDR6
The XFX MERC308 BLACK RX 6600 XT uses the Navi 23 core measuring 237 mm2 with 11.1 billion transistors. The XT variant offers 2,048 stream processors, 64 ROPs, 128 TMUs, or approximately half of the RX 6800. This holds true for the infinity cache sitting at 32 MB and the 8 GB of GDDR6. For more information on AMD’s High-Speed design, Infinity Cache, and RDNA2 features, check out our launch day review for the RX 6800 and 6800 XT.
The big difference from the reference cards is the cooler, power delivery, and clock speeds. In this case, the MERC308 BLACK is spec’d at 2428 MHz Game Clock and 2607 MHz Boost Clock, a marginal increase over the reference design. The game clock is where the card runs most of the time and should fare well for the MERC308 in testing.
XFX’s Speedster lineup for the RX 6600 XT cards consists of the MERC308 BLACK, which sits at the top of the stack, followed by the QUIK308 BLACK; both come with a factory overclock. The MERC and QUIK are basically the same cards as far as looks with the triple fan design. The QUIK, however, does not have the LED lighting found on the MERC series. These are followed by the SWIFT210 CORE, which is a dual fan design with no factory overclock. XFX has changed its naming convention with the RX 6000 GPUs; MERC stands for Mercury, QUIK is quicksilver, and SWFT is swift. We also have BLACK, ULTRA, and CORE, with BLACK being the top of the line. The 319, 309,308, and 210 have meaning; 319 is three fans, including 100 and 92 mm, while the 309 is three fans, all of which are 92 mm. The 308, much like the 309, consists of three 80 mm fans, and the 210 is a dual 100 mm fan setup.
Our XFX RX 6600 XT is the MERC308 BLACK which uses the 308 heatsink – equipped with three 80 mm fans. The new 9-blade fans are designed for high efficiency and longer life thanks to the sleeve bearings and blade shape. This combination of three fans delivers high airflow and low noise even while overclocked.
XFX also redesigned the heatsink to improve airflow dynamics and cooling efficiency. The premium 2.5-slot aluminum heatsink has 354,995 square mm of surface area for maximum heat dissipation. We also have a full plated-copper heat spreader with four 6 mm heat pipes that snake through the heat sink. Additionally, that card uses a lot of high-quality thermal tape aiding in thermal transfer from the core, memory, and power bits. In our cooling tests, the MERC308 BLACK RX 6600 XT peaked at 74°C under load at stock speeds and was quiet in doing so.
XFX doesn’t have any additional software for overclocking, but Radeon Adrenalin works fine as well as third-party utilities such as MSI afterburner for tweaking the core and memory speeds. The MERC308 also doesn’t include any controllable RGB LEDs but has a subtle back-lit LED light bar showing the RADEON and XFX logos along with the RX 6600 XT model.
The cast aluminum backplate helps reduce PCB bend, GPU sag and provides physical protection from the PCB components on the back of the video card.
FULL DIGITAL PWM POWER DELIVERY
TThe XFX MERC and QICK 308 6600 XT Black utilizes a 6+2 phase design. The default BIOS delivers 145 watts of power. AMD’s reference specification for the 6600 XT is 130 watts.
COPPER GPU HEAT SPREADER AND HEAT PIPES.
Plated Copper Heatpipes with copper base offering tremendous cooling across both GPU and memory.
TRIPLE FAN DESIGN
9 Blade High-Efficiency Sleeve Fans
3x 80mm (76mm blade)
XFX / RADEON LIGHT BARD
The MERC 309 Black doesn’t feature extravagant RGB lighting; it has subtle AMD and XFX logos to show off the power within your rig. The floating design allows for additional air flow.
IT’S MORE THAN JUST DESIGN
Every iteration isn’t just designed for design’s sake; we take everything we learned from the last model and fine-tune, adjust, modify to make our GPU design as honest as we can. Nothing fancy or unnecessary; just want is needed to increase performance and improve quality.
Retail Packaging and Accessories
Retail packaging for the XFX MERC308 BLACK RX 6600 XT has a vertical theme. It includes the XFX branding and MERC308 Black model on the front with a couple of features (1080p FHD support, 8 GB VRAM, PCIe 4.0). Turning the package around offers a picture of the card along with a more extensive list of features.
Inside the box, the card sits snug in form-fitting foam to keep it secure during shipping. The card is wrapped in an anti-static bag, and there are no included accessories to speak of, just some warranty, installation, and driver information.
Meet the XFX Speedster MERC309 BLACK RX 6600 XT
The XFX MERC308 BLACK RX 6600 XT has a clean and neat appearance. The majority of the card is black, with some brushed aluminum accents around the edges. The three fans also have a brushed aluminum ring with the XFX logo on the hubs. As mentioned, the MERC308 has some backlighting on the outer edge, mostly white aside from the RX marking, which is done in red. XFX has also included an Aluminum backplate bearing the MERC and XFX logos, offering excellent heat dissipation, PCB protection, and rigidity. The MERC308 shouldn’t have any issues fitting in with most build themes.
A Closer Look at the XFX MERC308 Black RX 6600 XT
Zooming in on the I/O layout, we’re greeted by three DisplayPorts (v1.4 with DSC) and a single HDMI (v2.1) port—the latter supporting up to 4K@120Hz. The card’s maximum resolution is 8K (7680 x 4320). While the card does not exhaust air directly out of the I/O plate, there are holes in it to let a bit of the warmed air out. Power is sent to the GPU through one 8-pin PCIe connector. Combined with the PCIe slot, the card provides up to 225 W of in-spec power, more than enough for this 160 W (TBP) card even while overclocked. Next to the PCIe power connectors is a dual position BIOS switch. According to XFX, both positions have the same BIOS “at this time.” Whether or not that will change hasn’t been shared with us.
XFX uses a premium aluminum heatsink on this MERC308 BLACK RX 6600 XT. The 2.5-slot solution uses four 6 mm heat pipes soldered to a plated copper heat spreader which contacts the GPU die and memory ICs. We also have three 9-blade sleeve fans to push plenty of air through the heatsink and are all contained in a solid aluminum shroud that also adds rigidity and aids in heat dissipation. This premium cooling solution pushes the card’s dimensions to 10.8 x 4.5 x 2-inches (274 x 114 x 50 mm).
After fully removing the heatsink, we’re finally able to see the PCB. We see an unmarked Navi 23 silicon and its 237 mm² die area. Surrounding the GPU are four Samsung memory ICs (K4ZAF325BM-HC16) specified to run at 16 Gbps. The memory uses a 2-phase design with an OnSemiconductor NCP81022N controller feeding OnSemi NCP302045 45A MOSFETs. The GPU core is controlled via an 8-phase International Rectifier IR32517 and seven NCP302155 55A MOSFETs.
Below are closeups of the power bits, Samsung GDDR6, and the control ICs.
Below is a screenshot of GPU-Z showing the clocks we achieved at stock speeds. Out of the box, the MERC308 BLACK RX 6600 XT has a listed game clock of 2428 MHz, with the boost clocks to 2607 MHz. The card ran fairly consistently near 2600 MHz.
XFX Speedster MERC308 BLACK RX 6600 XT on the test bench…
Test System and Benchmark Methods
|Test System Components
|ASUS ROG Maximus XII Extreme, ASRock Z490 PG Velocita
|EK Predator 360 AIO
|2×8 GB G.Skill Royal 3600 MHz CL16-16-16-36
|Gigabyte Aorus 2 TB NVMe Gen4 (OS + Applications)
|EVGA 750 W G3
|XFX MERC308 BLACK RX 6600 XT / Adrenalin 21.7.1
Our test system is based on the latest mainstream Intel z490 platform and uses the i9-10900K 10/20t CPU. The CPU is overclocked to 4.9 GHz on all cores/threads, with the cache set to 4.3 GHz. The clock speeds used will provide a good base to minimize any CPU limitations on our titles, particularly when using the lower resolutions, and should be attainable with a good air cooler or better. The DRAM is in a 2×8 GB configuration at 3600 MHz with CL16-16-16-36-2T timings, middle-of-the-road option balancing performance, and cost.
Since the last update, we have made some significant changes adding a few new titles and dropping some of the older games. More details can be found in the GPU Testing Procedure article, which we have updated with our latest benchmarks. Below is a quick summary for easy reference.
- UL 3DMark Time Spy – Default settings
- UL 3DMark Fire Strike (Extreme) – Default settings
- UL 3DMark Port Royal – Default Settings (Ray Tracing capable cards only)
- Unigine Superposition – Performance, 1080p High
- Shadow of the Tomb Raider – DX12, “Highest” preset
- The Division 2 – DX12, Ultra preset, VSync Off
- Assassin’s Creed: Odyssey – Ultra High preset, VSync Off
- Far Cry New Dawn – Ultra defaults
- F1 2020 – DX12, Very High defaults, TAA, and x16 AF, Australia track, do not show FPS counter.
- Metro: Exodus – DX12, Ultra defaults
Our first set of benchmarks hail from Underwriters Laboratories, which acquired Futuremark back in 2014. Earlier in 2018, a rebrand occurred, and since that time, Futuremark is now UL. The benchmarks have not changed, just the name. We chose to stick with 3DMark Fire Strike (Extreme) and 3DMark Time Spy as these tests give users a good idea of performance on modern titles.
3DMark Fire Strike (Extreme) is a DX11-based test that runs at 1080p resolution. UL says the graphics are rendered with detail and complexity far beyond other DX11 benchmarks and games. 3DMark Time Spy is a DX12 benchmark designed for Windows 10 PCs. It supports new API features such as asynchronous compute, explicit multi-adapter, multi-threading and runs at 2560×1440. 3DMark Port Royal is the first Ray Tracing benchmark designed for Windows 10 PCs and graphics cards with Microsoft DirectX Raytracing capabilities.
Looking at the charts above, we see the XFX MERC308 BLACK RX 6600 XT is quite a bit faster than the RTX 2070 in 3DMark’s Fire Strike Extreme and in Time Spy once overclocked. The RX 6600 XT falls behind all the RTX cards in Port Royal, a Ray Tracing benchmark, but this is expected with AMD’s first attempt at hardware-based Ray Tracing. Just as Fire Strike Extreme seems to be AMD-friendly, Unigine’s Superposition is the opposite, with the XFX MERC308 BLACK RX 6600 XT slipping between the RTX 2060 and RTX 2070.
We have updated our testing suite for gaming benchmarks to bring more modern titles into the mix. Gone are Battlefield V, F1 2018, Far Cry 5, AOTS:e, and World of Tanks, which have been replaced with Metro Exodus, Assassin’s Creed: Odyssey, F1 2020, and Far Cry: New Dawn. We kept The Division 2 and Shadow of the Tomb Raider. The games should provide a good view of the card’s overall performance. Many of these are DX12 games.
1920 x 1080 (1080p) Results
The XFX MERC308 BLACK RX 6600 XT runs between the RTX 2060 and the RTX 2070 throughout most of our testing, aside from Far Cry: New Dawn and Assassin’s Creed: Odyssey, where results appear to be hamstrung by the CPU at the lower resolution. Looking at Shadow of the Tomb Raider and F1 2020, the overclocked XFX MERC308 BLACK RX 6600 XT was nipping at the RTX 3060 Ti’s heels trailing only by a few FPS.
2560 x 1440 and 4K UHD Results
Below are the higher resolution results starting with 2560 x 1440 and the gaining in popularity 3840 x 2160 (4K UHD). These resolutions prove to be a bit of a stretch for lower-end cards, but the XFX MERC308 BLACK RX 6600 XT proves it is capable at 2560 x 1440 WQHD.
Moving up in resolution, the gap tightens; the XFX MERC308 BLACK RX 6600 XT is trading blows with the RTX 2070 at both resolutions. The RX 6600 XT’s super-high clocks help to keep it in the fight. Our 4K UHD results show the XFX MERC308 BLACK RX 6600 XT isn’t quite up to the task at the highest quality presets we test with. At the middle resolution of 2560 x 1440, we maintained 60 FPS, making this a solid choice for gaming at WQHD.
Ray Tracing and DLSS Testing
Below, we tested Metro Exodus and Shadow of the Tomb Raider with ray tracing on at 1440p and 4K. The XFX MERC308 BLACK RX 6600 XT proved it could not render Ray-Tracing at these resolutions with the quality set to maximum.
We didn’t have results to compare with Nvidia’s DLSS since AMD’s version, FidelityFX Super Resolution, is still in development, but it is supposed to accomplish similar results.
For those unfamiliar with Folding@Home, it is a project originally started by Stanford University, but it is now based out of Washington University in St. Louis. Their goal is to help create treatments and cures for various diseases by understanding how human proteins “fold” or misfold, which is where the name comes from. This is done by simulating the folding of human proteins requiring enormous amounts of computational horsepower. This is where everyday people like you and I come in by donating our PC resources to fold at home during our spare time.
Currently, the folding@home team is working on various treatments, but one that is on everyone’s mind these days is Covid-19. There’s a whole list of diseases that they work on, such as Cancer, Huntington’s, and Parkinson’s, to name a few, with the option to select which you would like to donate your time to.
We have team 32 here at Overclockers.com with members who can answer questions and help you optimize your folding if you’re interested in this.
We have a couple of screenshots of the XFX MERC308 BLACK RX 6600 XT folding project 16959, a Cancer-related protein. As you can see, it folds approximately 400,000 PPD and uses 100 W doing so. We have also included an example of the types of proteins they work on.
Mining for Cryptocurrency isn’t really my thing, but we felt it might interest our readers with the market today. The following example is using NiceHash, which has a built-in benchmark. The XFX MERC308 BLACK RX 6600 XT is running stock without any type of optimization. As such, with GPU alone, it could earn you about USD 2.14 per day using 102 W.
With a small amount of tweaking, such as reducing the GPU core speed and voltage while upping the speed of the 8 GB of GDDR6, we were able to make some nice gains. The hash rate is now up to ~ 33 MH/s while only using 73 W of power, and you’ll also notice the temperature is quite low at 41°C.
Overclocking the XFX MERC308 BLACK RX 6600 XT
MSI Afterburner is now working with AMD 6000 graphics cards. While it did work previously, we found through testing that AMD’s Radeon software delivered more consistent results as MSI AB allowed the core speed to drop significantly more, resulting in lower scores. XFX also has two presets programmed into the BIOS, which can be set with the Adrenalin tuning software.
We used the “balanced” preset, which was recommended for testing. There is also a “quiet” setting with a slightly lower power limit and a higher fan target temperature junction keeping the fan rotation to a minimum even though the balanced setting was still super quiet.
For overclocking, we used AMD’s Radeon software. The interface is very similar, but overclocking the new Navi GPUs are slightly different. Instead of a fixed maximum clock for the GPU core, you need to set a lower and upper range. This took some testing as setting either range too high would diminish results or cause the benchmark to fail. We settled on an upper range of 2766 MHz and the lower range of 2636 MHz; the software maintains a minimum of 100 MHZ between the upper and lower ranges. Setting the lower range too high forced the upper range up as well, which proved to be unstable in some benchmarks. At these settings, the XFX MERC308 BLACK RX 6600 XT ran consistently around the 2750 MHz mark, which is quite impressive using stock cooling and showcases AMD’s RDNA2 architecture. We also added 140 MHz to the memory speed to finish our overclocked settings.
The XFX card peaked at 2761 MHz and consistently ran at that speed through some of our benchmarks but settled around 2750 MHz during Time Spy. This shows the variance in overclocking the new NAVI 23; the core speed is very dependent on the load. In the end, this took our Time Spy score of 10,239 and raised it to 10,862, showing about a 5% increase which was consistent throughout most of our benchmarks.
Temperatures and Power Use
We test power consumption by running through the game benchmarks of Shadow of the Tomb Raider and F1 2020 at stock speeds and while overclocked. We monitor temperatures throughout this testing, with the peak temperature listed in the data below. The benchmarks are extended (time) to allow the card to settle to simulate real gaming conditions more accurately.
Temperatures on the XFX MERC308 BLACK RX 6600 XT peaked at 70°C in F1 2020 and 74°C SOTR at stock settings. After overclocking the card, temperatures increased slightly in each game, peaking at 75°C in F1 2020 and 76°C in SOTR. These are great results and demonstrate just how well XFX’s cooling solution works. The fans ramped up slowly, then settled at 50% when overclocked, and were barely audible over the rest of the system.
Power use for the XFX MERC308 BLACK RX 6600 XT peaked at 304 W (system total power) at stock, reaching 318 W while overclocked (both in SOTR). For most systems, a quality 550 W power supply will be adequate for your needs, even while overclocking both the card and CPU.
XFX’s MERC308 BLACK RX 6600 XT takes AMD’s reference design and improves it in every way. The MERC308 version comes equipped with a 6+1+1-phase power delivery system and 225 W of available power from the one 8-PCIe connectors. The heatsink is effective and quiet with an appealing appearance overall. The XFX MERC308 BLACK RX 6600 XT is only 274 mm (10.7″) long, making it suitable for small form factor builds. Always check your dimensions before purchasing. The drawback to having these features is a meager price increase. The reference model AMD RX 6600 XT’s MSRP is $379, XFX’s MERC308 BLACK will run you $420 at Newegg, a modest increase of $40 over the reference MSRP.
What does that look like compared to other cards? The XFX MERC308 BLACK RX 6600 XT at $420 is in the ballpark compared to most aftermarket RX 6600 XTs and is more affordable than many others (if you can find one in stock). For example, the MSI Mech RX 6600 XT @ $560, and the ASUS ROG Strix RX 6600 XT @ $550 at Newegg.com, and are currently sold out. As you can see, prices among the comparable competition are higher than the XFX MERC308 BLACK RX 6600 XT, but these prices are clearly not the MSRP but an inflated value due to the current graphics card market. If you can find one at the MSRP, the $420 price tag looks reasonable in comparison. Otherwise, we expect this card to end up where the others currently are.
Considering the market today and pricing on graphics cards in general, $420 doesn’t seem excessive for a premium solution RX 6600 XT. XFX has done a great job with the XFX MERC308 BLACK RX 6600 XT and is worth considering if you have the money to spend. Here at Overclocker’s, we have no qualms giving it our seal of approval!
– Shawn Jennings (Johan45)