Radeon RX 6600 XT put to the test: efficiency champion with full HD island talent

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The Radeon RX 6600 XT is the new smallest graphics card with RDNA 2. In the test it has to prove itself against the GeForce RTX 3060 and RX 5700 XT. Nobody is fooling you in the performance per watt discipline, but there are two special features to consider when it comes to performance: The memory and PCI Express interface.

Table of contents

  1. 1 efficiency champion with full HD island talent
    1. AMD's Radeon RX 6600 XT at a glance
    2. The technology: Navi 23, Infinity Cache, PCIe interface
    3. According to AMD specifications, it is 160 watts
    4. The MSI Radeon RX 6600 XT Gaming X in detail
  2. 2 clock rates, benchmarks (FHD & amp; WQHD) and ray tracing
    1. Test system, test methodology, games and drivers
    2. The actual average clock rates under load
    3. Benchmarks in 1,920 × 1,080
    4. Benchmarks in 2,560 × 1,440
    5. Benchmarks with ray tracing in Full HD and WQHD
  3. 3 Volume, temperature, power consumption and OC
    1. Volume & amp; Cooling
    2. Power consumption: games, YouTube, desktop
    3. Energy efficiency in FPS per watt
    4. Overclocking: a surprising amount of memory OC is allowed
  4. 4 PCIe 3.0 vs. PCIe 4.0, price and conclusion
    1. PCIe 4.0 or 3.0 makes a difference with x8
    2. RRP and market price
    3. Conclusion

AMD's Radeon RX 6600 XT at a glance

As a rule, a new generation of graphics cards comes first with the top models on the market, the smaller variants follow at a distance. It's no different with AMD's RDNA-2 architecture.

The RDNA-2 portfolio started with the high-end models Radeon RX 6800, Radeon RX 6800 XT (test) and Radeon RX 6900 XT (test) within a few days, followed by the middle class in the form of the Radeon RX after several months 6700 XT (test) and now with the Radeon RX 6600 XT an even smaller “entry-level solution”. Your application area clearly communicated by AMD at an RRP of 379.99 euros: AAA games in Full HD. Both the now two-year-old Radeon RX 5700 XT (419 euros RRP) and the GeForce RTX 3060 (329 euros) should be beaten.

  1. The MSI Radeon RX 6600 XT Gaming X in the test

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The MSI Radeon RX 6600 XT Gaming X in the test
Premiere for Navi 23 in the desktop PC

AMD implements the Radeon RX 6600 XT with the Navi-23 GPU, which up to now has only been installed on the mobile Radeon RX 6600M. ComputerBase uses an MSI Radeon RX 6600 XT Gaming X to determine whether the smallest RDNA-2 GPU achieves the goals set by the manufacturer – there will be no reference design this time.

But that's just the beginning, because with PowerColor Radeon RX 6600 XT Red Devil, Sapphire Radeon RX 6600 XT Pulse and XFX Radeon RX 6600 XT Merc 308, three other custom designs have already been created found in the editorial office. A comparison will follow shortly.

Model RRP at market launch Market launch GeForce RTX 3090 FE 1,549 euros September 24, 2020 GeForce RTX 2080 Ti 1,259 euros September 19, 2018 GeForce RTX 3080 Ti FE 1,199 euros June 3, 2021 Radeon RX 6900 XT 999 euros December 8, 2020 GeForce RTX 2080 FE 849 euros September 19, 2018 GeForce RTX 2080 Super FE 739 euros July 23, 2019 Radeon VII 729 euros February 7, 2019 GeForce RTX 3080 FE 719 euros September 17, 2020 Radeon RX 6800 XT 649 euros November 18, 2020 GeForce RTX 2070 FE 629 Euro October 16, 2018 GeForce RTX 3070 Ti FE 619 Euro June 10, 2021 Radeon RX 6800 579 Euro November 18, 2020 GeForce RTX 2070 Super FE 529 Euro July 2, 2019 GeForce RTX 3070 FE 519 Euro October 27, 2020 Radeon RX Vega 64 499 euros August 14, 2017 Radeon RX 6700 XT 479 euros March 18, 2021 Radeon RX 5700 XT 419 euros July 7, 2019 GeForce RTX 3060 Ti FE 419 euros December 2, 2020 GeForce RTX 2060 Super 419 euros July 2, 2019 Radeon RX 6600 XT 380 euros 11. August 2021 GeForce RTX 2060 369 euros January 7, 2019 Radeon RX 5700 369 euros July 7, 2019 GeForce RTX 3060 329 euros February 25, 2021

The technology: Navi 23, Infinity Cache, PCIe-Interface

With RDNA 2, the Radeon RX 6600 XT uses the same architecture and features as the larger RDNA-2 models, but the GPU used has a completely different footprint. The deployed Navi-23-GPU with 11.1 billion transistors consists of significantly fewer circuits than the larger offshoots (Navi 22: 17.2 billion, Navi 21: 26.8 billion), and the chip itself with 237 is accordingly mm² also much smaller. In contrast, production is again based on TSMC's N7P process.

On the Radeon RX 6600 XT, all 32 compute units of the Navi-23-GPU are active, which corresponds to 2,048 FP32-ALUs. That is 8 CUs less than the Radeon RX 6700 XT, but 4 more than the mobile Radeon RX 6600M. With a game clock of 2,359 MHz, even the smallest RDNA-2 offshoot offers a high GPU frequency, whereby the Radeon RX 6700 XT goes one better with 2,424 MHz. At 2,589 MHz, the maximum boost is even slightly higher than with the larger model.

The memory interface on the Radeon RX 6600 XT has a width of 128 bits (8 × 16-bit controller) compared to 192-bit or 256-bit of the larger models, the memory expansion is 8 GB of the GDDR6 type. Technically, 16 GB of memory would also be possible.

A small Infinity Cache with a lot (less) bandwidth

In connection with the 16 Gbps memory, the memory interface of the new graphics card offers a very small memory bandwidth of only 256 GB/s, the Infinity Cache is supposed to compensate (“buffer”) this in this case as well.

On the Radeon RX 6600 XT, however, it has also been massively shortened compared to the larger models, instead of 128 MB or 96 MB it is only 32 MB in size. According to AMD, this should still be sufficient for Full HD. In this resolution, the cache hit rate should be a little over 50 percent and thus be comparable to 128 MB in Ultra HD. In higher resolutions, the hit rate of the cache drops significantly compared to the larger models, so that the Radeon RX 6600 XT will probably break in more than the Radeon RX 6700 XT in WQHD – the test will clarify that later.

The Infinity Cache in RDNA 2 (Image: AMD)

Because the Infinity Cache on RDNA 2 is connected to the memory controller and there are eight on Navi 23, the 32 MB is made up of a total of eight 4 MB “chunks”. So not only are there fewer cache modules than on the larger GPUs, they are also only half the size.

The Infinity Fabric, to which, among other things, the Infinity Cache is connected, works on Navi 23 with a maximum clock of 1.8 GHz a little slower than the counterpart on Navi 21 and Navi 22, where a maximum of 1.94 GHz is available.

Eight controllers with 64 bytes/s each (1 controller per GDDR6 controller) are on board for the fast buffer storage, which with a total of 512 bytes/s is half as much as with Navi 21 (Navi 21: 1,024 byte/s, Navi 22 : 768 bytes/s). The bandwidth through the Infinity Cache is still a high 922 GB/s, which corresponds to about 19.5 Gbps memory on a 384-bit interface and thus the GeForce RTX 3090 – but only if the required data is available are in the 32 MB Infinity Cache. If this is not the case, they have to be accessed via the significantly slower GDDR6 memory interface.

The PCIe bandwidth is also significantly reduced

Apart from the previously mentioned reductions, AMD has also shut down the PCIe connection to the CPU on the small GPU; the computing power would not be large enough for the 16 PCIe 4.0 lanes active on the larger graphics cards. The PCIe 4.0 standard remains, AMD has halved the number of lanes. Even if eight PCIe 4.0 lanes may be sufficient for maximum performance, the full bus width can be an advantage if there is a lack of VRAM. In addition, there may be limitations if the substructure used only supports PCIe 3.0 (CPU/mainboard), because then the bandwidth, which has already been halved, is halved again. ComputerBase also clarifies in the test whether that costs performance.

160 watts are AMD specifications

AMD calls the Radeon RX 6600 XT a “total board power” of 160 watts, the TGP is 130 watts. Manufacturers can increase the power consumption of OC versions as usual, although it is to be expected that the custom designs will only add a little extra. At 160 watts, a single 8-pin power plug is provided for operation.

The Radeon RX 6000 models in comparison Radeon RX 6900 XT Radeon RX 6800 XT Radeon RX 6800 Radeon RX 6700 XT Radeon RX 6600 XT Architecture RDNA 2 GPU Navi 21 Navi 22 Navi 23 Process TSMC N7P Chip size 519 mm² 336 mm² 237 mm² transistors approx. 26.8 billion 17.2 billion 11.1 billion compute units 80 72 60 40 32 FP32-ALUs 5,120 4,608 3,840 2,560 2,048 RT acceleration Yes Game clock 2,015 MHz 2,015 MHz 1,815 MHz 2,424 MHz 2,359 MHz Maximum Boost clock 2,250 MHz 2,250 MHz 2,105 MHz 2,581 MHz 2,589 MHz FP32 performance 20.6 TFLOPS 18.6 TFLOPS 13.9 TFLOPS 12.4 TFLOPS 10.6 TFLOPS FP16 performance 41.3 TFLOPS 37.1 TFLOPS 27.9 TFLOPS 24.8 TFLOPS 21.2 TFLOPS texture units 320 288 240 160 128 ROPs 128 96 64 memory 16 GB GDDR6 12 GB GDDR6 8 GB GDDR6 memory speed 16 Gbps memory interface 256 bit 192 bit 128 bit memory bandwidth 512 GB/s 384 GB/s 256 GB/s Infinity Cache 128 MB 96 MB 32 MB IC bandwidth 2.0 TB/s 1.5 TB/s 0.92 TB/s L2 cache 4 MB 3 MB 2 MB TBP 300 watts 250 watts 230 watts 160 watts slot – Connection PCIe 4.0 × 16 PCIe 4.0 × 8 DirectX 12 Ultimate Yes RRP 999 euros 649 euros 579 euros 479 euros 380 euros

The MSI Radeon RX 6600 XT Gaming X in detail

With the Radeon RX 6600 XT Gaming X, MSI's premium model has arrived for the test. The graphics card is based strongly on the in-house Radeon RX 6700 XT Gaming X, differences can only be found in the details. Both cooler and equipment are not identical, but are very similar.

The MSI Radeon RX 6600 XT Gaming X looks quite powerful for an entry-level graphics card, which is primarily due to the 2.5 slot wide cooler, which is identical in structure to the counterpart on the larger model and only differs in the number of heat pipes and differs slightly in width. The latter is slightly narrower with the mentioned 2.5 slots compared to the 2.7 slots, and there are only four instead of five heat pipes.

  1. Power connection of the MSI Radeon RX 6600 XT Gaming X

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< img src = "/wp-content/uploads/9e0c6c4fc4a5a6e26dc9bc3a10dce1d3.jpg" /> Power connection of the MSI Radeon RX 6600 XT Gaming X
Monitor connections of the MSI Radeon RX 6600 XT Gaming X
Cooler profile of the MSI Radeon RX 6600 XT Gaming X
The back of the MSI Radeon RX 6600 XT Gaming X

The cooler structure, on the other hand, again consists of two different aluminum coolers, which are connected to one another by means of the heat pipes and are simply a bit flatter with the new 3D accelerator. The two axial fans with a diameter of 95 mm are completely identical. These switch off on the Windows desktop for silent operation.

There is a little OC and a little more TGP power by default

MSI calls the Radeon RX 6600 XT Gaming X a game clock of 2,428 MHz, the maximum boost is 2,607 MHz. That is 69 MHz and 18 MHz more than AMD's reference specifications. The TGP is 135 watts, which is 5 additional watts. Accordingly, an 8-pin power connector is also sufficient on the MSI hardware, especially since the TGP power can only be increased by a further 4 percent. There is no second BIOS with different clock rates and power limits.

With the Gaming X cooler known from the current generation, there is also a fairly simple RGB lighting, which is not a problem with an entry-level graphics card. The same applies to a simple look and feel, because there is nothing more than plastic, especially since it does not look high-quality.

Feature MSI Radeon RX 6600 XT
Gaming X Card PCB design MSI length, width 27.5 cm, 13.0 cm power supply 1 × 8-pin cooler design gaming X, 2.5 slots heat sink 4 heat pipes
Aluminum core/radiator Weight 882 g Fan 2 × 95 mm (axial) Fan switched off (2D) Yes Start-up speed 900 revolutions Clock
GPU base 2.064 MHz GPU average 2.428 MHz GPU maximum 2.607 MHz memory 8,000 MHz memory size 8 GB GDDR6 power consumption standard TGP 135 watts maximum TGP +4 percent connections 3 x DisplayPort 1.4 DSC
1 x HDMI 2.1

On the next page: clock rates, benchmarks (FHD & amp; WQHD) and ray tracing