AMD Radeon RX 6600 XT Review: The Memory Compromise

The AMD Radeon RX 6600 XT is a product of the times, delivering a reasonable overall package, but with somewhat lackluster specs and performance given the price. It's by far the most expensive 'mainstream' part we've seen so far, though such discussions are basically meaningless in the wake of ongoing GPU shortages. Look at our GPU price index, and it's obvious that anything worthy of being on our list of the best graphics cards will end up selling out, and then it will get scalped on places like eBay. MSRP or SEP (suggested etail pricing) will only impact a small fraction of people — those lucky enough to snag a card directly from AMD or Nvidia (BestBuy) at the 'official' price. However, most cards will end up selling at whatever price the market dictates, and sadly that means far more than AMD's nominal $379 launch price for the RX 6600 XT.

The Navi 23 GPU that powers the RX 6600 XT makes some interesting compromises as well. Normally, we'd expect to see a trimmed down Navi 22 part by this point in the life cycle, but either yields are so good that AMD doesn't have enough chips to launch something like the previously rumored Radeon RX 6700, or it's saving those harvested GPUs for something else (laptops). Navi 22 has a maximum configuration of 40 CUs, 12GB of GDDR6 on a 192-bit memory bus, and 96MB of Infinity Cache. Navi 23 still has 32 CUs, a relatively small reduction, but tops out at 8GB of GDDR6 on a 128-bit bus with only 32MB of Infinity Cache — AMD even cuts the PCIe interface to x8 Gen4, which is technically the same bandwidth as x16 Gen3, but if you're on a Gen3 board you get half the interface bandwidth. That results in a significantly smaller die size of 237mm^2 compared to 335mm^2 on Navi 22 — a 29% reduction. 

The problem is that all the trimming of the fat will inevitably affect the flavor of the steak. In addition, while the computational performance of the RX 6600 XT looks good — it's only about 20% lower than the RX 6700 XT — the reduction in memory bandwidth and capacity, as well as L3 cache, will also reduce performance. We'll see just how far in a bit, but the RX 5700 XT will be an interesting point of comparison, considering it has significantly more bandwidth but runs on the original RDNA architecture.

It's AMD's own fault for pushing VRAM capacities with earlier RX 6000 series launches. When Nvidia launched the RTX 3080 with 10GB VRAM and then kept the RTX 3070 Ti, RTX 3070, and RTX 3060 Ti at 8GB, AMD effectively made a statement with the RX 6700 XT, RX 6800, 6800 XT, and RX 6900 XT that 8GB simply wasn't sufficient. Of course, that's not entirely true, but there are certainly games and settings that will now have issues on GPUs that 'only' have 8GB of memory — games promoted by AMD, not surprisingly.

We'd argue that 8GB is still reasonable for mainstream options in our GPU benchmarks hierarchy, but then we run into problem number two: AMD has given the RX 6600 XT a price that's arguably more for the bottom of the high-end market than for a mainstream GPU. With the closest competitor being Nvidia's RTX 3060 12GB that offers 50% more memory as well as a theoretically 13% lower price, the RX 6600 XT might be a reasonable option, but it's not a clear winner by any stretch.

Architecturally, Navi 23 sticks with the same general formula as the other Big Navi and RDNA2 GPUs. It comes with DirectX Raytracing (DXR) support and implements the full DirectX 12 Ultimate features list, including Variable Rate Shading (VRS), mesh shaders, and sampler feedback. But AMD says the 32MB of Infinity Cache was chosen specifically for the target 1080p gaming audience, and we've seen in the past that higher resolutions tend to benefit from more L3 cache. That means while the RX 6600 XT should certainly do well at 1080p, it may not scale as well to higher resolutions like 1440p and 4K.

We're still more concerned with the 128-bit memory interface, though. That gives the RX 6600 XT exactly half the bandwidth and memory of the RX 6800 XT, with a quarter of the L3 cache. Will that mean half the performance as well? And what does that look like against competing GPUs from both Nvidia and AMD — and not just current generation cards, but also the previous generation?

These are good questions, though the most important question will be how many GPUs AMD can manufacture and get to the market. There's plenty of evidence that Nvidia currently outsells AMD by a ratio of at least 10-to-1 (based on the latest Steam Hardware Survey, as well as our GPU pricing index data), and that could boil down to production capacity. RX 6600 XT performance won't matter much if gamers can't go out and buy the card. 

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