Radeon RX 7800 XT and 7700 XT launch notes

2023-09-06

I don’t own one, I’m just writing down my thoughts on reading the launch coverage. (I’m particularly looking at these reviews: TechPowerUp 7800XT, TechPowerUp 7700XT, igor’sLAB, GamersNexus 7800XT, and GamersNexus 7700XT.)

Radeon Anti-Lag+ is a new game feature equivalent to Nvidia’s Reflex. I hate that these exist in the first place (the problem these are made for really ought to be fixed in game engines in a GPU-agnostic way, and if GPU manufacturers think it reasonable to do this in the first place it’s a reflection of other problems), but since Reflex does exist and certain game developers consider using it to be an acceptable alternative to fixing their own tech it’s a fair thing for AMD to have their own solution. Unfortunately, RAL+ is still not generic and only works on RDNA3.
FSR 3 Fluid Motion Frames is here, competing with Nvidia’s DLSS 3 Frame Generation. These both suck. It doesn’t matter who’s doing it or what tricks they’re trying to make it better, this approach necessarily increases latency. They’re not entirely useless, but 98% of their usefulness is in marketing rather than real gaming.
The performance gap between the 7700XT and 7800XT is generally a bit bigger than the price gap, making the 7800XT generally the better value option. This goes double if you want to use it with a 4K monitor, as the 7700XT’s 48MB of L3 cache is pretty cramped beyond 2560x1440.
The 7700XT’s full-load power use (about 230W) isn’t much lower than the 7800XT’s (about 250W), but under partial load the 7700XT maintains a significant efficiency lead. This makes sense because the VRAM, memory controllers, and in this case probably some other components on the MCDs don’t scale down their power use so cleanly as the compute units, so in partial loads having 25% less of the not-so-scalable stuff is a solid win.
As the 7700XT clocks a bit higher than 7800XT in practice, the 7800XT can’t actually bring that much more compute power to bear, and most of the performance difference is from L3 cache size and VRAM bandwidth.
Transient power draw is reasonably well controlled; these aren’t too rough on power supplies. A 650W power supply should be comfortable for the vast majority of builds with these.
In non-raytracing work the 7800XT performs similarly to (on average a touch better than) a 6800XT or 4070 while costing $500 against the 4070’s $600. Versus Nvidia this is good, but the 6800XT already was (at the prices of the last couple months), and the 7800XT is only a very small step forward from the 6800XT in performance per dollar. For $450, the 7700XT’s performance lands squarely between the above cards’ and the $400 4060Ti 8GB’s. Again, this is a solid performance per dollar win versus Nvidia, but nothing groundbreaking otherwise.
The 7800XT makes some decent efficiency progress over the 6800XT (including apparently under partial load, which is interesting given the challenges associated with chiplets), but is still behind the 4070 at this, drawing around 250W fully loaded against the 4070’s 190-200W.
This is always a bit fuzzy, as a lot of relevant information isn’t available, but it looks like a 7800XT and a Navi 21 based card (like a 6800XT or 6950XT) probably cost roughly the same to produce. (TSMC N5 is quite a lot more expensive per wafer than N7.) This work AMD has put into chiplets should still be very valuable over the next few years given where lithography looks like it’s going, but for this generation it doesn’t appear to be working any miracles for AMD’s manufacturing costs.