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Nvidia Announces RTX 4090 Coming October 12, RTX 4080 Later
Since the Nvidia hack back in February, we've had a decent idea of what we might expect from Nvidia's RTX 40-series Ada Lovelace GPUs. Early figures put the maximum number of Streaming Multiprocessors (SMs) at 144 for AD102, though we wouldn't expect Nvidia to launch with a fully-enabled GPU right off the bat.
Today, during the GTC 2022 keynote (which you can view in its entirety on YouTube, though the "good stuff" starts at the 6:03 mark and runs until about 24:32), Nvidia CEO Jensen Huang revealed the specifications for the RTX 4090 and RTX 4080, along with details of the Ada Lovelace architecture. Most of the most recent leaks appear to have been reasonably accurate.
Core counts and clock speeds (estimated to be within about 10 MHz based on Nvidia's official teraflops figures) are all basically known at this point. The RTX 4090 will have 128 SMs with a 2,520 MHz boost clock, coupled with 24GB of GDDR6X memory running at 21 Gbps with a 384-bit interface. The memory configuration basically looks unchanged from the RTX 3090 Ti, which on the surface is basically correct. However, much like AMD did with RDNA 2’s Infinity Cache, Nvidia will apparently be packing 96MB of L2 cache in AD102, compared to just 6MB of L2 cache in GA102 — that’s not yet officially confirmed, but we see little reason to doubt it at this stage.
Core counts receive a greater than 50% boost over Ampere, with 128 SMs instead of only 84 SMs maximum — and there’s still room for a 140–144 SM model in the future, perhaps a new Titan RTX, or at least a future RTX 4090 Ti. Core counts alone would provide a big jump in performance, but Nvidia has also tuned Ada to reach higher clocks, again similar to what AMD did with RDNA 2, and the result is the expected 2.5–2.6 GHz boost clocks on the announced models. That’s nearly 50% more than the RTX 3090’s 1,695 MHz boost clock and 35% higher than the RTX 3090 Ti’s 1,860 MHz — and Jensen says that Nvidia has hit clock speeds in excess of 3.0 GHz with overclocking in its labs. (Hello, 800W custom RTX 4090 cards!)
Combined, the GPU shader counts and clock speeds yield the theoretical maximum performance figure. RTX 3090 was rated at 35.6 teraflops, RTX 3090 Ti bumped that up to 40 teraflops, and now the RTX 4090 pushes the needle up to 82.6 teraflops — more than double the compute, in other words. While teraflops alone can be a somewhat meaningless figure, it’s still useful within similar architectures, and we’re looking at perhaps the largest generational jump in performance that we’ve seen from Nvidia since the GeForce brand first came into being.
It's not just RTX 4090, either, though some will undoubtedly be unhappy with the launch prices for the RTX 4080 16GB and RTX 4080 12GB models. Yes, much to my chagrin, Nvidia will have two different 4080 SKUs separated by memory capacity. Based on the specs alone, these will deliver wildly differing performance levels, probably larger than the gap between the RTX 3080 Ti and the RTX 3080 10GB. Of course, the price difference should make it immediately clear which model you’re buying, with the 16GB card starting at $1,199 and the 12GB model starting at $899. On paper, it looks as though the 16GB card will deliver about 20% more performance, give or take.
Nvidia hasn't stated which GPUs specifically are used in the various cards, though previous rumors suggested we were looking at three separate chips: AD102, AD103, and AD104. That still seems likely, again considering the differences in core counts, though it's possible the 4080 12GB will use harvested AD103 chips — if not now, then at some point in the future.
Note that Nvidia hasn’t specified a launch date for the RTX 4080 cards. We’re hopeful they’ll still arrive in October, or perhaps early November at the latest. Given AMD now plans to announce RDNA 3 GPUs on November 3, that sets a pretty firm time limit. We’ll probably see RTX 4080 GPUs arrive right before whenever AMD’s RX 7900 XT retail launch occurs.
The bigger question will be real-world gains, of course, and the lack of substantial gains on memory bandwidth does raise some flags. However, keep in mind that when AMD basically slapped a bunch of L3 cache onto its RDNA design and then boosted clock speeds, cards like the RX 6600 XT were able to stay ahead of the previous generation RX 5700 XT, which had nearly twice the memory bandwidth — and that was with only 32MB on Navi 23. 96MB of L2 cache should give Nvidia cache hit rates of 50% or more, which means the effective memory bandwidth is doubled.
