Meanwhile, the GDDR5 memory frequency has increased 50% from 4008MHz to a blistering 6008MHz.

By default, the GTX 680 comes clocked at 1006MHz - already 30% higher than the reference GTX 580 - with a dynamically changing Boost Clock of 1058MHz. Instead, everything now runs off the core clock, which now also features what Nvidia calls a 'Boost Clock,' a technology akin to Intel’s Turbo Boost. The GTX 680 ramps that up to a massive 1536 CUDA cores, 128 TAUs and 32 ROPs, bringing loads of horsepower to the race.Ī few changes have been made to the clock speeds while the Shader clock has been removed entirely. Based on Fermi's second-generation Streaming Multiprocessor (SM) architecture, the GTX 580 has 512 CUDA cores, 48 ROP (Raster Operations) units and 64 TAU (Texture Addressing Units). This refinement is visible in all aspects of the card, not least of which is raw performance. That's an improvement from the 40nm GTX 580, which has 540 million fewer transistors yet is almost three times larger, and it partly highlights the overall goal of Kepler: improved efficiency. Branded as the GeForce GTX 680, the card is powered by a 28nm GPU codenamed GK104 that crams 3540 million transistors into a 294mm2 die. The loss of the higher shader clock (presumably due to the power and heat constraints of so many stream processors) means that, in comparison to the GTX 580 1.5GB, each stream processor is actually running 5,44MHz (35 per cent) slower, although there are now three times as many of them.On March 22, Nvidia unveiled its first 'Kepler'-based graphics card. This is the same way that AMD’s GPUs have operated for years and is another example of the two companies moving in the same direction when it comes to GPU design. This means the whole GPU, stream processors and all, runs at a nippy base clock of 1,006MHz. Sadly, that’s not quite the case, as Nvidia has chosen to scrap the separate shader clock, long a defining feature of its GPUs. With so many more stream processors than its predecessor and an otherwise similar GPU layout, you’d be forgiven for expecting a quite extraordinary threefold increase in performance. The scheduling functions themselves have also been redesigned and greatly simplified with a greater focus on power efficiency.

This doubles the GPU’s instruction per clock rate in comparison to Fermi, necessary when there are so many more stream processors to address. The number of Warp Schedulers (the part that assigns render threads from the Gigathread engine to individual SMs) has doubled to four per SM (although the total number on the GPU remains 32) and each is now able to dispatch two instructions per clock thanks to a pair of instruction dispatch units for every Warp Scheduler. This huge increase in stream processor count to 1,536 for the whole GPU (tripled in comparison to the GTX 580 1.5GB’s 512 stream processors) has required some extra additions to each SM. The new SMs, dubbed SMX (presumably Nvidia is competing with AMD’s ‘GCN’ for silliest GPU lingo 2012) have been completely redesigned, and now boast a whopping 192 stream processors each, as opposed to the 32 stream processors found in each SM with Fermi. Each GPC still contains its own raster engine, but it’s within the SM that the real changes have been made. Click to enlarge - The Kepler Architecture and a side-by-side comparison of Kepler's SMX and Fermi's SMĪs with Fermi, the GPU is split into four separate graphics processor clusters (GPCs), but each is now comprised of just a pair of SMs rather than four SMs apiece, in a similar fashion to the GTX 560 Ti 1GB's GF114 GPU.

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