Details about Nvidia's next-generation graphics architecture weren't supposed to be out this early. However, Acer's Kepler-equipped Aspire Timeline Ultra M3 notebook has already made its way onto the market in some parts of the world, and there are a couple of reviews out already. AnandTech and PC Perspective have coverage of the M3 notebook and its GeForce GT 640M GPU, although most of the details about the chip remain a closely guarded secret.
Here's what we know. The mid-range GeForce GT 640M has 384 ALUs, four times the number in the GT 540M it will presumably replace. Kepler appears to be much denser than the old Fermi architecture, at least based on those core counts. While the old part's ALUs ran at 1.34GHz, the 640M is clocked a little lower, at 1.25GHz. Both chips sport 128-bit memory interfaces and run their RAM at 900MHz. In Acer's new notebook, the 640M is joined by an even gigabyte of video memory.
PC Perspective says the GeForce GT 640M is designed to offer a "playable experience at 1366x768 with high detail settings in all of the most demanding titles released last year." The site's performance data seem to validate that claim; Battlefield 3, Batman: Arkham City, Skyrim, and Deus Ex: Human Revolution all boast average frame rates in the 37-74 FPS range. The rest of the performance results are from laptops with different CPU configurations, so it's hard to tell how the new GeForce really measures up to other mobile GPUs.
The 15.6" Timeline Ultra M3 is thin enough to fit into the ultrabook category, so the fact that it has a discrete GPU is impressive in itself. However, the system reportedly gets pretty toasty, with the center of the bottom panel reaching 128°F (53°C) under heavy gaming. The slim chassis may be more to blame than the GPU there, because the Timeline Ultra actually looks to have quite good battery life overall.