NVIDIA GeForce GT 640M: Kepler Goes Mobile

Introduction and Specifications

Typically mobile graphics launches trail their desktop counterparts by a few months, as major GPU players like NVIDIA and AMD wring out power consumption and performance from their architectures in order to accommodate the tighter thermal and power budgets of notebook form factors. However, NVIDIA has obviously been refining their new Kepler GPU architecture into its various incarnations for while now, because the company is launching a dual salvo of production silicon for both mobile and desktop graphics markets today.  Of course the company has significant motivation for this, with Intel's Ivy Bridge mobile platform just around the corner, backed with DX11 class integrated graphics.

The fact that NVIDIA is ready with both desktop and mobile variants, in and of itself, is fairly impressive but their mobile platform demonstration vehicle may also surprise you.

An Ultrabook with a discrete graphics chip?  The Acer Timeline Ultra M3 sports NVIDIA's latest.

NVIDIA presented us with a 15-inch Acer Ultrabook to show off their midrange mobile chip based on their new GeForce 600M series architecture.  It's just 20mm thin, weighs about 5lbs and claims to offer up to 8 hrs of battery life, though you can bet that figure is not under a gaming workload.

Regardless, NVIDIA obviously decided to step out in current fashion and is looking to up the "ultra" factor in Ultrabooks. Although it seems like an unlikely place for a discrete GPU, NVIDIA's 28nm Kepler design trimmed down to "only" 384 processor cores and a 128-bit memory interface, sips a lot less power than its higher-end desktop counterpart.  Of course, the Acer Timeline Ultra M3 is also a bit larger than most of the 13 and 12-inch Ultrabooks we've looked at thus far as well.  But it's still a pretty svelte and light machine.

Let's look at the specifics of the NVIDIA's new GeForce GT 640M mobile graphics engine...

NVIDIA GeForce GT 640M
Specifications & Features

With a graphics core clock of 625MHz and a 384 CUDA core architecture, you might think the GeForce GT 640M is a higher-end chip, but NVIDIA has a few other higher-end members of the family flanking this one.  At this point, the GeForce GT 640M is the closest successor to the company's previous generation GeForce GT 555M. 

Here's a quick look at NVIDIA's new notebook graphics product stack:
GeForce 610M

GeForce GT 620M
GeForce GT 630M
GeForce GT 635M
GeForce GT 640M LE
GeForce GT 640M
GeForce GT 650M
GeForce GTX 660M
GeForce GTX 670M
GeForce GTX 675M

As you can see, there's a GeForce 600M series now in all segments, but not all are based on the new Kepler architecture.  Here's what a few of the GeForce GT 600M series GPUs look like, beyond the GeForce GT 640M we'll be stepping through today...

NVIDIA GeForce GT Performance GPU Specs

GeForce GT 650M GeForce GT 640M

GeForce GT 640M LE

GeForce GT 635M
Process 28nm 28nm 28nm 40nm 40nm
Architecture Kepler Kepler Kepler Fermi Fermi
Processor Cores Up to 384 Up to 384 Up to 384 Up to 96 Up to 144
Processor Clock Up to 850MHz Up to 625MHz Up to 500MHz Up to 762MHz Up to 675MHz


Up to 2GB


Up to 2GB


Up to 2GB


Up to 2GB


Up to 2GB GDDR5
Memory Width Up to 128-bit Up to 128-bit Up to 128-bit Up to 128-bit Up to 192-bit
Memory Bandwidth Up to 64.0 Up to 64.0 Up to 28.8 Up to 50.2 Up to 43.2

NVIDIA is blending some Fermi designs into the lineup, but re-branding them so as to limit confusion in product placement and performance.  However, there is a fair bit of Kepler technology through the top end of the stack.  NVIDIA's formal press release can be found here. Also, if you'd like a deep dive look into NVIDIA's new Kepler GPU architecture, we'd suggest heading over to our Geforce GTX 680 article for the full low-down.  Marco goes through all the heavy lifting and details there.

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