The GeForce GTX series 260 GPUs

The GeForce GTX series 260 GPUs

NVIDIA last year launched the GeForce GTX series 200. The initial 65nm parts where big, really big, as they have roughly 1400 million transistors. It's actually the biggest chip that NVIDIA has ever build. To compare it: the GeForce 8800 GTX 'only' had roughly 700 Million processors. it was a bold move for NVIDIA to roughly double up on that previous transistor count.

Interestingly enough, that also doubled up the die-size of the processor and everyone expected NVIDIA to make the product at a 55nm fabrication process. They did not as the new architecture was still based on a 65nm fabrication size.

It took NVIDIA roughly half a year to move from 65nm towards 55nm, which was recently introduced. The entire GTX 260 is now based on a 55nm GPU. And if you read our articles on a regular basis, you'd have learned that the GeForce GTX 280 (65nm) is now being replaced by the GTX 285 (55nm).

But enough chatter on that topic. Let's walk through some of the main features (you need to stamp into your head). Obviously a big chunk of the transistors are being utilized for the shader cores. And shader cores the product surely has:

• 240 of them on the GeForce GTX 275/280/285.
• 216 cores on the GeForce GTX 260 Core 216
• 192 cores on the GeForce GTX 260

The shader architecture in the GTX 200 series is a work of art really, they have some cool features. Sitting in-between sets of shader cores for example now is an integration of local cache memory (16k software managed cache).

It is sitting in-between a block with 8 shader cores. So simply put, what helps here is that the data/instruction doesn't have to leave the GPU anymore to crunch it's data (normally in the regular frame buffer memory. This is a significant improvement in the architecture. You already spotted it, the new GeForce GTX 260 Core 216 has 216 Shader Processors (SPs).

Inside that GPU, the shaders cores are clustered in three blocks of eight shader processors. We know that there are ten clusters totaling up towards the 240 shader units for the GeForce GTX 280/285.  So the GTX 280/285 has 10x3x8= 240 Shader Processors. Therefore a standard GTX 260 has to have 8x3x8= 192 SPs.

The regular GeForce GTX 260 has got to have 8 shader clusters and thus 192 shader processors which you can utilize for gaming ... or computing other stuff.

What does this mean? Well:

• one shader cluster has 3x8=24 shader processors
• There are nine out of ten cluster enabled | 24x9=216 cores.

So the entire GTX 200 series is all one and the same chip. This new Core 216 GPU is in fact a full fetched GTX 280 core with one cluster laser-cut and deactivated. Check out the photo below.

GeForce Series 200 architecture - Look closely and spot the 10 shader clusters. On the GTX 260 Core 216 one has been disabled.

Other than the increased shader count, that should provide a significant boost to the shader compute power, other GPU denominators such as clock speeds remain the same. The GeForce GTX Core 216 SKUs will feature 72 texturing units and 28 ROPs. The updated GPU is technically called G200-103-A2 (the older core was G200-100-A2).The card still has a 448-bit (7x64-bit) wide GDDR3 memory bus with 896/1792 MB of framebuffer/memory. It comes with 1.0ns or lower memory chips.

So the extra 24 shader processor cores will give the SP216 versions of this product a little more bite. Especially in this price-range.

The reference clock frequencies for the 55nm parts of GTX 260 and Core 216 version remain the same, 576MHz on the GPU, and 999MHz for the GDDR3 memory. All that on a 448-bit memory interface. The power for the GTX 260 is fed by two six-pin connectors.