Stream processors... what?

[rentaspoon]

So I have been waiting for the cash to buy a 270x and decided to have a look at the 260x and have noticed that clock and memory speed seems to be faster/equal on most cards but not by much. The only thing that's different is the stream processors so my question is what are they?

[Sundanc3]

They are effectively the computational units of the GPU itself. More units means more parallelism and faster computation times. Somebody else probably can explain it a whole of a lot better. 

 

AMD calls them stream processors, NVIDIA calls them CUDA cores

[Vitalius]

They are effectively the computational units of the GPU itself. More units means more parallelism and faster computation times. Somebody else probably can explain it a whole of a lot better. 

This basically covers it.

They are to a GPU what a CPU core is to a CPU. 

[simtransporter]

I believe they are comparable to cores on a CPU, the more of them you have the more things you can process in parallel. So when playing a game a stream processor can be used as a specific shader in order to render part of an image, the more stream processors the more you can render at the same time.

 

I'm not an expert in GPU architecture but that's how I understand it.

[Havoc]

So I have been waiting for the cash to buy a 270x and decided to have a look at the 260x and have noticed that clock and memory speed seems to be faster/equal on most cards but not by much. The only thing that's different is the stream processors so my question is what are they?

 

Quote from "zedx" on tomshardware.co.uk  -  Seems to explain it pretty well.

 

"A normal CPU is made up of multiple cores which can process different functions at the same time. For example you can run a compiler on one core and an encoder on another. These cores are very complex and process these functions at a very fast rate. Applications that can do several functions or threads at the same time can benefit greatly from this. Also these processors can perform a single function at an extremely fast rate. There are 4 and 2 cores in modern CPU's

Now stream processors perform a single thread at a very slow rate, I can't find data on how slow but it should be around 1/10 th of the speed of the CPU in a normal GPU. Anyways in Larrabee it is 1/2 the speed of a core 2 at the same clock frequency. But

GPU's contain hundred of these very simple processors which can make overall computation very high. However, different functions cannot be performed in at the same time in these stream processors. The same function can run on a very large set of data in these thingies. For example you can't run a compiler and an encoder at the same time but you can encode a large number of files at the same time. Of course you can also encode two files in two separate cores in a desktop processors, but overall it will be much slower than in a GPU. This type of parallelism is called SIMD (Single Instruction Multiple Data). Think of things that can benefit by doing the same thing on different sets of data. For example we have 3d rendering. You can use the same function to render 1000 frames in different cores.

The raw computational power of modern GPU's is 20x, i.e they can process about 1 teraflop while CPU's max do 50 Gigaflops. But this doesn't mean that there would be a 20x improvement in all tasks. For example, Nvidia and AMD launched Avivo and Badaboom media encoders and these provided about 4x the speed of a CPU. With better drivers and and opencl we can expect a 10x improvemet in a lot of things like rendering and then there's larrabee too."

 

Source: http://www.tomshardware.co.uk/forum/262638-33-stream-processors-help

[LIGISTX]

Basically, the more of them = the more power you have at your disposal as people have said. The speed (such as say a 1 ghz 290x) or something, is the speed at which these run at if I am not mistaken. So, the more of them running at a higher speed = more performance. Pretty simple. Every level of card you go up will have more stream processors, even sometimes more streams but slower speeds, but more of them outweighs more clock speed, for the most part anyways. Obviously 10,000 stream processors at 200 mhz might suck a little bit