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[patrik_osgnach]

Hi. I'll soon start an university project abotu GPGPU so I proposed my professor to do something with OpenCL. I currently own a hd4870 video card and I just wanted to know how good this card is in doing opencl stuff

[himanshu_gautam]

patrik.osgnach,

OpenCL's beta version is supported on HD 4870.

So you can implement most of the openCL stuff on it.

[patrik_osgnach]

Ok, I was worried because on wikipedia in 4870's page opencl was not listed among supported APIs

you said "most of the stuff", what will I miss?

[MicahVillmow]

patrik,
HD4870 has OpenCL 1.0 support with no extensions or image support. There are also performance issues with local memory due to hardware constraints.

[liuk]

Hi, MicahVillmow

Can you be a little bit more specific on the local memory issue of HD4870? I'm currently working on this card and I find my programs run generally slower after I made the "Local memory optimization". Thanks in advance.

[nou]

local memory is emulted in global memory. 5xxx card have fast local memory on chip. 4xxx have local memory on chip too but there is some restriction about read/write access which do not conformnt wth OpenCL.

so using local memory on 4xxx is same as using global.

[MicahVillmow]

local memory on 4XXX is a owner's write model, not a generic read/write model. What this means is that each thread can write to its own memory, but read from any other memory. This is too restrictive to work with OpenCL, so we do not implement it.