View Full Version : fast pbo with ,nvidia
07-12-2005, 01:15 PM
I need to speed up my pbo with a P4 computer and a xeon computer... Is there any opinion about fast memcpy that we can use with pbo on windows compiling with visual c++ 2003. Is it a good idee to use memcpy_amd with intel architecture?
07-13-2005, 04:29 AM
You can try to use glBufferSubData call instead of
Driver can be optimized to detect CPU and decide which internal memcpy to use for mem transfer.
In my video player test app, changing from Map/memcpy/Unmap sequence to glBufferSubData produce lower average CPU time (2-5%).
If you want to do readback, you can use glGetBufferSubData instead of Map/memcpy/Unmap sequence. There is a bit speedup.
Test benches on my test machine (NV 6800GT, FW 76.45, P4-3.2/HT):
Map/memcpy/Unmap = 476 MB/sec
glGetBufferSubData = 484 MB/sec
07-13-2005, 10:21 AM
If you want to perform fast memory copy, use MMX instructions with prefetch reading and non-cashed writing(MOVNTQ instruction if I'm not mistaken). AMD has a paper on it. Notice that it only has sence with very large memory regions, at least 100Mb
07-13-2005, 02:01 PM
Does mmx etc. operations have any meaningful application in connection with memory-mapped vertex/pixel-buffers? I would assume they were only useful for system-memory transfers?
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