The MGA prototype defined an AGP memory allocator (albeit a weak one) which in turn allowed glReadPixel to exceed 800MB/s. That was a few years ago, and I would guess new chipsets and graphics cards could double that.
but it is rare that image read back is the best solution. However, when it is, proper us of AGP makes a significant difference. A prototype was done in open source for the Matrox G400 driver, but was never maintained. There were more recent discussions on DRI-devel to bring this functionality back, here is a pointer to the thread: http://www.geocrawler.com/mail/thread.php 3?subject =%5BDri-devel%5D+proper+ioctls+%28%3F%29++to+expor t+agp+to+a+user&list=680
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The MGA prototype defined an AGP memory allocator (albeit a weak one) which in turn allowed glReadPixel to exceed 800MB/s. That was a few years ago, and I would guess new chipsets and graphics cards could double that.
but it is rare that image read back is the best solution. However, when it is, proper us of AGP makes a significant difference. A prototype was done in open source for the Matrox G400 driver, but was never maintained. There were more recent discussions on DRI-devel to bring this functionality back, here is a pointer to the thread:p 3?subject =%5BDri-devel%5D+proper+ioctls+%28%3F%29++to+expor t+agp+to+a+user&list=680
http://www.geocrawler.com/mail/thread.ph