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zipless

V poor performance from system memory

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Some background: I''m working on a 2D game engine and i''ve got a rather scrappy 2D shooter running to test my functions and make it a bit more fun as well. I recently sent a copy to one of my friends before realising there might be problems, he''s running an old p200 or something like that with an *unknown* amount of video memory. Now i''m thinking that since this is a 2D engine i shouldn''t have much problem getting it to run, admittedly i''ve been greedy with memory so far but i should be able to trim back here and there or dump the surfaces to system memory. Thats where i come up with a problem. I''ve tried placing all the surfaces in system memory, bliting them to a secondary surface in sys mem then bliting that to the primary surface in vid mem. It constantly gives me rates of around 20 fps compared with 1200 fps when everything is in video memory. I''m bliting less than 100k in system memory and it''ll be a 600k or 1.2 meg blit to the primary surface depending on 16 or 32 bit colours (droping to 16 gives me 25-30 fps). Without performing a blit to the primary surface the frame rate rises to between 150 and 200 fps. I''m really confused here guys, i guess that there is some overhead when transferring to the vid mem from the system memory but i don''t know what exactly it is or how to bypass it. Any help would be appreciated, cheers guys

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