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Old 03 May 2016, 13:30   #217
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Join Date: Jun 2015
Location: Germany
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Originally Posted by kipper2k View Post
Due to the fact that the Vampire uses CPU power to provide HDMI output you would think it drains the CPU power but tests are showing (using the minibench) that at high Res there are still 90MIPS free for the CPU to perform other tasks.
This is worded a bit inaccurately. Of course, the hdmi part is totally independent of the CPU but -- just like the Amiga custom chips -- needs to read graphics data from the memory. Thus, the RTG modes take some bandwidth from the enormously fast on-board fastmem. This means that with RTG enabled the CPU sometimes will have to wait for the access to the memory because RTG DMA is prioritised (you wouldn't want to get random black sports on the screen under high CPU load, would you?). RTG DMA is buffered so that it can give priority to the CPU as long as the buffer isn't running too low which gives some memory bandwidth and thus lost speed back to the CPU. As kipper said the effect on CPU speed is quite low but it gets bigger with increasing screen resolutions and colour depths.
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