On 10/5/2014 6:17 AM, Valeri Galtsev wrote:
John, I would respectfully disagree. The bad thing about "shared" memory video cards is fundamental in the architecture. They use as video RAM a portion of main RAM, that means they place the video traffic (30, or 60, 50 25 frames per second multiplied by number of pixels worth) onto memory bus. This traffic has nothing to do with anything but the screen and just doesn't belong there. It is logically independent on anything and should be kept separate from memory bus - physically. I mentioned single board computer I soldered for my kid back then based on Z80 processor as an example of how rudimentary is to mix video traffic into memory bus. It was OK to do that on trivial amateurish single board computer. It is awful to step that low from architecturally good dedicated video ram away on modern sophisticated computer. My computer science degree rejects that and asks to take from "inventors" of that away their computer science degrees.
the Z80 had maybe 2MB/sec of memory bandwidth (thats off the top of my head before coffee). A Z80 system rarely had over 64K of ram, usually static, btw.. the DDR3 on a Intel i5-4570 (random upper midrange cpu I picked) has 25.6GB/sec memory bandwidth. a typical 1920x1080 display is 2Mpixels, at 24 bit/pixel and 60Hz LCD refresh rate, thats 360MB/sec to refresh the display. almost *nothing* compared with that 25GB/sec bandwidth. lost in the noise (half of the .6, to be more specific).
-- john r pierce 37N 122W somewhere on the middle of the left coast _______________________________________________ CentOS mailing list CentOS@xxxxxxxxxx http://lists.centos.org/mailman/listinfo/centos
