Calculate the bus bandwidth needed to display a VGA (640x480) true-color movie at 30 frames/sec. Assume that the data must pass over the bus twice - once from the CD-ROM to memory, and once from the memory to the screen.
I'm not sure if it's HW or not (sounds odd to be a HW assignment)...so I'll just be vague.
Calculate the number of pixels you have (you gave that value already), do you know what true-color represents? The number of bits per pixel is likely to be either 24 or 32-bits (just stick with 32-bits, as that's easier to deal with). Well, if you're passing it over twice, what do you think you'll have to do to the numbers? I don't think this is entirely accurate though, as I think that it takes more than two trips 'round.
24-bits is "true color" for this problem.
24 bits per pixel for 650x480 is 7,372,800 bits per frame = 921,600 bytes per frame.
at 30 frames/second thats 27,648,000 bytes per second.
but, how does the cd-rom to memory and memory to screen have to do with anything?
Thanks for the help!
This is all going to depend on your bus topology, but assuming a non 'hub' design, it would go something like this.
1) CD-ROM to RAM via PCI 33MHz, 32bits wide, SDR. to memory bus 100/133MHz, 64/128bits wide, SDR/DDR
2) RAM to CPU via system bus 100/133MHz, 64/128bits wide, SDR/DDR/QDR
3) CPU to Video RAM via System to AGP bus 66MHz, 64bits wide, SDR
4) Video RAM to RAMDAC
Of course there are overheads..... calculating those is the hard part. If you start getting into ECC and single bit error correction it could take you a few years to read through all the white sheets to locate that information.
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