[Coco] A Technical Question

[Mark McDougall]

On 21/05/2012 1:12 AM, Steve Bjork wrote:

> As for your statement "*In theory, there's no real limit to the resolution
> or colour depth if you're re-generating the screen in an FPGA.*" is very
> questionable.
> There is always a limit. Because of the speed of the memory systems, you can
> not go faster than the read and write speed of the texture map memory and
> the display buffer. There are many other limits like the Math Processor that
> plots the source of the texture data and the screen location to draw.

That was my statement Steve. What I meant was, if you're generating the 
video in an FPGA within a cartridge, then the Coco hardware itself places no 
restrictions on the resolution you can *in theory* produce.

It goes without saying that your hardware has limitations; the memory 
bandwidth and Fmax of your FPGA design determine the maximum resolution. Our 
last video design, for example, is capable of mixing two 24-bit streams up 
to 1920x1080p, but it requires DDR3 and an expensive FPGA running a video 
processing core around (IIRC) 165MHz.

But, as you point out, there's little point connecting all this video power 
to a 1.79MHz 6809...

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"