[Coco] Rgb2vga improvements

[Steven Hirsch]

On Tue, 16 Sep 2014, Luis Antoniosi (CoCoDemus) wrote:

> Yep you could definitely use it but I don't know about the SDRAM specs. 
> I got it running in 229 Mhz on DE0-nano it it seems to work, despite the 
> datasheet said it operates in 133Mhz...

Is it possible that overclocking the memory is responsible for flickering 
pixels in graphics mode?

> But I don't do any refresh, it 
> writes and reads so fast that refresh is not needed and would certainly 
> impact the process.

That's interesting.  I guess the access is repetitive enough to do the 
trick.  Years ago I wrote assembly code for an embedded device that used 
an interrupt handler routine to step through a page of NOPs every 
millisecond or so.  There were no particular real-time constraints in play 
(it was a print buffer) and this saved some money on hardware.

Steve


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