EGA Latched graphics

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tuxie
Less than a nibble
Posts: 1
Joined: May 7th, 2022, 1:18 pm

EGA Latched graphics

Post by tuxie »

Hi. I am making a pretty bodged port of the reverse engineered Cosmos Cosmic Adventure source code (https://github.com/smitelli/cosmore/)

Things are going reasonably well. I managed to wrap my head around how the EGA planar graphics works.

But the latched ega graphics is giving my head some issues. From what I have read, writes to the memory is supposed to be copied across all of the planes. But how does that work? (Example: https://github.com/smitelli/cosmore/blo ... l.asm#L317)

If it copies the same data across all the pages, won't the exact same data be in all the planes, making it effectively black and white? Obviously that's not a thing that happens, so I am.. slightly confused.

Add to that the notion of a 'draw page' that you can see in that source. Are there more than one place you can write graphics data to that you can switch between, or.. ergh. My head :').

Any tips for where to find some non-brainmelting guides for ega graphics, or even some handholding would be pretty nice.
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MrFlibble
Forum Administrator
Posts: 1778
Joined: December 9th, 2010, 7:19 am

Re: EGA Latched graphics

Post by MrFlibble »

I suggest that you repost your question at VOGONS forums, there's almost no activity here nowadays. Sorry.
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