[Coco] Re: CoCo to SVGA

[John Kowalski]

At 08:09 PM 30/10/2004 EDT, CoCoList for Color Computer Enthusiasts wrote:
>In a message dated 10/29/04 2:40:15 AM Eastern Daylight Time, 
>Torsten at Dittel.info writes:
>
>> You're right. If not so, I'd be able to program an interlaced mode
>>  doubling the vertical resolution by flipping video pages. However, I
>>  heard that Sockmaster was able to do something like this on a CoCo3
>>  using a bug of the early GIMEs (I just tried it on a CoCo2).
>
>Neat trick -- even lines in one image page and odds on another!
>But creating the split image would be a pain (well, splitting a given image 
>file would be easy, but drawing lines and circles in real time would be, ah, 
>interesting.
>--Mike K.

Oh, by the way, depending on what horizontal resolution you would want to be
running in, you wouldn't actually have to split the image into two pages at all.

By using the GIME's 256-byte wide "virtual" screen mode, you could set it up
so that only the first 128 (of every 256) bytes display during odd frames,
and the 2nd 128 bytes display during even frames.

So, visibly, and internally, the whole interlaced screen could still be
addressed in one single logical segment.

This would limit your horizontal resolution to 128 bytes per scan line, but
that still gets you up to 256x450 in 16 colors, 512x450 in 4 colors, or
1024(640 visible at a time)x450 in 2 colors.

The GIME is just full of little effects that can be abused---I mean, taken
advantage of.  :)

                                         John Kowalski (Sock Master)
                                         http://www.axess.com/twilight/sock/