Re: DHGR Video Riddle Solved!!!

["Arkain" <rwking@usa.nospam.net>]

OK. Let me help you out a little...

"Jeff Blakeney" <CUTblakeney@home.com> wrote in message
news:39b7d929.238888600@24.9.0.17...
> On Wed, 6 Sep 2000 17:05:33 -0500, "Arkain" <rwking@no.usa.spam.net>
> wrote:
>
> Well, I just tried all three of your programs on my IIgs, which has an
> RGB monitor so is free of colour bleeding, and all three programs
> produced a colour display and I could only get colour pixels
> regardless of whether the high bit of a byte was set or not.

The IIgs, as far as I know, only uses mode 2. This is not surprising since
that's the only mode documented in the IIe technical reference manual.

> Whether this is a difference between the IIgs and the IIe, I don't
> know.  If you want I can set up a IIe on the weekend and try those
> programs on it with my AE Ramworks II card as my extended 80 column
> card but I still don't see how it can possibly work.  There is no way
> for software to turn off the colour burst crystal on the composite
> output of a IIe so I don't understand how a IIe could possibly output
> any kind of monochrome image without special hardware.

Like I said before: The color burst signal is never turned off in DHGR
mode... at least not on a composite monitor. This leaves the screen with 560
color-bleeding horizontal dots. Depending on the position of the dot, it
seems you'll still get some subset of the 14 colors, but in a dot that's 1/4
the size of the normal DHGR pixel. This means that it will normally appear
that the screen is still in full color mode when it's not.

> By the way, I'm only aware of one DHR mode.  560x192.  The number of
> colours you get depends on whether you view it on a colour or
> monochrome monitor.  If viewed on a colour monitor, you will get 16
> colours but if you view it on a monochrome monitor, those 16 colours
> appear as different dot patterns and you can see all 560 horizontal
> dots.

The easiest way to tell the difference is to populate the screen with 80
column bit-mapped text. Each block, 1 byte wide & 8 rows tall, should be
used to make a character. In mode 1 you'll be able to read whatever text you
put on the screen, but you won't be able to predict the colors using the
mode 2 method. In mode 2, the text will be harder to read, but the colors
will be just what you expected.

As for mode 3, the proof of it is in the fact that games like Test Drive
display text clearly on a IIe, but blur the text with extra color blocks on
a IIgs. If the mode were strictly mode 2, then the text would always show
with color on the edges.

Arkain