[Beige] Re: High Resolution With 16 colors?

[steve@dosius.zzn.com (Dosius)]

dempson@actrix.gen.nz (David Empson) wrote in message news:<1frblzf.chatqvrnuvv2N%dempson@actrix.gen.nz>...
> Bryan Parkoff <BParkoff@satx.rr.com> wrote:
> >     Think about the earliest resolution on IBM PC.  IBM PC had only 160x100
> > resolution with two colors.  It had 4x4 pixel font for 40/80 columns.
> > Please correct me if I am wrong.

720x350x2, not direct pixel-accesible, 9x14 font (MDPA).
CGA font was 8x8.

> 
> I don't know the details of anything which predates CGA.
> 
> CGA supports 4 colours (either of two sets) at 320x200, and two colours
> (white in combination with any of the sixteen colours) at 640x200.
> 
> Don't forget that CGA was designed to be used with a digital RGB
> monitor, while the Apple II (which predates it by at least three years)
> was designed to work with a television.  Completely different beasts.

Original IBM CGAs do have CVS video jacks on them.

> 
> >     Why did IBM PC only show 4 colors (black, white, blue, violent) on
> > 320x200 resolution and another 4 colors (black, white, yellow, green) on
> > another 320x200 resoltuion.
> 
> Because the data representation of the image only had room for two bits
> per pixel in 320x200 mode (one bit per pixel in 640x200 mode).
> 
> > Apple II's high resolution allows to combine 8 colors together.
> 
> Well, six colours, and don't forget that the effective colour resolution
> for hi-res graphics mode is only 140x192.
> 
> If CGA supports a 160x200 mode, then it could have four bits per pixel
> and 16 colours anywhere on the screen.

As in the PCjr/Tandy 1000 160x200x16 mode.

There is a hack that allows 160x100x16 on a CGA but it modifies 80x25
text mode to 80x50 with only half of the font, and uses characters 221
and 222 to produce graphics.  Lots of wasted space, but functional.

-uso.