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CGA color fix for Olivetti M24SP

freakedenough

freakedenough

Experienced Member
Joined
Jul 30, 2016
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94
Location
Vienna, AT
Hello,

I faced the following problem with my Olivetti M24SP: in text mode (mode bw80 and mode co80) light gray looks like low blue.
this results in unreadable texts in some programs :-( can anyone help me with this? I'm using the original Olivetti CGA Card and monochrome monitor.


VirtualBox_DOS_04_08_2016_12_20_42.jpg WP_20160804_12_16_41_Pro.jpg
 
The 'blue' attribute on a CGA corresponds to 'underlined' on an MDA. The M24 has a second mode select register at 03DEh, and when bit 6 of this register is set, characters with a blue foreground colour appear as white underlined characters.
 
So, theres no fault in my hardware, just incompatibility to the original CGA? Is there a way to override that?
 
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It sounds like the sort of setting that could be changed either by motherboard DIP switches, or by some sort of DOS utility. But I don't know the M24 well enough to know if either of those facilities has been provided.
 
There is no jumper or switch to change anything in this direction: http://www.olivettim24.hadesnet.org/docs/tecman.pdf
Meanwhile I've created a CGA-VGA adapter to get an 8-color-mode (CGA without intensity) on my flat TV. Foreground (text) blue is white and underlined text.



Here I've selected blue as foreground (text) color and black as background color:

If i would have selected blue foreground and light gray background you wouldn't be able to read anything > both seem to be white

Here I've selected light gray as foreground (text) color and blue as background color:




I hope someone who also has an Olivetti M24 can help me with this.
 
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Back when I used an M24 with a monochrome monitor (mine was the AT&T 6300 variant), I avoided the problem entirely by running MODE BW80 before running any program that couldn't reconfigure its color set.

However, I don't remember running into that problem very much; in fact, running MODE CO80 usually made everything display properly as shades of gray. Are you using AT&T MS-DOS 2.11 or 3.x, or some generic MS-DOS version? If the generic version, your MODE command might not be aware of the M24's display hardware.
 
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