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M24SP DB25 to DB9 adapter

Chuck(G) said:
We've been here before. A CGA monitor at 400 lines isn't going to work. An EGA one will, however.
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An M24, M24SP, 6300, 6060, 1600 and M240 never has been shipped with a standard CGA monitor. So a standard CGA monitor is not relevant. These machines always have been shipped with the original olivetti or AT&T or Xerox monitors, which are optically modified M24 monitors. These original monitors are capable to display 640x400, monochrome or color.

By the way, you call it DEB, the original pocket guide calls it "Video Enhanced Adapter GO329" http://www.1000bit.it/support/manuali/olivetti/m24.pdf - maybe the naming difference between DEB and VEP comes from difference naming between AT&T and Olivetti.

Here @trixter confirms 640x400x16: http://www.vcfed.org/forum/showthread.php?61120-AT-amp-T-6300-high-res-color

An enhancement board was available that gave the 6300/M24 the ability to display 16 colors at the enhanced 640x400 resolution. This board was called the DEB (Display Enhancement Board), and had a few other tricks, like being able to display text pages and graphics pages at the same time through bitplane mixing.
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Later trixter links to this PDF, where the enhanced modes of DEB/VEP are described more in detail: ftp://ftp.oldskool.org/pub/drivers/...Guide AT&T Personal Computer 6300 GWBASIC.pdf , page 519 and following



View attachment 47457

Another posting of Trixter regarding M24 tipps: https://trixter.oldskool.org/2008/04/22/beefing-up-your-6300/

PS: Original color or mono monitor broken? The video output is analog, not digital, so you can wire up a VGA converter cable and use a VGA monitor.
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--> links to ftp://ftp.oldskool.org/pub/drivers/ATT/6300/video_converter_output_to_VGA.pdf , basically the same document as I linked above for the adapter.

But now you make me courious to check my M24SP if it has the DEB/VEP daughterboard. My M24SP also looks quite untouched, only one ISA slot used, no missing slot brackets. But to open the top cover, it's only two screws.
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Additional ressources:
- ftp://ftp.oldskool.org/pub/drivers/ATT/6300/Documentation/Olivetti M24-240 FAQ.html
 
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2icebitn said:
Yes you're right. 'Highlight' must be the intensity line, see how they're grouped together:

View attachment 47451

And incidentally I edited post 10. It should make sense now :)

Chuck's got this one. It's a digital monitor. I don't know what lead people to believe it was analog.
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Yes, sure, that's the signal which tells internally in the graphics card, if the color is displayed light or dark. But in the thory of operations manual we don't have the circuit diagram of the video dac behind this. Trixter and other sources don't warn, that the M24 only displays 8 colors on VGA monitors. I think he is accurate enough to warn if it would be a fact. So it's not.
 
2icebitn said:
Yes you're right. 'Highlight' must be the intensity line, see how they're grouped together:

View attachment 47451

And incidentally I edited post 10. It should make sense now :)

Chuck's got this one. It's a digital monitor. I don't know what lead people to believe it was analog.
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that means there is INTENSITY on pin7 and the PDF in my 1st post is wrong with NOTHING?

1ST1 said:
Trixter and other sources don't warn, that the M24 only displays 8 colors on VGA monitors. I think he is accurate enough to warn if it would be a fact. So it's not.
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im 100% sure that i followed the schemantic in the pdf. i have only 8 colors.


however guys im now totally confused if the output is digital or analoge and if it is possible to connect VGA with 16 colors or not.
 
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This intensity signal is not pin on the video connector. It is an internal signal on the graphics card to make it CGA compatible. Behind this signal there is some logics which combines the color information with intensity and this then is put to anaogque output.
 
could be also that theres something wrong with my config, i mean have a look:

ZZT game - blue background is underlined (also on original monochrome monitor)
20180820_164436.jpg 20180820_164516.jpg

olivetti's customer.exe shows clearly only 8 colors, intensity is missing on VGA but difference is visible on original monitor (note: colors are labelled as "gray")
20180820_164021.jpg 20180820_165340.jpg

i use olivetti dos 3.20 and its mode with co80.
customer.exe also says "monochrome video system"
 
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1ST1 said:
Yes, sure, that's the signal which tells internally in the graphics card, if the color is displayed light or dark. But in the thory of operations manual we don't have the circuit diagram of the video dac behind this. Trixter and other sources don't warn, that the M24 only displays 8 colors on VGA monitors. I think he is accurate enough to warn if it would be a fact. So it's not.
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'Highlight' is a pin on the video connector it would seem. If there are meant to be 4 video inputs to a color monitor, it's an RGBI output. Like a CGA monitor, or an NEC Multisync (in rgbi/digital mode). My 6300 is faulty, there isn't much I can prove or disprove at this point.
 
Ok, looking at the 6300 service manual, it states the Deb board can produce 16,536 colors, also allowing 2 monitors to be hooked up simultaneously. So perhaps w/o the Deb board the outputs are r,g,b,i, and the mode/I'd pins control all that. Pg 2-49.
 
Well I found a thread where someone asked the same question:
http://www.vcfed.org/forum/showthre...-(Olivetti-M24)-DB25-video-out-gt-CGA-monitor

Chuck(G) said:
According to the schematic at http://www.olivettim24.hadesnet.org/docs/m24schem.pdf, the intensity output is on pin 7. Always use the schematic as a reference

Good luck with the scan rate.
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Chuck(G) said:
The reason the VGA adapter shown on the M24 site is possible is because VGA color signal inputs are basically 0-0.7V analog, whereas the M24's outputs are, like MDA and CGA, TTL level (0-3+V) digital. So a simple cable will overdrive VGA inputs and you get no color gradation--everything's either off or on full-bore, so 8 colors (with one of them being black).

You could construct a simple circuit to take the M24 TTL-level and scale them to 0.7V full and something less (using the intensity output) to provide full 16-color VGA rendition. The problem is providing power for an active (best choice) circuit. The DC available at the M24 connector is 24V, which means that a voltage regulator would be required to drop it to 5V needed for standard logic. I suppose you could also derive a parasitic power source from the sync outputs.
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bobba84 said:
So that's why I only get 8 colours!
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Chuck(G) said:
The subject of VGA from the 6300/M24 was broached by the OP; in fact, the output diagram he cited was the one probably used by the VGA to D-sub 25 adapter on the cited web site. Hence, the diagram doesn't include intensity, even though it's on the DB25 connector, even though the schematic for the M24 clearly shows it--and, with the correctly-connected color monitor, the M24 can generate 16 colors.
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So INTENSITY is on PIN 7 and the PDF in my starting post is wrong (as it states NTH NOTHING which is not true).
The only reason why I cant build an adapter to my RGB CGA monitor is the scan rate of 25khz since the monitor supports only 15khz (CGA).
But does the Olivetti ALWAYS use a scan rate of 25khz, even on 320x240? Or 80x25 text mode? I would not use the Olivetti modes.
 
Let's start from zero. What's the characteristics of the monitor you've gotten output with? Do you have the specific specs on it? From looking on the web, it at least appears to be a cga monitor. Can't understand how it could be. And let's be perfectly clear, a "CGA" monitor is one that accepts r, g, b, I inputs, has a vsync of 15.75khz or close, and a vsync of 60hz. Use the IBM 5153 as an example. Most 80s monitors, except multisyncs, could accept 1 set of frequencies. Rarely do you have a monitor that can accept more then 1. So what exactly is your Phillips monitor, if you know?
 
2icebitn said:
Ok, looking at the 6300 service manual, it states the Deb board can produce 16,536 colors, also allowing 2 monitors to be hooked up simultaneously. So perhaps w/o the Deb board the outputs are r,g,b,i, and the mode/I'd pins control all that. Pg 2-49.
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That's bizarre - not 16384, but 16536? At any rate, the "Theory of Operation" manual, page 1-16, gives a little more detail. You're still limited to 16 colors, but there's a lookup table added, so you getcher choice of what those 16 are. Sort of like EGA. It also states that 3 more planes of 640x400 are added and that the extended attributes (blink, underline, etc.) are possible in (I assume) all modes.

None of which will do you any good unless you've got software that knows how to use the extra features. My guess is that such software is about as rare as Italian lutefisk. So you've got the basic 16 colors for just about everything. The second monitor would be nice, but again, you probably need some software for that.

Back-of-the-envelope time here. IIRC, the "white" level for VGA is 0.7V. The output of the 6300 display controller is probably within the range of 0.3 to 4.8V (driven by an 74LS244). So, to get 16 colors, you'd need to use the highlight signal to clamp the levels down to about 2.5V or less to get visible differences. You could also include "brown" correction for the "dim yellow" like the IBM CGA monitor does.
 
i am more interested in connecting the m24 to my cga monitor. is it possible in case i avoid the 640x400 mode? or is the line frequency alway 25khz?
 
freakedenough said:
i am more interested in connecting the m24 to my cga monitor. is it possible in case i avoid the 640x400 mode? or is the line frequency alway 25khz?
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hose philips monitors are made for CGA and PAL/NTSC video, fixed frequency (CGA timig is near to NTSC, but digital instead analogue signal). Your link always go to Commodore website, these monitors were popular with Commodore Amiga and Atari ST computers in color mode. It will not display 640x400.

I think the Olivetti is also fixed frquency, but it's timing should be closer to std vga. Unfortunatelly there is no spec of these monitors available, even not in the video units pocket guide I have.
 
Got a 'scope? Otherwise, I don't think so. I don't think a too-high horizontal sweep frequency will hurt a color monitor. The monochrome 5151 monitor (and its ilk) is a different matter.
 
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