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92 votes

Why were those colors chosen to be the default palette for 256-color VGA?

TL;DR: It's All About How To Look At the Palette That way it doesn't look any hideous and ugly, or does it? How Come? What is the origin of the default 256-color VGA palette? IBM's BIOS code :)) ...
Raffzahn's user avatar
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26 votes
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Why does PC video memory base address change depending on video mode?

The history behind the various base addresses is as follows: the area starting at A0000h was set aside for video frame buffers in general (see Who set the 640K limit?) MDA used 4KiB starting at ...
Stephen Kitt's user avatar
25 votes

Why were those colors chosen to be the default palette for 256-color VGA?

The VGA default palette in the 256 colour mode (Mode 13h) first has 16 color entries from CGA (which is also same as default 16-color EGA palette and the only palette for 320x200 EGA mode) Next 16 ...
Justme's user avatar
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20 votes
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What is the most accurate way to map 6-bit VGA palette to 8-bit?

The most accurate way of course depends on what is the purpose. No way is perfect and there is no one true method for all purposes. First of all, how the VGA works, is that it used the INMOS G171 ...
Justme's user avatar
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17 votes
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What are the blinking rates of the caret and of blinking text on PC graphics cards in text mode?

Yes, your hunch is correct. MDA, original card from IBM, reverse-engineered from schematics : The cursor blink signal is not handled by the Motorola 6845 CRTC. It is handled by dividing VSYNC with ...
Justme's user avatar
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15 votes

What is the most accurate way to map 6-bit VGA palette to 8-bit?

Justme detailed some of the reasons that the exact conversion method probably doesn't matter. Another reason is that you are probably going to interpret the 8-bit output according to the sRGB standard,...
benrg's user avatar
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14 votes

Why does PC video memory base address change depending on video mode?

TL;DR: Compatibility Before VGA there was MDA, CGA and EGA and it's all about continued support. But Why Different Memory Regions ? Video in the IBM PC is based on video cards bringing their own ...
Raffzahn's user avatar
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13 votes
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How do I stop flickering in mode 13h?

Yes, you need to synchronize framebuffer updates to happen so that the framebuffer area is not updated by your code while that area of framebuffer is being drawn on screen. Port 03DAh has bit 3 ...
Justme's user avatar
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8 votes

What is the most accurate way to map 6-bit VGA palette to 8-bit?

[Preface:That question isn't really related to retro computing but hardware in general, it might thus be moved] TL;DR: Absolute brightness on screen is not defined by the signal, but by the screen's ...
Raffzahn's user avatar
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8 votes

How do I stop flickering in mode 13h?

It depends on the details of the graphics card simulation on VBox, which in turn depends on which graphics mode you have chosen, but assuming you are interested in how it worked on legacy VGA, you ...
dirkt's user avatar
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7 votes
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RGBI direct connection to VGA display

For the actual questions, yes the overvoltage could cause damage, and yes you should use resistors. The problem is, TTL outputs are not meant to be connected to analog VGA inputs, not even with ...
Justme's user avatar
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6 votes

Is it possible to connect a modern monitor to an 1982 electrical typewriter?

For what it’s worth, the author of this Triumph-Adler BSM 100 SC video on YouTube calls it monochrome VGA monitor in the description. If it indeed is one, a color VGA display with no special support ...
Jukka Aho's user avatar
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6 votes
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Understanding the Need for Positive Sync Polarities in Sony PVM Monitors

Summary Do not connect H-sync and V-sync outputs together with a T-connector! (See below for more details.) Your Sony PVM requires negative-going composite sync, and positive-going sync will probably ...
cjs's user avatar
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6 votes

Why does PC video memory base address change depending on video mode?

For CGA vs. MDA, the reasoning for using different base adresses is simple and obvious: These two video systems are designed to co-exist for dual-monitor solutions thus each need a unique memory range....
tofro's user avatar
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5 votes

Were VGA palette's HSV math properties used in practice?

I don't think it's the same palette, but XCom/UFO used a palette composed of the same colors at different brightnesses so that it could do dynamic lighting with it. I think this may have been a ...
davolfman's user avatar
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5 votes

RGBI direct connection to VGA display

The TV set probably has some protection against overvoltage, but you shouldn't rely on it. Protection can suffer stress and eventually fail if you continuously run stuff out-of-spec like that. SCART ...
pndc's user avatar
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4 votes

Why were those colors chosen to be the default palette for 256-color VGA?

If I recall, it's the 16-color default palette, followed by 216 colors chosen as the combinations of 3 luminance values, 3 saturation values, and 24 hue values. Having 24 hues for all nine ...
supercat's user avatar
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3 votes

Understanding the Need for Positive Sync Polarities in Sony PVM Monitors

The service manual says the monitor has external sync defined as negative polarity, as expected from composite sync signals for standard 525/625 line TV scan systems, either from composite video input,...
Justme's user avatar
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3 votes

Understanding the Need for Positive Sync Polarities in Sony PVM Monitors

In older VGA monitors, both hsync and vsync polarity tells the monitor which size it has to zoom vertically. If you use the wrong combined sync polarity for a given vertical resolution the picture is ...
Janka's user avatar
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3 votes

Were VGA palette's HSV math properties used in practice?

I would believe the question is not really answerable the way it is. For one,the default palette is a manufacturer side offering, as such intended for low effort application, the ones that do not take ...
Raffzahn's user avatar
  • 224k
3 votes

9 pin D-sub to VGA or USB

2 rows 9 pins D-SUB 9 (or Cannon 9) connectors were used on PC for serial COM ports (RS232) and in even older days also for IIRC EGA/CGA monitor connection. My bet is that it's the serial port (you ...
Spektre's user avatar
  • 7,286
3 votes

What is the most accurate way to map 6-bit VGA palette to 8-bit?

I would use simple linear search to construct a conversion LUT with minimal error. Here is simple C++ code for conversion from 6-bit to 8-bit: uint8_t LUT[64]; int i,j,jj; float ai,aj,d,dd,di=1.0/63,...
Spektre's user avatar
  • 7,286
3 votes

Why were those colors chosen to be the default palette for 256-color VGA?

People may think of VGA as ugly now, but considering what came before it, it offered much more flexibility than most previous home computer color implementations. Those often offered 8 or 16 colors ...
RichF's user avatar
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2 votes

What is the most accurate way to map 6-bit VGA palette to 8-bit?

The general formula, as given by OP, is actually the most exact: This formula describes the (obvious) idea that the most black color component keeps being the most black, and the most saturated ...
lvd's user avatar
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1 vote

9 pin D-sub to VGA or USB

The fact that Windows thought it was a mouse is a really good sign, and likely means that things are nearly working properly. First of all, there's no way that Windows would mistake a USB serial port ...
Sneftel's user avatar
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