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124 votes
Accepted

What character is the MS-DOS cursor?

The text-mode cursor isn’t a character, it’s managed separately by the video output circuitry (which is how it keeps blinking even when your computer is busy or locked up). It can be enabled or ...
Stephen Kitt's user avatar
94 votes
Accepted

Why do PCs boot in 720x400 resolution?

This is historically not uncommon at all. Before starting an Operating System and initializing a graphics mode, your PC operates in the simplest display mode available, 80×25 text mode. The original ...
StarCat's user avatar
  • 1,465
83 votes

Why were CLIs typically light text on dark background, whereas GUIs typically use(d) dark text on light background?

Why did early CLIs seemingly so predominantly use light on dark color schemes, and what drove the shift to GUIs using dark on light color schemes instead? Simple: CRT technology (and, as so often, ...
Raffzahn's user avatar
  • 224k
78 votes
Accepted

How did old MS-DOS games utilize various graphic cards?

Did every programmer of every game implemented all possible various API's that old graphic cards supported? Yes - but it went even deeper than that. Early graphics cards had virtually no callable ...
Greg Hewgill's user avatar
  • 6,999
71 votes
Accepted

Reason for the Amiga clock speed

The architecture of most "color computers" of the 70s-80s was very tightly built around the NTSC color video standard. Almost all of them had a 14.31818 MHz crystal. Note that this is four times ...
Harper - Reinstate Monica's user avatar
67 votes
Accepted

Why was video, audio and picture compression the poorest when storage space was the costliest?

TL;DR Computer processing power/speed/cost and storage density/cost have been moving at roughly the same pace for 50+ years. There are of course variants, where either CPU speed has increased much ...
manassehkatz-Moving 2 Codidact's user avatar
65 votes

Why didn't early color TV sets accept RGB input?

When colour television broadcasts began (1960s, in the UK; perhaps a little earlier in North America?) there weren't any local devices that customers might want to use. Broadcast TV was the only ...
Toby Speight's user avatar
  • 1,676
62 votes

Why did the VIC-20 and C64 have only 22 and 40 columns when the earlier PET had 80 column text?

One reason was likely that the VIC-20 and C64 did not have their own displays, but were designed to be connected to a television set. The interface between the computer and the television was not ...
Greg Hewgill's user avatar
  • 6,999
60 votes

Why were some early PC 3D cards unsuitable for 2D graphics?

Early high-performance 3D accelerators such as the Voodoo Graphics have limited framebuffer resolutions (640×480 for most Voodoo Graphics configurations, 800×600 for the Voodoo2 in non-SLI) and colour ...
Stephen Kitt's user avatar
56 votes

How did the Atari 2600 achieve a resolution of 160 x 192 pixels with only 128 bytes of memory?

The 2600 didn’t have a frame buffer. Instead, programs running on it had to draw the picture on the screen pretty much in real time. This actually had some advantages on a low-cost system. Each line ...
Stephen Kitt's user avatar
55 votes
Accepted

What determines the color of every 8th pixel on the Apple II?

A nice one - and coming up every now or then. TL;DR The Apple IIs video logic produces a B&W bitstream at the right frequency to bedazzle an NTSC TV set in a way to make it 'see' colour. The ...
Raffzahn's user avatar
  • 224k
54 votes

What character is the MS-DOS cursor?

The cursor on the CGA, MDA, EGA, and VGA cards was a hardware sprite generated on the earlier cards by the 6845 video controller, and on later cards by a chip that emulates the 6845. That chip has an ...
supercat's user avatar
  • 36.4k
50 votes

In the classic "Windows 98 crashes live on CNN" video, why does the BSOD appear so oddly?

VGA graphics and text modes have different scan rates. The Windows desktop runs in some graphics mode (looks like 640x480, likely 60 Hz) while the BSoD is in text mode (720x400 at 70 Hz). The adapter ...
Zac67's user avatar
  • 3,904
48 votes
Accepted

Which font with slashed zero is being used in this screengrab?

The font in use appears to be the ‘9×14’ bitmap font (i.e. 8×14 glyph bitmaps tweaked for 9×14 character cells) of the Hercules graphics card. The title of the video is ‘Windows1 (1985) PC XT ...
user3840170's user avatar
  • 23.1k
42 votes

Why was video, audio and picture compression the poorest when storage space was the costliest?

You mean beside that all these algorithms had to be designed, implemented, rolled out and accepted first? Which of course would only happen as a need was developed to use them? Well, that may leave ...
Raffzahn's user avatar
  • 224k
40 votes

Why did some video games apparently use "interlaced" video modes?

Indeed, early devices such as C64, NES, or IBM PC with CGA adapter did not use interlacing, but simply sent 240p to the TV. And later devices such as the Amiga could send either 480i or 240p. But TVs ...
Justme's user avatar
  • 32.6k
39 votes
Accepted

How did the Amiga DCTV work

After some research, I found the hardware engineer that built the DCTV and we exchanged some messages where he explained the system. This is the unedited text: Wow, it has been a long time... I didn'...
Thomas's user avatar
  • 3,842
39 votes
Accepted

How did the Sega CD decompress video?

We used to have to write our own video playback system, so each game did it differently. I worked on Microcosm for the SegaCD and if I recall we used a 16 colour palette for the video playback and had ...
Martin Linklater's user avatar
39 votes
Accepted

What mid-1970s to mid-1980s home computers had their graphics characters added to Unicode 13?

The new additions mentioned are mostly to be found in the new Symbols for Legacy Computing block (PDF link) covering the 1FB00–1FBFF codepoint range. This block includes: a large number of BLOCK ...
natevw's user avatar
  • 2,947
38 votes
Accepted

Commodore 64 to modern TV

The VIC-II chip inside the C64 computer outputs a S-Video signal, which is mixed and modulated into the matal box that contains the UHF modulator circuit. Earlier models made composite video available ...
mcleod_ideafix's user avatar
37 votes
Accepted

How did the Atari 2600 achieve a resolution of 160 x 192 pixels with only 128 bytes of memory?

According to wikipedia, the Atari 2600 had a resolution of 160 x 192 pixels. had it been monochrome, it would had needed 160*192 = 30,720 bits of video RAM, or 3,840 bytes. Even more taking colour ...
Raffzahn's user avatar
  • 224k
36 votes

Why would any "local" video signal be "interlaced" instead of progressive?

nothing but a clever way to save data bandwidth by only sending every other line There's more to the story. Interlaced video originates with CRT televisions. Standard analogue television is always ...
RETRAC's user avatar
  • 13.7k
35 votes

Why did computer video outputs go from digital to analog, then back to digital?

Early digital video outputs, like CGA, were not really akin to the later standards such as DVI and its follow-on's. The reason for using multiple lines to carry the different analog portions of the ...
Brian H's user avatar
  • 60.8k
31 votes

Why did the VIC-20 and C64 have only 22 and 40 columns when the earlier PET had 80 column text?

Use of TV as monitor is the reason for these low resolutions. The issue is that the color resolution of TV is very low. While B&W TV could resolve pixel small enough for ~400 to ~600 pixels, color ...
Patrick Schlüter's user avatar
30 votes

How were the special effects achieved for the Kraftwerk Die Roboter 1978 music video?

It may be helpful to note that this is not a live recording but a pre produced video. These are pretty standard analogue (post production) effects at the time. Including real mirrors, two cameras and ...
Raffzahn's user avatar
  • 224k
29 votes
Accepted

What are the differences between a PAL and NTSC C64?

Hardware-wise, the Commodore 64, like most early computers, was synchronized to its graphics output: in the case of the C64, the CPU clock was derived from the timing crystal in the video hardware. ...
Mark's user avatar
  • 8,585
29 votes
Accepted

Graphics chips in 1980

There were. A couple of examples are the Motorola MC6845 and the MC6847. These chips were flexible and allowed various resolutions and colors depending on how they were implemented. The MC6845 was ...
Tim Locke's user avatar
  • 4,811
29 votes

How did old MS-DOS games utilize various graphic cards?

Early on, you had to explicitly code your game for each graphics card you wanted to support: Hercules, CGA, Tandy, EGA, VGA. You had to know how to put the card into graphics mode and you had to know ...
snips-n-snails's user avatar
28 votes
Accepted

Why did the TRS-80 CPU have priority over the display?

Why did they instead give the CPU priority? It's the lowest effort solution. It needs no additional hardware (*1). At the same time it's a transaction safe solution. Whatever the CPU writes gets ...
Raffzahn's user avatar
  • 224k
28 votes
Accepted

Why did 1990s-2000s LCD all use 60 Hz refresh?

To be fair, cost, need, and usefulness of anything above the standardized 60 Hz minimum for different resolutions are the reasons why it took long for LCD monitors to go past 60 Hz. The LCD panels ...
Justme's user avatar
  • 32.6k

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