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 ...
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 ...
- 21k
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 ...
- 208k
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 ...
- 13.4k
28
votes
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 ...
- 27k
23
votes
Why was video, audio and picture compression the poorest when storage space was the costliest?
Compression == Expensive
To get an idea of what was considered an acceptable cost for compression, you should take a look at the PCX format, which was common for games and graphics programs of the DOS ...
- 564
21
votes
Accepted
How do 80x25 characters (each with dimension 9x16 pixels) fit on a VGA display of resolution 640x480?
How does VGA manage to show 720x400 resolution text on a 640x480 display?
This might be your basic misunderstanding here. Displays as used back then and what VGA was designed for, are not a fixed ...
- 208k
21
votes
How do 80x25 characters (each with dimension 9x16 pixels) fit on a VGA display of resolution 640x480?
CRTs don’t have a fixed pixel resolution; early CRTs have fixed timings (25.175 MHz and 28.322 MHz for VGA). VGA 80×25 text mode really does produce 400 lines of 720 pixels, as you determined, with a ...
- 117k
18
votes
Accepted
How to write text in MODE 0x13?
In mode 13h you can't write character codes to video memory because the card is not in text mode where it renders character codes to pixel data for you, it is in graphics mode where it just outputs ...
- 27k
16
votes
Why would any "local" video signal be "interlaced" instead of progressive?
As I had understood things, "interlaced" video was nothing but a clever way to save data bandwidth
Not really, it's a way to give more timely resolution, on TV 'half' pictures are not two ...
- 208k
15
votes
On my NES, the color red displays as black. What could be the cause?
Because the NES cartridge port uses a separate bus for fetching graphics data versus CPU code, dirty cartridge connectors can often cause graphical anomalies without otherwise affecting cartridge ...
- 34.1k
14
votes
Which font with slashed zero is being used in this screengrab?
According to the video's description the used graphics card is a Hercules Graphics Card. This type is as well what gets selected during installation at 2:36. Since the very same font is clearly ...
- 208k
14
votes
Why would any "local" video signal be "interlaced" instead of progressive?
CRT TVs basically understood one single SD video format which is sent over antenna (or cable) and that format is local to the geographic are you lived (NTSC, PAL, SECAM for most people). They did not ...
- 27k
14
votes
Accepted
Detecting if a video mode is supported by INT 0x10
Indeed, in many sources, the int10h subfunction AH=0 to set video mode returns without any meaningful status.
One way, suggested by C&T BIOS programming guide, is to verify if the mode is set via ...
- 27k
12
votes
Detecting if a video mode is supported by INT 0x10
That's not how you designed your programs in the early days of the PC:
You rather decided for one (maybe two) video cards (typically CGA and/or Hercules Monochrome) and then looked up your ...
- 32.4k
10
votes
Did any computer systems connect "terminals" using "broadcast"-style RF to multiplex video, and some other means of multiplexing keyboards?
The closest thing I know of is the IBM 2848 Display Controller in combination with IBM 2260 terminals. The 2848 generated, transmitted and stored video signals for up to 24 terminals. It did, however, ...
- 9,722
9
votes
What did game programmers and journalists mean by a "hardware trick"?
Some turned to hardware tricks to simulate 3D worlds, and the Super NES's Mode 7 could be considered a rudimentary form of texture mapping.
Note the following passage later on to give some context:
...
- 6,326
9
votes
Which font with slashed zero is being used in this screengrab?
We can see that the zeros are slashed, so it is probably not one of the 9x16 fonts which used to have dotted zeros.
Actually, that is the key clue. Dotted vs. slashed zeros were never specific to ...
9
votes
Why would any "local" video signal be "interlaced" instead of progressive?
A real CRT is a continuous drawing area. On a theoretical perfect CRT, the painting of each field would touch every point of the area exactly once, creating an evenly-lit and completely continuous ...
- 35.6k
8
votes
How do 80x25 characters (each with dimension 9x16 pixels) fit on a VGA display of resolution 640x480?
They don't fit to 640 pixels as VGA text mode is not 640x480.
640x480 is simply the one of the modes, but not the only mode available. It just happens to be the highest and most commonly known format.
...
- 27k
8
votes
Detecting if a video mode is supported by INT 0x10
BIOS has the ReturnFunctionalityStateInformation function 1Bh that can be used to retrieve a 20-bit bitmap of the supported video modes. You supply a far pointer to a 64-byte buffer that BIOS will ...
- 1,043
7
votes
Toshiba laptop with Windows 98 shows corrupted characters while booting, then the system goes entirely blind
This is not a full diagnosis, but one hypothesis can be formulated just from the screenshot.
It shows a setting from AUTOEXEC.BAT printed to the screen during booting. What the setting does is ...
- 21k
7
votes
What did game programmers and journalists mean by a "hardware trick"?
Magicians show magic tricks but it is not really magic as it only creates an illusion of magic because of some detail you don't yet know or have just not thought about it. So it's a trick.
Same ...
- 27k
7
votes
Accepted
How did the Dragon modify 6847 video output timing for PAL?
I used the redrawn schematics here on Github as it is difficult to read part numbers from the scans, and also it documents some detail quite well.
You are right that it does expand the line count to ...
- 27k
7
votes
Why did 1990s-2000s LCD all use 60 Hz refresh?
One benefit of high refresh rates on CRTs is to re-energize each phosphor more frequently, so decay between scans is less. And any pulsing of brightness happens at a frequency well above human ...
- 2,905
6
votes
Is it possible to chain TMS9918 chips to get better graphics?
Yes, the datasheet explains how to do it in section 3.5.
You need to share the clock and reset circuit. The two VDPs will then stay synchronized in an open loop (i.e. they’re both just counting cycles ...
- 2,220
6
votes
How to write text in MODE 0x13?
Graphics modes and text modes work entirely different to each other:
In text modes, the contents of video memory is expected to be character codes and attribute bytes. The CRT controller fetches a ...
- 32.4k
6
votes
How to write text in MODE 0x13?
There are no such ram locations in graphics mode, you cannot write text bytes and expect it to be visible in graphic modes.
The text you see in debugger is painted by the BIOS. When you use the BIOS ...
- 1,541
6
votes
Why was video, audio and picture compression the poorest when storage space was the costliest?
CPU/RAM decode performance, and engineering time to develop better compression algorithms and tune them. e.g. zstd in the last few years is like 10x faster than gzip, but compresses about as well. ...
- 2,905
6
votes
Did any computer systems connect "terminals" using "broadcast"-style RF to multiplex video, and some other means of multiplexing keyboards?
Well, if custom build devices also count, I would present the SLS-Guckies :))
It was a quite unusual terminal system custom build based on telephone keyboards and TV sets, build for a none existing in ...
- 208k
Only top scored, non community-wiki answers of a minimum length are eligible