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85

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, 80x25 text mode. The original VGA 80 x 25 text mode (that is still supported by most modern graphics cards) has characters with a resolution of 9x16 pixels per character. This adds up to 80 ...


68

There were a few reasons: Old monitors had very low refresh rates (driven by hardware prices), and green phosphor has the longest afterglow (remains on the screen for the longest time) Green phosphor was the first available for use in monitors (and some sources also say that monitors of this type were physically lighter) It was the brightest type of ...


61

Having the display vertical reduces the width of the cabinet. This means that a game machine can be fitted into a smaller space in a pub/bar, or in an amusement arcade where machines are in rows you can get more machines (potentially a third more) into the same space. One-third more machines means one-third more revenue. The orientation may also have been ...


37

As comments on the question already suggest, it looks quite like an address fault when video memory is read. While the picture is not really great, I'd say: Blocks of 8 lines are visible, so it must be about A9 of the video address generator (*1). Since these 8 lines are displayed twice, A9 must be tied to one level. From the content it seems as if the '...


35

CRTs don't have pixels, they don't work that way. Also, arcade monitors expose all the picture controls at the back so it is possible to adjust them quite extensively. Operators would have made sure that the picture was the right shape and in focus near the edges. Since the controls are all analogue and no-one bothered to measure the display geometry the ...


35

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 signal to the monitor was to prevent crosstalk interference of these signals. You can see this in the very early computers like the Commodore 64 and Atari 800 ...


31

CRT TVs are analog devices, there is no "pixel", but the size of the spot limits the resolution of the image, as the size of silver nitrate crystals limits the resolution of photo films. Several arrangements of the colour stripes on the CRT tubes have been designed, they are a compromise between resolution, luminosity and the precise alignment of the ...


30

Why did the original Apple //e have two sets of inverse uppercase characters? Simple: To allow lower case inverse letters. It's all about the clever way Woz arranged the original II's single character set to save in hardware and offer additional functionality. There is only a single character set of 64 characters, showing up 4 times in 256 entry character ...


28

VGA's 640x480 mode was the first to offer square pixels and an exception among all VGA modes available (320x200, 640x200, 640x350 and 720x400 for Text). Square pixels weren't the standard back then. Adding video modes in later (Super) VGA was kind of a marketing game to offer higher numbers to outpace competition. First it was Colour, like offering 640x480 ...


27

ZX Spectrum: has 21 user definable graphics (UDG) available to the user via POKE USR command. Also, main character set can be redirected to RAM (sysvar CHARS, 23606-23607) so it is fully definibled. It doesn't have a real text mode. All text is rendered into pixels by the firmware. Jupiter ACE: has the entire character set in dedicated RAM (but available in ...


24

EHB For example, a game that uses EHB (Extra HalfBrite) mode during the game action (i. e. ingame) is Pinball Dreams. In my example run of the Beat Box table I can find the following in the copper list: $00D6EA WAIT $4211FFFE $00D6EE MOVE #$6200,BPLCON0 I. e. it waits for raster line $42 (66) and uses BPLCON0 to set the number of bitplanes to 6 without ...


23

Actually, the screen stripes while loading from tape first occurred on the ZX-81 - Where they were a result of Sinclair's typical savvy nature - the display and the "EAR IN/MIC OUT" had to share a pin on the ULA and thus made the (whole) screen flicker in stripes during tape loading and saving. This actually proved useful as a visual clue the computer still ...


23

Before VGA was invented, CGA RGBI used 4 wires to get 16 colors and EGA used 6 wires to get 64 colors on the cable. Add 3 more for sync signals and signal ground, and this won't be an issue, simple cables and connectors exist for getting EGA's about 16.3 million pixels per second digital signals over to the monitor easily. Amiga was released. It supports 4 ...


22

The cheapest option is to use the composite output, so it's compatible with any monitor that supports composite but it's only black and white. Or if you have the A520 modulator (about $25 on eBay), you can get a color image through composite, RF (not recommended), or modify the A520 for S-Video. If your TV has a standard definition tuner, you may also be ...


21

Addressing the "why" part of the question - from my point of view as an assembly-code programmer on PDP-11 and VAX, the "standard" radix is most usefully chosen to match the instruction layout. PDP-11 had 8 registers and 8 operand-mode indicators. Its double-operand instruction layout was 1 bit generally byte/word indicator (b) 3 bits opcode (o) 3 bits ...


20

Yes, it is possible. There are a number of ways: If your TV has a SCART connector, you need a cable adapter from DIN 6 to SCART, wired like this (the audio is taken from the audio out using a standard stereo 3.5'' jack): (taken from CPCwiki) If your TV does not have SCART, but composite video input, you must Either use a RGB to CVBS adapter (using for ...


20

Digital Research produced as one of their early attempts into graphical desktops (on their way to GEM) a basic portable graphics library - GSX. GSX did actually support proportional fonts, both in print and on-screen, and was included with the CP/M support in Amstrad machines running CP/M Plus. GSX was supported by two of DR's own applications, DR Draw and ...


20

(From the perspective of the electronics, that means the displays were drawn sideways.) Not necessary. There is no inherent reason for drawing sideways. A video circuit can easy be made for either, as line width and number of lines can be defined either way. This is especially true for early games, where electronics were rather special to type and so was ...


19

Was CP/M ever used, in practice rather than just as a tech demo, in less than 80 columns? Most prominent here may be the Apple II with Micro- Soft's Softcard. While most users did use it with an additional 80 column card, it also worked well using the basic 40 character display. After all, CP/M itself wasn't tied to any display size or a CRT at all. ...


19

Canonically in NTSC standards the drawn lines are tilted slightly so that the start of the odd field starting at the left is perfectly level with the top of the even field starting in the middle horizontally. The actual angle though is so tiny, ~0.09 degrees, that it's negligible compared to the rotation error you'd get just from the earth's magnetic field ...


19

TL;DR If you don't want to rely on an intermediate device, such as a "scan-doubler", then you need a screen that includes analog inputs and internal electronics capable of displaying a low-definition 240p video signal. The real issue is the inability of those screens that do have the composite video input to correctly deal with a signal source that ...


18

The 8080 is not a microcontroller, but a microprocessor, so it had no special provision for LCD displays, as modern microcontroller may have, except maybe for the ability to use packed BCD numbers. It had no in-built host peripherals that would support protocols like RS232 or SPI. You don't mention what kind of LCD display your college used, so this is only ...


18

The Commodore Amiga (all models) had hardware support for overscan on CRTs. This was accessible to the user through the Preferences settings, as shown in the dialog panel below. The Preferences setting allows for quite a bit more screen real estate on the Workbench screen, and is quite useful for productivity apps. For games, software control of overscan ...


18

Modern smart TVs may have analog inputs, but they are very "picky". They often do not work with older computers. My two Smart TVs cannot display even Amiga nor Atari ST, although they provide Composite input, RGB SCART, etc. So I have one very old TV for all my retro machines. The problem is nobody can say if your TV will work with your C64 before ...


15

The TI-99/4a has a CALL CHAR command to redefine one ASCII character at a time. The first argument is the ASCII code and the second is the 8x8 map expressed as a series of hex digits. (This is how I learned hexadecimal back in elementary school. Good times!)


15

Well Cromenco have something on page 2 of this issue of byte. https://archive.org/stream/byte-magazine-1980-11/1980_11_BYTE_05-11_High-Resolution_Graphics#page/n1/mode/2up 756x482 in 16 colors, and on page 70ish there's an article which talks about max raster screen resolutions of 1024x1024. Also worth looking at is the HP9845C with a cost of $39,500 ...


15

IIRC, the electron gun was actually installed in a position where it was rotated slightly relative to the tube, to compensate for this effect, so the scan lines did end up being horizontal.


15

The when and why of use of hexadecimal over octal representation is intimately tied in with where and what: the use of one over the other depended greatly on environmental factors, as well as the machine itself, with programmer preference mainly being developed by the influence of these. As Raffzahan points out, IBM 360 environments used hexadecimal from ...


15

Amstrad used an off-the-shelf component, and did the best they could. For generating video addresses, sync timing, etc, Amstrad used the 6845 CRTC, which was originally designed for text displays. In particular it is designed for a linear text area, looking up character graphics from a font ROM, so e.g. if you’ve set up a 40-column display with 8px ...


14

No, they're purely for communication with the user. Coloured stripes = loading, slow colour changes = not loading. Setting the border colour on the Spectrum is achieved with a simple port output. The stripes are an elementary raster effect — all that's happening is that the tape loading routine is changing the border lots of times within a frame. If you ...


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