Hot answers tagged

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 ...


34

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 ...


25

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 ...


21

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 ...


19

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 ...


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 ...


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 ...


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.


14

Did arcade monitors have same pixel aspect ratio as TV sets? Short answer: No, not necessarily. Long Answer: To start with, 'Title Safe Area' is an idea to define the parts of one transmission to be displayed even if any of the many receivers is maladjusted. It's nothing inherent to the TV signal or its definition, it's a safeguard against less than ...


14

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 ...


13

There are a number of tools you can use to tweak the display mode, including setting it to 640×480. The Free Software for DOS site lists a few, of which I’ve successfully used VBEHz and Text Mode in the past. SVGATextMode, as mentioned by Radovan Garabik, would also allow you to configure your display in great detail. The 720×400 mode you’re seeing is ...


13

Prior to DEC's PDP-1, of 1959, there would be MIT's TX-2 of 1958 - after all, the PDP-1 (and DEC itself), was a spin off of this project (and team). That said, it was only a single machine and a research project, not anything commercial available. Before that, there was the SAGE system, operational in 1958, which was used for RADAR surveillance. Images from ...


12

Yes there are a lot of compensations in a CRT like: magnets counteracting background magnetic fields circuits counteracting curvature of CRT screen surface circuits counteracting different length of the beam (edges/center) "linearizations" of brightness (gamma correction) and probably much more I can not think of right now... But back to your question the ...


11

Older monitors had analog timing and, with one notable exception, were designed so that the signals presented on their inputs at any moment would fully describe the color to be displayed at that moment. The only monitors that used any sort of time multiplexing on their inputs were those that used the same analog composite color encoding methods used in ...


10

TL;DR; Did any computer allow overscan on a non-TV monitor? Every computer that allowed overscan did the same on TV and non-TV. Computer-to-TV transmission only differs from computer-to-CRT by having the frame signal modulated onto a carrier during transmission. Modulation doesn't change any part of the payload (*1) regarding timing, which, relevant for ...


9

When and why That is quite close tied to the IBM /360 and its introduction in 1964. The /360 is based on the use of an 8 bit byte, 32 bit word (16 bit half word) and 24 bit address. Thus all basic memory items were multiples of 8 bit units - which are, without any remainder, best be displayed in hex. In addition displaying bytes in hex correlates well with ...


8

Minicomputers and mainframes typically used octal, as many early mainframes had word sizes that were a multiple of 3 bits, and so did some minis. Operators and engineers within those environments became used to this, so even power-of-two word size minicomputers kept using octal. Microcomputers, however, almost always had power-of-two word sizes for both ...


8

That question is built on somewhat weak ground. After all, most of the video formats you list as 'digital' aren't such - or at least not more as any of the analogue ones are. Just because an output like RGBI uses two levels per channel doesn't make it digital. They only feature a restricted number of signal levels. Digital signalling only started with ...


8

There is a Linux utility called SVGATextMode which can switch the resolution in text mode; there is also an MS DOS port, but you probably have to hunt for the binaries yourself. EDIT: found the binaries (no guarantee!): https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/util/user/svgatextmode/svgatextmode_1_9_16rc1-dos.tgz Read DOSPROGS.TXT inside ...


8

The first release of Windows to provide built-in support for multiple monitors, on graphics cards with appropriate drivers, was Windows 98. Support was subsequently added to the NT line with Windows 2000. Some graphics cards provided support for multiple monitors in earlier versions of Windows, at least in Windows NT 4.0 as described here (with SP3, ...


8

According to EBU R95, the title-safe area for 576i format (corresponding to PAL SDTV) is 258 lines tall in each field. This is just large enough to accommodate the 256 lines per field that the BBC Micro uses. This is probably not a coincidence, as the BBC Micro was in part designed so that the BBC itself could use the micro for generating titles and ...


7

Asteroids is an example of an arcade cabinet that didn’t even use raster graphics, but vector graphics. Battlezone and Lunar Lander were others. They used similar technology to the Tektronix 4000-series terminals of the ’70s, or the IBM 2250: A cathode ray fired into the back of a glass screen coated with phosphors, like in an old-fashioned black-and-...


7

Quoting Wikipedia, it seems to be at least two factors: The availability of inexpensive LCD monitors has made the 5:4 aspect ratio resolution of 1280 × 1024 more popular for desktop usage during the first decade of the 21st century. (from here) The 1280 × 1024 resolution became popular because at 24 bit/px color depth it fit well into 4 megabytes of ...


7

1280x1024@24-bit fits in 4 MiB. Why wouldn't you take extra screen space? Keep in mind that games didn't usually run in 1280x1024 at the time. Back before LCDs became the dominating screen technology, you didn't care about the "native resolution" of the display - you didn't get the ugly "one pixel is stretched over two physical pixels, its neighbour only ...


5

from digital to analog, then back to digital? Simple answer: It didn't go "back" to digital. Why? Although the EGA and the HDMI signal are both "digital" and the VGA signal is "analogue", the (digital) EGA signal is quite similar to the (analogue) VGA signal but it is completely different from the (digital) HDMI signal: Both in a VGA and in an EGA ...


5

To expand further, it actually wasn't especially feasible — there is no easy solution that doesn't eliminate the interlacing. Interlacing works because the timing of the vertical retrace varies. On odd fields it is triggered so that scanning resumes at the beginning of a line. On even fields it is triggered so that scanning resumes in the middle. Because of ...


4

The effect you are describing did not matter, mainly because in a television the effect is so small, and the TV camera also had a CRT tube that converts light to video signal in a matching scanning pattern so the picture is in fact not tilted due to the scanning. Computer systems usually used progressive scanning on CRT monitors so for example VGA has twice ...


4

The Amstrad CPC machines came with a CRT monitor. Some games included use of the overscan area (border). For example, Arkanoid drew into the top and bottom borders to create a taller play area.


4

RF encoding introduces significant noise to the video signal because it moves the signal up to an area of the spectrum that is much more susceptible to interference. A monochrome 240p video signal of the best quality will be defined by its dot clock frequency at ~14 MHz. This would create a good quality 80 column text image as seen on machines like IBM CGA ...


3

In the video you linked (at 01:12), I notice that this device has the standard yellow and white connectors for composite video and audio. Many cheap portable LCD TVs support this kind of input, and are often battery powered, too.


Only top voted, non community-wiki answers of a minimum length are eligible