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71

DOOM itself doesn’t do anything special to benefit from PCI graphics cards. It runs faster with PCI graphics cards (and VLB, AGP, and PCI Express cards) than with ISA graphics cards because the supporting bus is faster, so reads from and writes to video memory take less time. PCI goes to great lengths to preserve backwards compatibility with ISA-based VGA, ...


47

The manual says that the smallest resolution it can handle is 800x600. That is almost certainly the key. Original VGA supported 640x480 16-colors and 720x400 (essentially a small step up from the 720x350 monochrome (MDA) text, but with color). While VGA has come to mean "any video card and monitor that uses a blue 15-pin connector" that's not what ...


31

Seems like VGA only has one background layer, it appears to be a typical bitmap screen like most home computers of the 80s (Amstrad CPC, Commodore 64 etc.) where each pixel's color is stored in a section of memory that can be written to directly. Most video cards of the day could theoretically have up to four pages of video memory, as they had 256 KiB of ...


30

(When selecting an answer, use Stephen's - I just put this here because it is too much text for a comment) Most Important: It's a Game of Raw Numbers. We can ignore more complicated stuff and simply go for bandwidth: ISA had at the time a bandwidth around 16 MiB/s (*2) VLB (*1) and PCI offered up to 133 MiB/s bandwidth. A 320 x 200 screen needs 64 kB (...


29

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 ...


29

VGA was introduced in 1987 with IBM's PS/2 line. NEC and VESA developed SuperVGA in 1988, but at the time it used the old and slow 8/16-bit ISA bus. Improving video performance was a top priority at NEC to help sell its high-end displays as well as its own PC systems. By 1991, video performance had become a real bottleneck in most PC systems. (316) ...


22

DOS is almost surely not outputting 800x600 or up, and is probably in the ballpark of 720x350 or thereabouts. Further, it's likely 70Hz, which this adapter may not like. I'd recommend you get a display that can use the signal from card natively -- any old multiscan CRT and lots of early LCDs can do this -- but if you're determined to use this adapter, you ...


21

In the UK in the 1980s and the early 1990s, no video input at all was common. Early video recorders and set top boxes (for the new digital channels) would use RF out. You would disconnect the aerial from the TV, connect it to the VCR or STB, and connect the VCR or STB to the TV with another aerial cable. The TV would see it as an extra channel. You might ...


21

The 64 has separate outputs on the video port for luma and chroma which you can adapt to an S-Video output. There are a few caveats, however. The chroma signal is a bit "hot" compared to the S-Video standard. The S-Video spec for the chroma line for NTSC is 626.70mVP-P (75% Color Bars), 835.60mVP-P (100% Color Bars) and for PAL 663.80mVP-P (75% Color Bars)...


20

Up until ~1980 the only connectors TV sets had were Belling-Lee type antenna in. So most VCR and next to all home computers did use RF modulated output toward the TV set (*1). This included even cable networks. While Type F connectors where used for more sophisticated equipment, households were still fitted with Belling-Lee. Professional equipment of the ...


20

All VGAs support the “official” CGA and EGA modes, so most CGA and EGA games work fine. However, compatibility can only be relied upon at the BIOS level; a VGA can be implemented without strict hardware compatibility with the older standards. This affects some CGA games in particular. There is a CGA test tool available. It was written following this ...


19

S-Video relies on colour transformation from RGB to YUV, and then takes the U and V and modulates them using a colour subcarrier. The TV has to undo all these steps in order to get the original RGB signal. If the subcarrier frequency is not in phase with the pixel clock (as will be the case if using different crystals), then moving artifacts will show up in ...


17

Some laptops have built-in support for inverting the screen in one form or another; Toshiba laptops for instance have a setup menu to configure gray-scale translation and inversion, as well as a pop-up TSR and a command-line tool (VCHAD on VGA systems). If your system doesn’t have anything like this, I think your options are rather limited... As mentioned ...


16

Before SCART, European TVs often had not video input at all or S-Video on 6-pin or 8-pin DIN sockets (not Mini-DIN). Cinch composite was uncommon until VCRs came out. After that the old S-Video connectors died out and it was most common for cheap TV sets to have only an antenna and one composite in, better TV sets had a SCART input very early. Component ...


16

I think that this was part of the larger trend of IBM losing the leadership of the “PC”, especially after the PS/2 and the MCA debacle (although the PS/2 line did introduce many new features which became de facto PC standards). Looking at graphics specifically, after the VGA, IBM developed the 8514/A and then the XGA. For most consumers these had several ...


15

[I]s there ever a circumstance where Mode 13h is a better choice for fast scrolling DOS games over Mode X? Sure, to start with, any single pixel operation on in Mode X is slower than for Mode 13, as the desired plane needs to be set first (*1) Next, the latch-trick (*2) can only move horizontal by 4 pixels at once. So any horizontal scroller will be ...


15

Many PC pinball games use Mode X, notably Pinball Fantasies, Pinball Illusions and Epic Pinball. Nerdly Pleasures also has a comprehensive post on games using “unofficial” resolutions, which includes a number of other games which support 320×240: Quake, Earthworm Jim, The Lost Vikings, Norse by Norse West, and Scorched Earth. On Moby Games, such games are ...


15

What was the phosphor resolution? The usual specification quoted for CRT resolution is the 'dot pitch', or distance between groups of RGB phosphor dots. Here are some examples of IBM monitors produced from 1987 to 1993 (taken from here):- Model Year Standard size viewable pixels dot pitch (mm) notes 8513 1987 VGA 12" 10.4" 640x480 ...


14

Preface: The question sounds as if you're missing a basic understanding of interfacing and communication between different chips/systems. At the core it can't be answered without a whole course in digital electronics 101. So I can only try to give some hints to understand the various concepts presented. I've come across a couple of projects that manage to ...


14

Running your code as-is on a real 286/VGA (Cirrus Logic CL-GD5420) produces this image: Inserting one dummy read before the second fill cycle (just mov ax, es:[0]) gives the image you were expecting: So it would seem that at least there might be a difference between the DOSBox implementation and the real hardware. If it does implement logic operations, ...


12

A direct connection is not going to work - The Gameboy's pixel clock is much too low to drive a VGA screen: GameBoy VGA Pixel clock 4 MHz 25 MHz V-Sync 60 Hz 70 Hz H-Sync 9 kHz 31 kHz So, in a nutshell, this will not work without a significant investment into capturing the GBA ...


12

It cost me something like $50 all up to connect my Electron to the TV using an RGB to SCART cable (this one from eBay) and an RGB to HDMI converter like the one pictured below: You can get this model from a bunch of different eBay sellers, under various different brand names, but they're all the same. I've tested it out with MODE 0 - MODE 6, and it seems ...


12

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 ...


11

The Electron outputs an analogue interlaced 625-line image, with a line rate of 15.625Khz. HDMI is a digital input, so cannot comprehend the Electron's analogue output. VGA is analogue but many monitors expect a line rate of 31 kHz. It's not impossible that your screen would be okay with 15.625Khz though, as that's the PAL standard, so you could at least ...


10

In analog TV, there was such thing as interlace. Roughly speaking, it kind of increased vertical resolution by putting scanlines of one "halfframe" (the one that lasts 20ms or goes 50 times per second, or, alternatively, 16.6ms and 60 Hz) between the scanlines of previous halfframe (saying scanlines I mean lines lit by electron beam on CRT). As the ...


10

Is it on its own plane somehow? No, as you assumed, VGA has only one plane(*1). Is every letter a "mouse cursor?" Or, is the screen constantly being redrawn with the letters in their new position? The latter. Most likely it's composed of a background image moved into the frame buffer, overlaid by the text layer. (*2) The movement of the text is ...


10

The 16-color modes on the VGA use a hardware design borrowed from the EGA. On the EGA (and VGA), the bitwise drawing modes don't act upon memory directly, but instead act upon values stored in four eight-bit registers, each of which holds a byte of data from one of four color planes. Reading any byte of data from the display will load each of the four ...


9

Black-and-white hi-res from the 1040 STE on a VGA monitor should work with a direct connection and no tricky electronics at all (just the adapter cable) Atari VGA GND 13----X---- GND ---------4 GND Sense 4----+ +--------------2 green ...


9

The other answers are good, but one specific area where VGA cards are generally incompatible with CGA is with respect to CGA's Composite mode. In the video "CGA Graphics - Not as bad as you thought!", The 8-Bit Guy demonstrates the CGA Composite mode and explains that, after about 1987 or so, new software written specifically for CGA Composite Mode became ...


9

Your problem is mostly going to be rep movsb changing that to use rep movsw should help. If the VGA card is on a 8MHz (or 6MHz) original AT bus then the timings work like this: 3 cycles to read or write a byte 19,200 bytes being moved. 345,600 bus cycles per copy 8,000,000 / 345,600 is 23.14 copies per second. 6,000,000 / 345,600 is 17.36 copies per second. ...


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