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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
37 votes
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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
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28 votes
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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
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24 votes
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When did the PC bus start slowing access to video RAM?

This question starts with a number of misconceptions about early video, memory and bus systems that need to be addressed in order to clarify what this question really appears to be about. If you want ...
cjs's user avatar
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17 votes

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

The Atari VCS (it only became the Atari 2600, when the 5200 became a thing) is somewhat peculiar, as its video and audio chip, the "Television Interface Adapter", better known as TIA, ...
masswerk's user avatar
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16 votes

How does Quake 1 access video memory in software mode?

When running in software mode, Quake uses SciTech's MGL. The screen buffer is locked using VID_LockBuffer which calls MGL_beginDirectAccess: void VID_LockBuffer (void) { ... ...
aybe's user avatar
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15 votes

When did the PC bus start slowing access to video RAM?

TL;DR: When the CPU-bus became faster than the I/O-bus Now, there are always going to be wait states during active scan line, because the video chip is using some of the video memory bandwidth for ...
Raffzahn's user avatar
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14 votes
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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 ...
Justme's user avatar
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14 votes
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Why was the SNES color gamut RGB?

The SNES has 256 color palette with 15-bit RGB entries. It makes sense as the video chip can in hardware blend colors from different layer in RGB colorspace, something which isn't as easy in YUV, and ...
Justme's user avatar
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13 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 ...
tofro's user avatar
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12 votes
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How much extra did a color RF modulator cost?

An RF modulator is an RF modulator. It just modulates whatever signal you feed to it. There should be no difference between RF modulators that either can or cannot do colour, as it does not care if ...
Justme's user avatar
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12 votes
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NTSC scan lines used by 8-bit computers

I found one document which might shed some light why 192 lines was used before 200 caught on. The TI 99/4 used a TI TMS9918 VDP, which based on the document, was designed as a chip for simple low cost ...
Justme's user avatar
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11 votes

When did the PC bus start slowing access to video RAM?

The original CGA always imposed wait states on display memory accesses. The card's memory subsystem always performs one access every four pixel clocks, and only half of those are available to the CPU ...
supercat's user avatar
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10 votes

NTSC scan lines used by 8-bit computers

Conjecture #1: NTSC title-safe area (unlikely) An NTSC video frame has 525 lines. After subtracting the 21 lines of vertical blanking, and the 20% of the visible area that was considered non-title-...
dan04's user avatar
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10 votes

NTSC scan lines used by 8-bit computers

Similar to the TI VDP answer, have a look at the Apple text mode layout described in this answer. (And keep in mind that the graphics video layout is based on the text layout). There are 40 characters ...
dirkt's user avatar
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10 votes

NTSC scan lines used by 8-bit computers

Older television sets used round picture tubes with a bezel to mask off the edges of the scanned area. Picture tubes were often circular, and to maximize useful areas, the image was expanded to the ...
supercat's user avatar
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9 votes

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

It seems you think that there is a frame buffer for a full video screen. And that the CPU draws stuff into the frame buffer and some video chip reads out the frame buffer and sends out as video. But ...
Justme's user avatar
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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 ...
Sep Roland's user avatar
  • 1,185
8 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 ...
Peter Cordes's user avatar
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8 votes

Which computer first used stored characters (shape selector) and character bit patterns in the same memory

TL;DR: Cogar C4 of 1972 Not any computer you may have thought of, or was it? The Cogar C4, aka Singer/ICL 1501 was an all-in-one 8-bit system featuring a built-in 4/8 lines at 32 characters CRT based ...
Raffzahn's user avatar
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7 votes
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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 ...
Justme's user avatar
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7 votes

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

I would say that 1990s LCD displays did not use 60 Hz refresh. At least the one I had on my first laptop in 1997 was a passive matrix display, with 30 Hz refresh rate and very slow response time. Not ...
jpa's user avatar
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6 votes

How much extra did a color RF modulator cost?

A bit of googling finds this for the Apple II: Dealers would sell an Apple II with a “Sup’R’Mod” (costing about $30) if the buyer wanted to see the graphics on their color TV. Also, I don't think ...
dirkt's user avatar
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6 votes
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Were jailbars inevitable from VIC-II analog output?

Of course it is only one opinion how it should have been done. There's also infinitely many other ways how it could have been done. It is true that all the signals affect the video output, maybe ...
Justme's user avatar
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5 votes
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How do I wait for end-of-frame (VSYNC) on a TRS-80 models 1 and 3?

There's no way to do it on the Model 1. The Model 3 has an interrupt that triggers every second vsync. Bit 2 of I/O port $E0 set to 0 indicates when the interrupt is active and can be enabled by ...
George Phillips's user avatar
5 votes

When did the PC bus start slowing access to video RAM?

Actually, if you carefully read the BIOS for the IBM PC and CGA video (I did), you will find that (at least in text mode) it delayed every access to the video memory until the display entered a ...
David G.'s user avatar
  • 151
5 votes

Were VGA palette's HSV math properties used in practice?

I don't think it's the same palette, but XCom/UFO used a palette composed of the same colors at different brightnesses so that it could do dynamic lighting with it. I think this may have been a ...
davolfman's user avatar
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5 votes

Were jailbars inevitable from VIC-II analog output?

I've not studied the internal layout of the VIC-II chip in detail, but I strongly suspect that power and/or ground has to go through some rather thin strips of metal (or worse, silicon) en route to ...
supercat's user avatar
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4 votes

Detecting if a video mode is supported by INT 0x10

There's a big list of video modes available, but how can I be sure that the video mode I want to set is supported? There is no easy way - unless you can determinate what kind of Card it is. For new ...
Raffzahn's user avatar
  • 226k
3 votes

Were VGA palette's HSV math properties used in practice?

I would believe the question is not really answerable the way it is. For one,the default palette is a manufacturer side offering, as such intended for low effort application, the ones that do not take ...
Raffzahn's user avatar
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