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54

A nice one - and coming up every now or then. TL;DR The Apple IIs video logic produces a B&W bitstream at the right frequency to bedazzle an NTSC TV set in a way to make it 'see' colour. The colours produced are based on the way the bitstream creates interferences that are detected by the TV set as colour information. The encoding is rather a series of ...


51

They were different. You probably already know that NTSC is 60 Hz and PAL is 50 Hz. The video generation hardware was much more 'bare metal' than today (the NES color palette implementation was so bare metal that one of the colors you could select, referred to as 'blacker than black', could mess up some TVs due to the way the NES simply fed the color bits ...


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 ...


28

The NES's region lock is implemented in hardware, not software, with the CIC chip. The NES contains a CIC, and each authentic cartridge contains an identical CIC. When the console is powered on, the two chips communicate via a challenge-response handshake protocol, and if the cartridge fails to provide the correct responses, the CIC on the NES resets the ...


22

TL;DR Any (*1) colour can be displayed. The signal is analogue and can be very fine tuned. But tuning needs time, thus not every colour can be shown beside each other (without a transition thru others). The Long Read: NTSC, like PAL or any other colour encoding can produce any colour, well, within its 'spec' that is. Colour encoding is based on a relative ...


20

I think you're conflating a few issues: being in-phase with the colour subcarrier; being sampled at a rate less than or equal to the colour subcarrier; and being sampled at an integer division of the colour subcarrier. Being in-phase has exactly one effect: the artefacts on horizontal edges are consistent from one line to the next. The edges do not ...


17

The PAL video encoder was not a bottleneck of any kind. It is left out because the unit is not a PAL model, but a SECAM model, which needs a different kind of encoder. So the chip is not needed and it would be useless and just cause extra cost and power consumption in the SECAM model. The necessary SECAM encoder is integrated to the separate board with the ...


16

Basically the difference between PAL and NTSC consoles is the frame rate, 50 vs 60 Hz. The consequence of that is that PAL and NTSC mostly differ in number of cycles available for the CPU per frame, with NTSC numbers being significantly smaller. More subtle differences might be number of cycles per scanline, position of visible screen area related to the ...


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 ...


13

The pixel clock has to be fast enough to generate the number of pixels you want to display horizontally within the 56 microsecond scan line interval. At 3.58MHz, you only get about 200 pixels. This was fine for the Atari 2600 et al, which had 160 horizontal pixels, but the other systems you mentioned had higher horizontal resolution, so had to use a faster ...


12

The pixel clock doesn't have to be the same as the color clock. In fact, it's usually higher. Remember that in a composite video signal, the chrominance information (whose resolution depends upon the color clock) is less important than the luminance information (whose resolution depends upon the pixel clock), so the color clock can be (and usually is) slower ...


12

I had two micros when I was growing up: the SAM Coupé and the Acorn Electron. The SAM Coupé has a 512x192 mode much like you discuss. The SAM's display is physically wider than a Spectrum's though, pixels being approximately 1.25 times as wide as tall. The Acorn Electron inherits full 80-column 640x256 video from its progenitor, the BBC Micro. In both ...


11

A typical black and white television will be capable of displaying 80-column text that can be read, but such text will generally be sufficiently unpleasant to read that some other kind of display would be preferable. Among other things, a monitor which is adjusted to have extremely sharp focus and modulate the beam very sharply will generally produce a ...


11

Yes, but only a very slightly different speed: the master crystal was around 14.238Mhz rather than 14.31818Mhz. which is only around 0.5% different, so I would expect safely within tolerance for a Disk II. Something PAL users didn't get from the base machine: colour. The relationship with phase is a lot more complicated in PAL, as that's how the error ...


10

While nominally 241 scan lines were visible in the sense they contained video information, all TV sets hid a varying amount of scan lines on top and bottom (and left and right) by overscan and by the bezel in front of the screen. So with a vertical resolution of 240, on most TV sets parts at the top and bottom would not be seen. While this doesn't matter ...


10

Rather than convert the NES, just get a PAL monitor. The common auto backup video systems use an NTSC/PAL switchable monitor, available for not much money.Backup monitor 7" It is also possible, with some video capture cards, to select PAL (then your computer display will allow you to use the game). If your TV takes PAL input (some do: check all the ...


10

Technically, no, because usually hardware was fixed to generate the TV signal in a fixed way, instead of being programmable. Many systems had separate video chips for different TV systems, and due to the difference in the video timing or color encoding, also the clocks available in the system to run the CPU or audio chips varied. So basically, taken a NES as ...


9

Short Answer: There is no relation. What seems like a relaiton is non related coincidence. Long Answer: First of all, there is no colour clock. The mentioned frequency of 3.58 MHz is not a colour clock, but the carrier frequency used to modulate the encoded colour signal atop the basic B&W signal. There is no relation to RAM speed, pixel generation or ...


9

It depends on whether the TV is color or black-and-white/monochrome. Older B&W TVs (and ordinary TV electronics and tubes converted into monochrome monitors by some el-cheapo monitor vendors), did not block (filter out) color burst frequencies (with the associated IQ bandwidth), and the cheap analog filtering did gracefully degrade as the bandwidth was ...


9

You'll have to get a PAL to NTSC converter. A modification to make a PAL NES to output NTSC video would be extremely difficult because both the console and the games are designed for the video signal. The NES's clock frequencies were chosen to match the timing of the video signal, so you'd have to replace the clock circuitry. The PPU is hard-wired to ...


9

TLDR: It's a soft spot for optimization around the ability to display 25 lines of text. (And why this is important has been discussed some time ago in an answer to your question about why 80x25 became standard) Preface: As usual with such decisions there are many factors involved - and most of them are not hard but variable within a certain frame and in ...


8

At startup, the Amiga used a timing routine to check the frequency of the AC power supply, and start in PAL (50 Hz AC) or NTSC (60 Hz AC) appropriately. Unfortunately, the detection was buggy, and sometimes 50 Hz was wrongly identified as 60. Many Europeans would have Declan McArdle's NoPALReset in their s:startup-sequence to avoid this. I think the problem ...


8

NTSC provides 227.5 colour cycles per line; PAL is very close to 283.75. In both cases, the visible area is around 80% of the line, but most home computers had a much bigger border than that — e.g. (of those I know offhand) the Acorn machines paint for 40µs, which is 62.5% of the line; the 48kb Spectrum paints for 128/224ths, which is around 57%; over in ...


8

Not sure if you should call it an advantage, but the Apple II used the double color clock frequency to create colors. Consider two bit patterns, 0101010101 1010101010 On a monochrome display, they represent just a dotted pattern. On a color display, you have a signal with the frequency of the color clock, but with a different phase. And the phases produce ...


7

The V9938 video chip in the MSX2 home computer can be programmed to disable the color burst but I don't know if any utilities or applications provided such an option to the user. That would have certainly been beneficial for the 80 column text mode and 2-color high resolution bitmap mode. Some MSX2 variants had a V9958 instead which has no composite video ...


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

I've never used one of these devices, but I can see from the photo that the device has the typical inputs you'd find on studio equipment at the time, and for many years after. It appears to accept NTSC composite video, TTL RGB, and Analog RGB with a composite sync, or RGBS (using EXT. SYNC input). NTSC composite input would work with consumer VCR's and ...


6

If I were designing video hardware and wasn't wanting to exploit chroma aliasing, I'd probably use a dot rate of about 10/3 or maybe 3.5x chroma, which would yield pixels with a roughly 1:1 aspect ratio in interlaced modes, or 2:1 in non-interlaced modes. If it wasn't necessary to go out to the border, that would yield a nice power-of-two screen size (512 ...


6

No, not quite like that. Nobody pointed out to you that the pixel bits are stored in reverse order. 0 00 01 10 1 -> 0 1 01 10 00 = 58 1 1 00 01 10 -> 1 01 10 00 1 = B1 How can you see what it looks like? You could do it like this: HGR CALL-151 2000:58 B1 N 2002<2000.3FF6M But then you'd see it doesn't look like what you expect, so I wrote you a ...


6

The Apple II Reference Manual (Apple product number A2L0001A), published in 1979 by Apple Computer, Inc. for the Apple II and Apple II Plus computers, contains a few pages about the end-user data format of the high resolution graphics mode: Each dot on the screen represents one bit from the picture buffer [a dedicated 8K region of memory]. Seven of the ...


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