List of home computers by video hardware

This is a list of home computers, sorted alphanumerically, which lists all relevant details of their video hardware.
A home computer was the description of the second generation of desktop computers, entering the market in 1977 and becoming common during the 1980s. A decade later they were generally replaced by IBM PC compatible "PCs", although in actuality home computers are also members of the class known as personal computers.
Examples of typical early home computers are the TRS-80, Atari 400/800, BBC Micro, the ZX Spectrum, the MSX 1, the Amstrad CPC 464 and the Commodore 64. Examples of typical late home computers are MSX 2 systems, and the Amiga and Atari ST systems.
Note: in cases of manufacturers who have made both home and personal computers, only machines fitting into the "home" computer category are listed. Systems in the personal computer category, except for Early Macintosh personal computers, are generally all based on the VGA standard, and use a video chip known as a Graphics processing unit. Although very early PCs used one of the much simpler (even compared to most home computer video hardware) video display controller cards, using standards such as the MDA, Hercules Graphics Card, CGA and EGA standard). Only after the introduction of the VGA standard could PCs really compete with the home computers of the same era, such as the Amiga and Atari ST, or even with the MSX-2. Also not listed are systems that are typically only gaming systems, like the Atari 2600 and the Bally Astrocade, even though these systems could sometimes be upgraded to resemble a home computer.
The importance of having capable video hardware.
Early home computers all had quite similar hardware, (and software) mostly using the 6502, the Z80, or in a few cases the 6809 microprocessor. They could have only as little as 1 KB of RAM or as much as 128K, and software wise, they could use a small 4K BASIC interpreter, or an extended 12K or more BASIC. So the basic systems were quite similar, except for one part of the system, the video display hardware. Some systems proved to be much more successful than others, and careful observers will see that the most successful systems had the most capable video hardware. The reason for that is that the success of the home computer was mostly determined by the kind of games you could play on it.
If you wanted to run a nice video game on a home computer, all the other specifications of the system, such as the CPU, the kind of BASIC, even to a degree how much memory the system had (if it had 32K or more) did not matter much. What mattered most was what kind of picture could be put on the screen, and how easy or hard it was for a programmer to get enough capabilities out of the video hardware to create the effects necessary for the game.
A case in point is the Commodore 64. Its microprocessor lacked advanced math functions and was relatively slow. In addition, the built-in BASIC interpreter lacked any sort of graphics commands, as it was the same version that was developed for the older Commodore PET (a computer without any high resolution graphics capabilities at all). However, these drawbacks were of little consequence, because the C64 had the VIC-II chip. When accessed by machine language programs, the graphic capabilities of this chip made it practical to develop arcade-style games. Additionally, specific machine language coding exploiting quirks of the VIC-II chip allowed for special tricks to draw even better pictures out of the VIC-II chip. The comparatively large memory and the audio capabilities of the C64 also lent themselves well toward the production of desirable games.
A negative example was the Aquarius by Mattel which had such incredibly limited video hardware (for the time period) that it was retracted from the market after only four months due to bad sales.
Video arbitration logic.
One major problem that early computer video hardware had to overcome was the "video bus arbitration" problem. The problem was to give the video hardware (VDU) continuous read access to the video RAM, while at the same time the CPU also had to access the same RAM. The obvious solution, using interleaving time slots for the VDU and RAM was hard to implement because the logic circuits and video memory chips of the time did not have the switching speed they have now. For higher resolutions the logic and the memory chips were barely fast enough to support reading the display data, let alone for dedicating half the available time for the slow 8-bit CPU. That said, there was one system, the Apple II, that was one of the first to use a feature of the data-bus logic of the 6502 processor to implement a very early interleaving time slot mechanism to eliminate this problem. The BBC Microcomputer used 4 MHz RAM with a 2 MHz 6502 in order to interleave video accesses with CPU accesses.
Most other systems used a much simpler approach, and the TRS-80's video logic was so primitive that it simply did not have any bus arbitration at all. The CPU had access to the video memory at all times. Writing to the video RAM simply disabled the video display logic. The result was that the screen often displayed random horizontal black stripes on the screen when there was heavy access to the video RAM, like during a video game.
Most systems avoided the problem by having a status register that the CPU could read, and which showed when the CPU could safely write to the video memory. That was possible because a composite video signal blanks the video output signal during the "blanking periods" of the horizontal and especially the long vertical video sync pulses. So by simply waiting for the next blanking period the stripes could be avoided. This approach did have one disadvantage, it relied on the software not to write to the screen during the non-blanking periods. If the software ignored the status register the stripes would re-appear. Another approach, used by most other machines of the time, was to temporarily stop the CPU using the "WAIT/BUSRQ" (Z80) "WAIT" (6809) or "SYNC" (6502) control signal whenever the CPU tried to write to the screen during a non-blanking period. Yet another, more advanced, solution was to add a hardware FIFO so that the CPU could write to the FIFO instead of directly to the RAM chips, which were updated from the FIFO during a blanking interval by special logic circuitry. Some later systems started using special "two port" video memory, called VRAM, that had independent data output pins for the CPU interface and the video logic.
The main classes of video hardware.
There are two main categories of solutions for a home computer to generate a video signal:
Systems in the first category were the most flexible, and could offer a wide ranges of (sometimes unique) capabilities, but generally speaking the second category could offer a much more complex system for a comparable lower price.
The VDC based systems can be divided into four sub-categories:
Explanation of the terms used in the tables.
"A "-" in a table cell means that the answer is irrelevant, unknown or in another way has no meaning, for example the sprite size of a system that does not support hardware sprites."
"A "?" in a table cell means that the entry has not yet been determined. if a ? follows an entry it means that other options than the listed ones may also exist"
""Mono" in a table cell means monochrome that is for example black on white, or black on green."
The list of home computers, and their video capabilities.
Systems that fall into multiple classifications.
For these systems it is established that they are simultaneously based on multiple technologies. The hardware chosen to be used by these systems may have substantial or insubstantial impact on the video they output.
Systems that could not be classified.
For these systems it could not be established on what technology they are based. If you know more about the actual hardware used by these systems, then please move them to the correct class.