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23 votes
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Does every retrocomputer and console with NTSC composite output have 'artifact color' ability?

In composite video, a scanline has the following format: Every line has: a sync mark, which is the lower level, on the left. a color burst, which I'll explain below. video data. The sync mark is ...
Thomas's user avatar
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15 votes
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How do Z80 Block Transfer instructions work?

Unplug the soldering iron again. It's not really worth it. For one the Z80 operations are less flexible, but more important, they are also slower (clock by clock or cycle by cycle, as you prefer) than ...
Raffzahn's user avatar
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13 votes

Does every retrocomputer and console with NTSC composite output have 'artifact color' ability?

Colour in NTSC is represented as the high-frequency part of the signal. A colour-aware TV will separate the low and high frequency parts. The colour decided will depend on the relative phase of the ...
Tommy's user avatar
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12 votes
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How to connect a Tandy Color Computer to a Composite Monitor?

The TRS-80 Color Computer 1 and Color Computer 2 only supported RF output to a TV. It wasn't until the CoCo 3 that both composite and RGB output were added - RGB being essential for the new 80-column ...
Brian H's user avatar
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11 votes

Fate of mystery Motorola RMS graphics chipset (68486 + 68487)

Based on the absolute dearth of information on the Motorola 68486/68487 video chipset (RMS), I would conclude that it was never officially released as a product for OEMs, and was therefore never used ...
Brian H's user avatar
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11 votes

How do I change the CoCo 3 color palette before running a Color Computer ROM Pak?

If you have a Multi-Pak, put the Program Pak in Slot 1 and set the switch to slot 2. Turn on the Multi-Pak and then the Color Computer 3. type: PALETTE RGB to set the proper color set. type: POKE ...
tlindner's user avatar
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10 votes
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Could Tandy TRS-80 Color Computers boot from disk at all?

Thanks to RichF's answer I looked for information specifically on booting OS-9 and found that you definitely did have to manually launch even an alternative operating system. From OS-9 Level Two ...
hippietrail's user avatar
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10 votes

Which memory management is easiest to program - CoCo 3 or C128/Apple //e?

Neither CoCo nor Retro-Apples are my specific area of expertise - I'll try to answer from a more European viewpoint. Concepts and technical solutions are similar, however. Basically, all the ...
tofro's user avatar
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9 votes

Does every retrocomputer and console with NTSC composite output have 'artifact color' ability?

Let's sort out some different kind of color artifacts. 1) The composite signal carries both lumincance and chrominance, the latter encoded in the phase of the color carrier. That means if it's ...
dirkt's user avatar
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8 votes
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How do you implement double-buffering on a CoCo 3 320x192x16 screen in BASIC?

Page flipping is possible in high resolution graphics modes on the Color Computer 3 but there are a couple of caveats. First, the type of drawing and how much drawing your perform will certainly ...
Captain Obvlious's user avatar
8 votes

What's up with the ASxxx and the "CoCo Disk BASIC binary format"?

The original assembler released on the CUG volume 292 (see here for the files in that volume) had support for only the Intel Hex and Motorola S19 output formats. Support for the CoCo format was added ...
paxdiablo's user avatar
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6 votes

BASIC09 and I-Code

I can't speak to BASIC09 specifically, but there's quite a difference between an "i-code" and a tokenized form. At a minimum, the i-code, in the end, need not look at all like the source code, ...
Will Hartung's user avatar
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6 votes
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Fate of mystery Motorola RMS graphics chipset (68486 + 68487)

With some Google sorcery, I finally located a system that used the elusive RMS chip set: The Microbox 3 manufactured and sold by UK-based company "Micro Concepts" from Cheltenham! I can only find it ...
Fedor Alexander Steeman's user avatar
6 votes

Does every retrocomputer and console with NTSC composite output have 'artifact color' ability?

I think these are the necessary features: Color burst, or the ability to 'draw' before the left border Pixel rate higher than the colour clock, possibly a multiple and in phase No low pass filters on ...
Valentino Miazzo's user avatar
6 votes

How do Z80 Block Transfer instructions work?

Despite being believed as too slow, LDI- and LDIR-like commands in Z80 actually do their best in moving bytes. LDI takes 16 cycles in total, specifically 4+4 cycles to read the opcode, then 3+3 ...
lvd's user avatar
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6 votes

How do Z80 Block Transfer instructions work?

Yes, the Z-80 has block move instructions for memory, I/O and searching. These were additions made by Zilog and were more definitely not available on the Intel 8080. Nominally the Z-80 accesses ...
George Phillips's user avatar
5 votes

Could Tandy TRS-80 Color Computers boot from disk at all?

IIRC there was no need to boot the operating system. It was in the ROM as part of the machine's BASIC. There were actually two choices, with Extended Color Basic being in the more advanced machines. ...
RichF's user avatar
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5 votes
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Microware OS-9 assembler warning with no message

The Microware Assembler has no way to inform you of why it is issuing a warning. It keeps track of the total number of warnings, and also of the number of warnings on each line. If a line has any ...
Wayne Conrad's user avatar
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4 votes

Does every retrocomputer and console with NTSC composite output have 'artifact color' ability?

For NTSC artifacting to be most useful(*), the dot clock must be a multiple of chroma clock; on all such systems I know of where it's useful, it's either 2x or 4x. Further, for purposes of artifacting,...
supercat's user avatar
  • 37k
4 votes

How do Z80 Block Transfer instructions work?

IIRC, LDIR (et al.) is a 2-byte opcode. The repeat was implemented as a decrement of the PC rather than an increment to the next instruction. Dirt simple, but inefficient on the bus, and not ...
user16234's user avatar
  • 151
4 votes

BASIC09 and I-Code

The simplest way to get going with BASIC09 would be to get the NitrOS-9 "ease of use" edition. Then if you have a CoCo 3 with 512K RAM and a CoCo SDC (which lets you keep disk images on an SD card), ...
James Jones's user avatar
3 votes

Exit NitrOS9/OS9 EDIT command without saving file

While I am not familiar with OS9, I did read the linked PDF. As stated in the question's documentation quote, specifying input and output files upon opening the editor is optional. The edit will ...
Hitek's user avatar
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2 votes

BASIC09 and I-Code

The manual talks about it being a compiler, but I'm not sure I see significant differences between its I-code and tokenized BASICs in general. Well, so called 'tokenized' BASIC isn't really tokenized,...
Raffzahn's user avatar
  • 225k
2 votes

Length of leader block in Coco and Dragon cassette tape header and .cas tape image file format

I've made a couple of discoveries after a night's sleep. The CoCo still reads the leader length from a RAM address, but its address is two bytes higher in memory than in the Dragon 32: 0199 ** THESE ...
hippietrail's user avatar
  • 6,654
1 vote

Loading a Tandy CoCo or a Dragon 32 machine code program from cassette with multiple "name blocks"

Since the coco cassette interface used 1200 baud psk audio encoding in it, the tape format of the coco was 4X faster loading files from the tape and the tape files were 1/4th the size of similar files ...
Gary C's user avatar
  • 51
1 vote

How to connect a Tandy Color Computer to a Composite Monitor?

Or alternatively, you could have the awesome CoCoVGA installed in your CoCo2 and hook it up to any VGA monitor. It will add a plethora of colours and other options the original never had! http://...
Fedor Alexander Steeman's user avatar

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