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31 votes
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Why did pressing the joystick button spit out keypresses?

On the Color Computer, I/O address &FF00 is used for both the joysticks and the keyboard row input. Bits 0/1 are toggled by the two joystick port buttons, and these bits are the same as rows 1/2 ...
Brian H's user avatar
  • 60.8k
14 votes

The Tandy/TRS-80 Multipack Interface (MPI)

From Marty Goodman, writing in The Rainbow, January 1987, page 102: The reason for the Multi-Pak fix for the CoCo 3 is at least twofold. First, the older PAL chips used to decode the software slot ...
tlindner's user avatar
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14 votes
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Expansion port on the Color Computer

There are two variations of the cartridge port on the Color Computer lines. The attached image shows the pin out of the CoCo 2 & 3. The CoCo 1 cartridge port is slightly different, in that it ...
Brian Blake's user avatar
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14 votes
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What format is used for CoCo cassette tapes?

Most of this info comes from the Color Computer 3 Service Manual (26-3334), except for the actual frequencies used on the cassette: On the tape, frequency shift keying is used, with a zero bit ...
Michael Hampton's user avatar
14 votes
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What is the CoCo "Head Banger bug" and what is the "fix"?

I posted this question because I had those thoughts, and then spent ages going through multiple dead ends until I finally found it (my Google-fu is on the fritz). So that I don't have to go through ...
John Burger's user avatar
  • 1,325
14 votes

Ideal resolution for color computer on PAL/SECAM

In the early 80s, cost of RAM for the framebuffer was the dominant factor, closely followed by RAM bandwidth. The difference in resolution between NTSC and PAL systems is minimal in comparison to ...
occipita's user avatar
  • 2,367
13 votes
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Is NitrOS-9/OS-9 a preemptive multitasking environment?

Yes, it is pre-emptive. See: https://sourceforge.net/p/nitros9/wiki/The_Kernel/#multiprogramming In particular, it uses the 60 Hz interrupt to switch between active processes with the same priority....
George Phillips's user avatar
13 votes
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Calculating the time for a CPU cycle

It's one divided by the clock. So for 0.895 MHz divide 1 by 895000 and the answer is 1.117318 micro seconds. for 1.79 Mhz it's 558.6592 nano seconds. I suspect however that the clock will be some ...
PeterI's user avatar
  • 5,297
13 votes
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Color BASIC RND function not so random

From here it looks like the official way is to use RND(N) to seed, where is N is a negative number. But according to this you can also just copy a byte from a timer to the RND seed with: POKE 280,...
Nick Westgate's user avatar
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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11 votes
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What are the options for installing a 6309 in a TRS-80/Tandy Color Computer

Your first option is to remove the 6809 from the CoCo. Some CoCo 1 and 2 models, all you have to do is remove the CPU from a socket and put a new one in. Other CoCo 1 and 2 models, and all CoCo 3 ...
Brian Blake's user avatar
  • 1,731
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
  • 60.8k
10 votes

The Tandy/TRS-80 Multipack Interface (MPI)

Tim's answer referencing Marty Goodman offers a good explanation, but not really any options for users today who might need to make this upgrade. The 3024 model can be modified with a simple PAL ...
Brian Blake's user avatar
  • 1,731
9 votes

Ideal resolution for color computer on PAL/SECAM

What would be the ideal resolution? There is no "ideal" resolution. TV screens use "overscan", which means that the full TV image is occluded by a bezel. That doesn't matter for ...
dirkt's user avatar
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8 votes
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Differences in disk storage between systems

The major difference between drive speeds in classic computers is the philosophy and design of the drive and it's attachment mechanism. Some computers, such as the TRS-80/CoCo and Apple II lines, ...
Payton Byrd's user avatar
  • 1,053
8 votes
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CoCo Max Mouse Cartridge

I found a lovely answer on page 54 of "Color Computer 1/2/3 Hardware Programming" by Chris Lormont. The joystick and button values are found by reading addresses $FF60 - $FF63. The first time an ...
tlindner's user avatar
  • 2,367
8 votes
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Extended Color BASIC TIMER Function

The CoCo has an interrupt called fast interrupt (FIRQ) which is connected to the video output horizontal sync pulse. The IRQ happens every 1/16 of a millisecond (62.5 microseconds). The extended basic ...
Paulo Garcia's user avatar
8 votes
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What are the advantages of NitrOS-9 over OS-9?

The documentation generally does apply correctly between OS-9 and NitrOS-9. To understand the advantages over OS-9, it is good to look back that the different eras of the project. In the beginning, ...
tlindner's user avatar
  • 2,367
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
7 votes
Accepted

Can someone help me get xROAR to read files? (M6809/TRS-80 ColorComputer)

You can manage CoCo disk images quite easily with MAME's imgtool. I've assumed you want to use RS-DOS on a CoCo 2, launching xroar via: xroar -default-machine coco2bus To make a blank, single-sided ...
scruss's user avatar
  • 21.7k
7 votes

Why did pressing the joystick button spit out keypresses?

The fewer kinds of input a computer has to deal with, the easier its life is. This applies equally to physical ports and to the provisions for input in the BIOS and operating system generally. ...
Martin Kochanski's user avatar
7 votes

Ideal resolution for color computer on PAL/SECAM

If this is about connecting the color computer to television antenna input via an RF modulator, then the local TV system variant matters, as both the RF modulator for the computer and the RF ...
Justme's user avatar
  • 33k
6 votes
Accepted

Color Computer Expansion port "listening" bus

For the ZX Spectrum there is a project called ZX Pie. AFAIU this is a TK-Pie application. As the name suggests, it's a board attached to the ZX Spectrum's expansion slot that 'listens' the Address ...
Raffzahn's user avatar
  • 224k
6 votes
Accepted

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

Disto Super Controller II

According to this gem Tandy's Little Wonder, The Color Computer 1979-1991, When OS-9 came out a flaw was quickly discovered in the Tandy disk controller (and all others made at that time). ...
Aaron's user avatar
  • 2,384
6 votes
Accepted

Disto Super Controller II

While in normal mode, the SCII (and the Tandy and other manufacturers' controllers) would not buffer data. The CPU would wait as the drive would read and write data to and from the computer's memory. ...
Brian Blake's user avatar
  • 1,731
5 votes

Breaking the CoCo 3 32K Cartridge Barrier

I would make the assumption that, in the CoCo 3's case, a 32k, 64k or 128k ROM can be created. According to the discussion on the CoCo Mailing list, the normal size is a little less than 16k or 32k. ...
Brian Blake's user avatar
  • 1,731
4 votes

What are the options for installing a 6309 in a TRS-80/Tandy Color Computer

If your lucky enough to have a socketed Microprocessor from the factory, the process is removing the old chip and installing the new chip. You do have to make sure your new 6309 is the E version, E ...
tlindner's user avatar
  • 2,367
4 votes

Digisector DS-69 video digitizer

The manual asks for a "tee" connector - that's a simple wire connection without any logic inside (and equivalent to monitor passthrough that's also supported). You can safely use an Y-cable instead.
Kuba Tyszko's user avatar
  • 2,648

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