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63 votes
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Why are C64 games inconsistent with which joystick port they use?

As Wilson points out in his answer, it has to do with how the CIA chips interact with the keyboard and the joystick ports, and the confusion that can arise trying to determine where input is being ...
Geo...'s user avatar
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56 votes
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Why did SCSI require so many pins?

SCSI, I think, is a serial interface. No, it isn't. SCSI das defined as a parallel interface for high speed data transfer. Though there are modern incarnations using serial transfer, while being ...
Raffzahn's user avatar
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24 votes

Were there any parallel port keyboards?

Of the variants produced in a relatively large series - let me remind you about the keyboard connection on the Commodore 128D - it was connected using a 25-pin interface, 23 lines of which directly ...
Wheelmagister's user avatar
24 votes

Were there any parallel port keyboards?

Early Wang basic computers used a backplane keyboard with an enormous bespoke parallel interface to the detached style keyboard device. Wang's 2200 and 2600 BASIC-only minicomputers were available ...
A. I. Breveleri's user avatar
24 votes

Why are C64 games inconsistent with which joystick port they use?

Because of the way that the joystick port 1 is mapped to the same hardware as the keyboard, from the software's point of view it's impossible to tell if you're wiggling the joystick or typing ...
Omar and Lorraine's user avatar
23 votes

How did Joysticks with more than 4 buttons and all those extra features work on a Game Port?

I know of a minimum of two implementations of this that, as far as I know, were done independently. Gravis's GrIP protocol, which is used in the gameport version of the Gravis Gamepad Pro. Wikipedia ...
ssokolow's user avatar
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19 votes
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What was the 1 MHz bus used for on the BBC micro series?

The so-called "1MHz bus" is not actually a separate bus. It is just the set of devices which were too slow to run at the full 2MHz in the original BBC Micro, and which therefore incur a ...
Chromatix's user avatar
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19 votes

Why do some Atari ST motherboards include many Inductors?

They are not really inductors. They are EMI noise filters for suppressing electromagnetic interference that conduct out of the unit via the wires. These kind of EMI filters usually have two ferrite ...
Justme's user avatar
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19 votes
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If a PS/2 device on a 32-bit x86 sends a byte to the IO port 0x60 and you read it, what happens next?

On standard PCs, the main CPU and PS/2 controller use a handshake mechanism in the status register at port 0x64: Main CPU wants to read (probably because it received a keyboard interrupt): Read port ...
tofro's user avatar
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17 votes

How did Joysticks with more than 4 buttons and all those extra features work on a Game Port?

There are multiple different ways that are possible, so many of the things you listed have been used, in addition to others. Your first question is, how did they do this. Specifically, the Microsoft ...
Justme's user avatar
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15 votes
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Is the NES controller port identical to the port on a Wii remote?

The two consoles do have different controller ports. The NES Classic Edition is not directly compatible with original NES controllers, but it does work with the Wii Classic Controller. The original ...
libertyernie's user avatar
15 votes
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What are the electrical characteristics of a PC gameport?

The documentation for IBM's original Game Control Adapter has some details that will be of use. Even though you're using a SoundBlaster card instead, it should still be compatible with the IBM ...
Kaz's user avatar
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15 votes
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Could the BBC micro's analogue input be used to sample sound?

No, it can not be used to sample audio. As the link you provided says, in 12-bit mode it takes 10 milliseconds to convert a sample, and even in 8-bit mode it takes 4 milliseconds. That results into ...
Justme's user avatar
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15 votes
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Why do some Atari ST motherboards include many Inductors?

There are versions of the Atari 520ST, and perhaps the 1040ST, that differ in having many discrete inductors attached at the I/O port lines for serial, parallel and floppy ports. Essentially all ...
Raffzahn's user avatar
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15 votes

If a PS/2 device on a 32-bit x86 sends a byte to the IO port 0x60 and you read it, what happens next?

There is not only one place in memory, and it is not even memory. The port 0x60 is an IO port in the CPU IO address space for accessing the keyboard controller data port. It is used to access a lot of ...
Justme's user avatar
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11 votes

What 8-bit microcomputer systems multiplexed multiple physical ports on a single controller?

The Sinclair QL also had two RS232C ports which used an unusual combination of a ASIC (ZX8302) and Intel 8049 to provide two physical ports (with non standard connectors) but could not be used ...
GrantB's user avatar
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11 votes
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How did the BBC sideways ROM software for the AMX mouse process the user port input data to determine x and y movement?

Trying to get more into the specifics of the BBC connection, there is a substantial hint in the user guide: However only 5 bits of the [user] port, and CB1, CB2 are used: This leaves bits 1,3 and 4 ...
Tommy's user avatar
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10 votes

Were there any parallel port keyboards?

Early micro/home computer used parallel keyboards. These were (usually) called 'ASCII' Keyboards. A good example is the Apple II, which implements a protocol almost exact like you imagined - sans ...
Raffzahn's user avatar
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10 votes
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What is this port?

That would be USB, Audio out, Microphone in, FireWire. And PCMCIA slot above the two connectors. And there is a connector for a docking station at the bottom.
Justme's user avatar
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10 votes

Did the PAL version of Super Mario Bros. on the NES really have faster music, and if so, why?

Porting a game to PAL while making all actions take the same number of frames would cause the game to perform 20% slower than with NTSC. Some games did this, but other games adjusted the amount of ...
supercat's user avatar
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9 votes

Why did SCSI require so many pins?

Then why did SCSI require so many pins? Differential signaling. The original standard was actually a 25-pin system using an 8-bit parallel signal going in one direction only. There was a separate ...
Maury Markowitz's user avatar
8 votes

Did the IBM Game Control Adapter have I/O port aliases?

The original IBM PC and AT designs allocated 10 bits for I/O addressing, and only decoded address lines A0-A9 for on-board I/O devices. However there was no physical limitation to 10 bits, so a card ...
Bruce Abbott's user avatar
  • 6,693
8 votes

Did the PAL version of Super Mario Bros. on the NES really have faster music, and if so, why?

Just came across this while researching NES PAL music. What nobody has mentioned is there were two European releases. The original 1987 launch version (distributed by Mattel in the UK) was a direct ...
Fryguy64's user avatar
7 votes

What are the electrical characteristics of a PC gameport?

back in the (x386) days I was using GAME port as an ADC for home made scanner and other self build HW. As it is usual during development there is occasional set back like short circuit etc. The GAME ...
Spektre's user avatar
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7 votes

Why are C64 games inconsistent with which joystick port they use?

In addition to what already was stated, namely: ... how the CIA (Complex Interface Adapter) maps JoyStick - or in general, any - input: The signals a (digital) JoyStick delivers, come in via Pins 1 ...
Leahpar Suidualc's user avatar
7 votes

Which home computer first included a printer and modem port as standard?

According to this page the Sol 20 included: Ports: serial, parallel, cassette and according to Wikipedia: Cassette, parallel and serial ports extended off the back of the motherboard into holes in ...
manassehkatz-Moving 2 Codidact's user avatar
6 votes

Were there any parallel port keyboards?

For a keyboard that includes a shift key to be useful, either the CPU must poll it often enough to observe the state of the shift key whenever another key is pushed, or the keyboard must capture ...
supercat's user avatar
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5 votes

How did the BBC sideways ROM software for the AMX mouse process the user port input data to determine x and y movement?

I don't know the specific details, but in general the mouse uses standard quadrature encoders so for each axis you get two data pins that output movement data. While several ways to decode the ...
Justme's user avatar
  • 33.7k
4 votes

Were there any parallel port keyboards?

The LINC (Laboratory Instrument Computer), the first computer I programmed in 1965, had a one-key rollover. When a key was pressed on its Soroban Engineering keyboard, a solenoid locked that key down ...
David Spector's user avatar
4 votes

What are the electrical characteristics of a PC gameport?

There is no official specs for game port current limit. Some adapters may have resistors, ferrite beads or fuses for current limiting, but usually a short circuit still fries something (except for a ...
Justme's user avatar
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