Retrocomputing Stack Exchange
Retrocomputing Stack Exchange

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1500 questions
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2 answers

Why did pressing the joystick button spit out keypresses?

If you pressed one of the joystick buttons on the TRS-80 Color Computer while running BASIC, it would act as if @ABCDEFG were typed. Pressing the other joystick button would similarly type out HIJKLMNO. Why did the CoCo exhibit this behavior?
DrSheldon
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Looking for an old image of designing a CPU with plan laid out / being edited on a literal floor

There is an image that I remember seeing, but that I have never been able to find. It shows 2-3 people on their hands and knees, crawling around a blueprint of a chip that had been rolled out over the floor of a room. Presumably this was from before…
Craig Gidney
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1 answer

ZSPL language, anyone heard of it?

While reading the Byte sieve article (Gilbreath 1981), I came across a language I have never heard of, ZSPL. I suspected this was actually a specific version of another language, perhaps PL/1. However, the listing shows it most closely resembling…
Maury Markowitz
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3 answers

Is there a way to get a compiler for the original B programming language?

I am learning about the original B programming language, but I don't have a compiler. Is there an emulator for an old computer that can run an old operating system that have a compiler for the original B programming language?
user13493
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6 answers

Did scanlines appear on the ZX Spectrum screen?

I used played Spectrum games as a child. According http://scanlines.hazard-city.de/ and http://www.zxdesign.info/vidresearch.shtml, the Spectrum 48K emitted 50Hz half-resolution full frames, instead of interlaced ones (also the 128K, though some…
ron
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How does a biquinary adder work?

I whipped together a quick answer to this question and then realised, that I have no idea how these tubes manipulate the numbers. A binary adder is easy to understand to the modern mind; for each bit you can use an XOR for the result, and an AND for…
Omar and Lorraine
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1 answer

How were Zuse Z22 Instructions Encoded?

The title says it all: How to En-/Decode Z22/Z23 Instructions? (History and Linkage: The question was raised by Wilson in a comment on my answer to his question "Why are PDP-7-style microprogrammed instructions out of vogue?", where I mentioned the…
Raffzahn
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Was the picture area of a CRT a parallelogram (instead of a true rectangle)?

This may seem like an absurd question at first, but I've been giving it some thought and I'm genuinely curious about the design details of these devices. I was reading an answer on an unrelated Stack Exchange site about the retrace/flyback details…
smitelli
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2 answers

Why did some CPUs use two Read/Write lines, and others just one?

Many 8-bit processors, such as Motorola's 6800 and MOS Technology's 6502 make use of a single pin to indicate to the rest of the system whether the CPU wishes to read from or write to a memory location (e.g. logic high = read, logic low = write).…
Kaz
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Measuring frame length on the ZX Spectrum

I've seen some small utilities for the ZX Spectrum, such as FUSETEST and MINFO, that report the number of T-states per frame. I can see these utilities don't rely on ROM checksums or anything like that to find out what machine they are running in…
mcleod_ideafix
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What is this code on the zero page that was put there by the BASIC ROM?

(question copied from SO (from the days before RC.SE existed): http://stackoverflow.com/q/31877835/477476) Zero-page memory maps of the PET that I've found claim that the zero page address range$00C2..$00D9 are used for static data, e.g.…
Cactus
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4 answers

For fast scrolling DOS games, when was Mode13h preferred over Mode X?

Back in the DOS days of gaming (more specifically, 80286 - 80486 era), developers typically needed to choose between using the chunky and easier Mode 13h or the more complex "Mode X" that provided hardware scrolling and VGA memory-to-memory…
cbmeeks
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Are NES turbo buttons internal to the controller?

As you may know, the classic NES controller was not the only NES controller that Nintedo released with the NES. These included the NES advantage, the NES Max, and the Dogbone. All of these new controllers featured turbo buttons (buttons for frame…
Badasahog
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How do accelerators and CPU cards work on the Apple II?

An Amiga 1200 exposes the entire CPU bus on the expansion port, so that an accelerator only needs to assert BR which causes the onboard CPU to stop all computation and electrically disconnect from the bus entirely, and then wait for BG which should…
Omar and Lorraine
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Powering up my ZX Spectrum

I have also found a nice ZX Spectrum laying around. It needs a power source of course to run but there seems to be none that can be used to power it. Google doesn't seem to help and I would love to be able to use a machine that can be used... Is…
Anthony Pham
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