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64 votes

What is this large device labelled 'Telefunken Datenspeicher' and how does it work?

It's a Demonstrator for an ALU and Memory. It's a serial ALU with registers, data path and a 6 byte storage, falling short to be a CPU. An ALU (German as well ALU, sometimes 'Rechenwerk') is a ...
Raffzahn's user avatar
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33 votes
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Why does the Commodore 64 have 4K of non-banked RAM at $C000?

I wonder why the Commodore 64 memory map was created as it was. As so often it helps to look at a machine's predecessor; in the case of the C64 that's not the VIC 20, but the Max Machine, a very ...
Raffzahn's user avatar
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29 votes
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Was there any computer since about 1960 without interrupt support?

The Wang 2200 series of minicomputers (Apr 1973 to Jul 1989) was implemented without hardware interrupts. All peripheral interaction was handled via polling. These machines were fitted with a BASIC ...
A. I. Breveleri's user avatar
26 votes
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First time seeing this odd little PCB inside a Playstation 2; What is it for?

This is the v4 PnP Key, an early solderless modchip that was used in combination with a swap disc to play import or backup games. There was also the v5/v6/v7 version that could be hooked to newer PS2 ...
olliebulle's user avatar
24 votes
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When did the PC bus start slowing access to video RAM?

This question starts with a number of misconceptions about early video, memory and bus systems that need to be addressed in order to clarify what this question really appears to be about. If you want ...
cjs's user avatar
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24 votes
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Is there a technical reason why Datel Action Replay on PC required a card?

Disclaimer: I always managed with Turbo Debug on games, which relied exclusively on software, and only used the amiga version of Action Replay. That said, the hardware Action Replay on PC gives it ...
Jean-François Fabre's user avatar
23 votes

Was AGP only ever used for graphics cards?

No, there was an AGP to USB card. The HP rp5000 Point of Sale system was launched circa August 2003 and includes this unique AGP card: The rp5000 has the (half-height) AGP card installed vertically ...
underscorePai's user avatar
23 votes

Was there any computer since about 1960 without interrupt support?

The first microprocessor, the Intel 4004, had no interrupt capability. Its successor, the 8008, had interrupts, but with the shallow call stack and the need to reserve scarce registers to do any sort ...
John Doty's user avatar
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22 votes
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How did Altair 8800 interrupts work?

I feel like I'm fundamentally misunderstanding something very important here, but the manual isn't much help. Yes, looks quite like it. The Altair is a very basic 8080 computer, so any handling is ...
Raffzahn's user avatar
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22 votes

First time seeing this odd little PCB inside a Playstation 2; What is it for?

That seems to be a modded PS2. The "12C508A" is a PIC often used in modchip boards for both PS2 and PSX. Sadly I can only find info about that specific modchip from other people asking about ...
kouta-kun's user avatar
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21 votes

Was there any computer since about 1960 without interrupt support?

Sharp pocket computers based on the ESR-H SC61860 micro-controller (PC-12xx, 13xx and 14xx) did not have interrupts. No instructions like rti, nothing. Everything was done by polling (it had for ...
Patrick Schlüter's user avatar
21 votes
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Atari SIO vs IEEE 488

IEEE 488 may look simple enough for a home computer ("It's just an 8-bit bus"), but is way more complicated than you might think: Lots of wires - A proper HPIB cable needs 24 wires and ...
tofro's user avatar
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20 votes
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What is the most accurate way to map 6-bit VGA palette to 8-bit?

The most accurate way of course depends on what is the purpose. No way is perfect and there is no one true method for all purposes. First of all, how the VGA works, is that it used the INMOS G171 ...
Justme's user avatar
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19 votes

Was there any computer since about 1960 without interrupt support?

Would embedded systems count? If yes, there were GI's PIC1600 MCUs (http://bitsavers.org/components/gi/PIC/1983_PIC_Series_Microcomputer_Data_Manual.pdf), predecessors of PIC microcontrollers by ...
lvd's user avatar
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18 votes

Atari SIO vs IEEE 488

According to Joe Decuir (one of the designers of the SIO bus), he wasn’t aware of another serial bus when he had to design a solution for external peripherals in a radio-silent system. Make of that ...
Stephen Kitt's user avatar
17 votes

What is this large device labelled 'Telefunken Datenspeicher' and how does it work?

A and B are two shiftable 8-bit registers. They form a serial ALU. U is the Überlauf-Register (carry). "Takt" is the clock signal. It shifts both registers, after 8 clocks the operation is ...
dirkt's user avatar
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16 votes

What are the electrical properties of the EAR and MIC sockets on a ZX Spectrum, and can they be connected between machines?

I'm revising this answer to suggest that yes, EAR to EAR communication should be possible without amplification. Read the edit history for my previous working. There's a large document on World of ...
knol's user avatar
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16 votes
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What contemporary hardware was available for the development of Atari 2600 (or other 2nd gen) games?

Since none of those early systems featured any custom designed CPU, generic development systems / In Circuit Emulators can provide all luxury needed. GI, first of those offered, beside cross-assembler ...
Raffzahn's user avatar
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15 votes

What is the most accurate way to map 6-bit VGA palette to 8-bit?

Justme detailed some of the reasons that the exact conversion method probably doesn't matter. Another reason is that you are probably going to interpret the 8-bit output according to the sRGB standard,...
benrg's user avatar
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15 votes

Gameboy Key Input Causes Crash

The modern compiler, or rather, the underlying libraries and build system that come with the compiling environment put some important code and/or data in the addresses FF80 and FF81 which you happily ...
Justme's user avatar
  • 33.7k
15 votes

When did the PC bus start slowing access to video RAM?

TL;DR: When the CPU-bus became faster than the I/O-bus Now, there are always going to be wait states during active scan line, because the video chip is using some of the video memory bandwidth for ...
Raffzahn's user avatar
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12 votes

Why did the Apple III have more heating problems than the Altair?

The absence of a fan was only part of the problem. (By the way, the Apple II also did not have a fan). [1] describes it like this: Those that did work initially often failed after minimal use thanks ...
dirkt's user avatar
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12 votes

What are the electrical properties of the EAR and MIC sockets on a ZX Spectrum, and can they be connected between machines?

There are actually two problems that need to be solved: The physically provided and expected signal levels on the EAR and MIC connectors are not symmetrical - The ZX Spectrum expects certain ...
tofro's user avatar
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12 votes
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What sort of LCDs are used by the Game Boy/TI-83 calculator/etc.?

The original Gameboy, which I assume this is about, is, as Wiki states a Reflective, 160 × 144 Pixels, STN LCD. Reflective means that it has no backlight nor other means of ilumination but simply ...
Raffzahn's user avatar
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12 votes

Was there any computer since about 1960 without interrupt support?

Lots of examples could be found among many of USSR era home computers based on the KR580VM80 chip (a clone of i8080). In a normal i8080 system, the CPU is supposed to work with companion (or 'chipset')...
lvd's user avatar
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12 votes

Is there a technical reason why Datel Action Replay on PC required a card?

Jean-François Fabre’s answer mentions a number of advantages of a hardware solution over software, but I think it’s worth expanding on the main reason (IMO): hardware can reliably generate an ...
Stephen Kitt's user avatar
12 votes
Accepted

How much extra did a color RF modulator cost?

An RF modulator is an RF modulator. It just modulates whatever signal you feed to it. There should be no difference between RF modulators that either can or cannot do colour, as it does not care if ...
Justme's user avatar
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11 votes

Was there any computer since about 1960 without interrupt support?

Although the Apple II family of computers allows I/O cards to use interrupts, none of the internal hardware on the Apple II nor the Apple //e offers any support for them beyond making the pins ...
supercat's user avatar
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11 votes

When did the PC bus start slowing access to video RAM?

The original CGA always imposed wait states on display memory accesses. The card's memory subsystem always performs one access every four pixel clocks, and only half of those are available to the CPU ...
supercat's user avatar
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10 votes
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Why did the Apple III have more heating problems than the Altair?

TL;DR: Basic Design Altair excels in thermal over the Apple III by two several basic points: Less Power to be Removed More Volume to Handle the Heat Transport Better Airflow to Remove Heat Power ...
Raffzahn's user avatar
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