tofro
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What are Holorydmachines?
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20 votes

Apparently, you are looking for Herman Hollerith and his Tabular Machines. Hollerith was the first to use punched cards for data storage (there were punched cards and tape before, but were mainly used ...

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What is the Kelly chip?
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20 votes

The question should rather be: "What could it have been?" - It never made it into an existing machine. According to some Internet lore, Kelly would have been the A3000+'s/AA3000's RAMDAC (digital ...

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Was there ever a microcomputer with a full-size keyboard and a hex numpad?
19 votes

Apparently you misunderstood the reasoning behind a hex keypad: It never was a means to ease input of hex characters, but rather the cheapest method to input anything at all. Early single board ...

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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?
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19 votes

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 ...

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What's the origin of terminating strings by setting the high bit of the last character?
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19 votes

The method was pretty common for small systems that had to do case-insensitive comparisons to user input or, simply, storage, of a lot of short strings (a standard case in BASIC interpreters). ...

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Last computer not to use octets / 8-bit bytes
19 votes

Such a question is a bit difficult, or rather impossible, to answer. While it is true that most mainstream computers today use units of 8 bits for bytes and and, at least Latin, characters, there ...

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Cloning circuit boards for antique computers?
19 votes

What you describe would be a possible way of replicating a vintage computer. The approach does, however, have some flaws that make it unlikely (or undesirable) to go this route, at least for designs ...

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How were Western computer chips reverse-engineered in USSR?
19 votes

You could reverse-engineer those early CPUs by grinding or etching away the top (plastic) layer of the chips down to the silicon die and examine the chip structures on an (optical) microscope. (...

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ZX Spectrum 48k Power Supply outputting 15V
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18 votes

This is relatively normal for the original PSU. The supply unit is a "soft" one that will output a much lower voltage under load when connected to the ZX Spectrum. 12 or even more Volts are ...

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Did any laptop computers have a built-in 5¼-inch floppy drive?
17 votes

The closest thing to a modern laptop that I'm aware of featuring an internal 5 1/4 drive is the Findex of 1979 which had a fairly complete (optionally battery-powered) CP/M computer including a hard-...

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How can I create a pipe for stdin/stdout of command.com (or 4dos.com) in C or a batch file?
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17 votes

MS-DOS doesn't support pipes like Unix does - It does support input and output redirection through its command line processor COMMAND.COM, but that's a different thing. If you're fine with pure I/O ...

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Has any major corporation ever successfully sued Microsoft for intellectual property theft?
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17 votes

Alcatel-Lucent won a lawsuit against MS in 2008 on a patent for audio file playback. That was later overruled by a higher court. Bristol Technology attacked MS for not revealing needed Windows ...

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Was Amiga the last of the home retrocomputers sold?
17 votes

If we are looking back to home computers, maybe the Q60 was the last real "Home computer clone", a Sinclair QL on steroids using a Motorola 68060 CPU in a PC case using ISA slots. It was first ...

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What PC "Clone" technology standards were introduced by clone manufacturers?
17 votes

Just two examples of the most important "standards" that came up during the PC's first years: One of the first and most common PC "standard" graphics card was the Hercules Graphics card that was ...

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Intel 386 multiply bug
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16 votes

Software can identify those early steppings on the 386 by checking whether the XBTS and/or IBTS instruction can be executed, since these instructions were dropped in later chip revisions. Software ...

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Alternatives for TurboVision on DOS
16 votes

This is not exactly a retro answer: The modern FreePascal compiler which is available for a lot of platforms (some even considered retro, like Amiga and PalmOS) comes with a library called FreeVision,...

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Weak bits on floppy for copy protection
16 votes

"Weak bits" are a means of copy protection that generates areas on a disk that read back as random values, without the floppy disk controller actually detecting an error. When copying such a weak bit ...

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How to at least partially read damaged sectors of floppy disk?
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16 votes

(Answer based on WD1770, a prominent standard Floppy Disk controller from ~1980) Standard Floppy controllers don't have any error correction at all. So there is nothing to switch off. They support a ...

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How did old computers address far more than 64K of memory despite only having a 16 bit address bus?
15 votes

There are a number of approaches that can allow a CPU with a 16-bit address bus to address more than 64kBytes of memory: Bank Switching - explained in another answer,basicaly switching for example 8- ...

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How can a peripheral work on both the ZX81 and on the ZX Spectrum?
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15 votes

The ZX printer is, like just about anything that carries the Sinclair label, a very minimalistic device - It only needs very few lines from the computer to actually work: Address bus: The printer ...

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Are later 68000 variants backward compatible with earlier ones?
15 votes

The 68k family is largely compatible between all the members. "Normal" application code can be written to easily run on all the members, unchanged. There are, however, a number of subtle differences ...

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What is the origin of different styles of assembly language mnemonics?
15 votes

Most probably it was the Z80 that actually tried to (and succeeded to) orthoginalize an already existing assembler language, that of the Intel 8080. 8080 assembly language used mnemonics that were ...

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Were there really any cost savings in Sinclair QL because of it being 8-bit design with 8-bit bus 68k CPU?
14 votes

By the time the QL was first designed (starting as a "ZX83" in early 1983), a full-blown 8MHz 68000 was not a mass-produced, cheap commodity item, but rather a pretty expensive beast to buy. ...

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How to use ISA card in modern PC
14 votes

There's basically two possibilities you may find: The ISA card is a fairly trivial piece of hardware, using I/O ports or memory-mapping only. In this case, it is pretty likely an USB-to-ISA or PCI-to-...

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Why didn't the 8086 use linear addressing?
14 votes

I am pretty sure the Intel engineers just weren't there, yet. And they were pressed by the market to push out a 16-bit CPU before all the others did to keep the market share they had already lost big ...

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Was the MC680x0's TAS instruction forbidden on Amiga systems only when operating in CHIP memory?
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14 votes

In order to detect whether the bus is "free" to access and it is safe to halt the CPU, take over the bus and access memory and peripherals, the Agnus and later DMA chips monitor the control bus for a ...

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68020 addressing mode suitable for page printing?
14 votes

The memory indirect [pre|post]indexed addressing modes were basically direct support on CPU level for 2-dimensional arrays (which are inherently suitable to describe printed (pixelated) pages in ...

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Why could you hear an Amstrad CPC working?
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13 votes

There seems to be a slight misunderstanding: The CPU in a computer is (almost) never doing nothing (excluding power save states which was largely unknown at times the Amstrad was en vogue). So there's ...

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What is the instruction set of the Z4?
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13 votes

Horst Zuse (Konrad Zuse's son, a computer science professor by trade) has a homepage where he supplies (and sells) various pieces of information, booklets and CDs and DVDs about his father's work. ...

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Why were 3D games on the Amiga not faster than on similar 16 bit systems like the Atari ST
13 votes

The thing the Agnus has that speeds up 3D games is the polygon fill feature. Blitting by itself is not so much a standard operation driving 3D performance. It can help 2D games and windowed GUIs a lot,...

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