Chromatix
  • Member for 3 years, 9 months
  • Last seen more than a month ago
  • Helsinki, Finland
Why were relays prevalent in early 1940s computers when vacuum tubes were also available?
60 votes

Using relays to implement logic functions was already quite well understood at that time, and in fact the Post Office type relays were designed to do just that as part of the telephone system. The ...

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Why was the return key symbol ⏎ drawn differently from the motion of a CR-LF?
52 votes

Even though the CR usually goes before the LF in ASCII text, most printer mechanisms actually perform the LF before, or during, the CR. So the shape of the arrow is actually accurate. This is even ...

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Why were optical drives not used as secondary storage instead of magnetic drives?
Accepted answer
49 votes

For the simple reason that until relatively recently, it was very difficult to make a rewritable optical medium, but it was easy to make a rewritable magnetic medium. Magnetic tape as a recording ...

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When did compilers start generating optimized code that runs faster than an average programmer's assembly code?
36 votes

For a start, it is widely known that FORTRAN II for the IBM 1401 series was specifically designed to generate high enough quality object code to make assembly programming of numerical routines ...

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Why did the IBM PC have an internal power supply?
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35 votes

Internal power supplies, while not universal, were not unusual at the time. The major considerations were cost, ease of design, and safety (that is, passing safety regulations that already existed in ...

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What did the "programs" that "human computers" executed look like?
34 votes

Every ship at sea carried such a human computer, in the person of the navigator. He followed a number of such "programs", properly termed algorithms, taken from Nathaniel Bowditch's seminal ...

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Did the 68000 separate A/D registers save circuitry?
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30 votes

Each of the 68K series CPUs had dedicated address-generation hardware which was wired more directly to the A registers and had only limited access to the D registers. Conversely, the main ALU was ...

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How fast were BASIC interpreters in the 80s? (Is this optimization for speed really necessary?)
27 votes

You can actually try out these programs on a real-speed computer of that vintage using jsBeeb or, for a more convenient program editing environment, bbcmic.ro. To make the above programs compatible ...

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3 beeps on a 486 computer with an American Megatrends bios?
Accepted answer
26 votes

Here is a reference to BIOS beep codes. For American Megatrends, look under AMI. 3 beeps means the low 64K failed - a very basic test - which probably means the RAM isn't working at all. You ...

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What is DRAM refresh and why is the weird Apple II video memory layout affected by it?
25 votes

DRAM requires that each row of the memory is read and re-written regularly, at least every few milliseconds for the devices available at the time the Apple II was designed. This contrasts with the ...

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Why does PAUSE key have a long make code and no break code?
Accepted answer
25 votes

In scancode set 2, the "break" scancodes consist of the "make" scancodes prefixed by F0. This is consistent across nearly all the keys. Some keys include a modifier prefix in the Ex range as well, ...

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How did the "Programmer's Switch" work on early Macintosh Computers?
24 votes

The "programmer's switch" is more technically known as the NMI (Non Maskable Interrupt) switch. It is mapped to a priority 7 interrupt on the 68K CPU, which means it is capable of ...

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Was it possible to write a novel on a BBC Micro 16kb/32kb memory era computer without expansions?
24 votes

It was common to install word processing software as a ROM into one of the spare "sideways ROM" sockets on the BBC Micro, in the same way as the DFS ROM needed to operate a floppy drive. ...

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Why the change in layout of single and double precision in floating-point registers?
Accepted answer
23 votes

When you have a small transistor budget, it is considerably easier to design your circuitry around a single representation format - the most capable one - and treat converting other formats to and ...

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Could you create a loop in direct-mode with BASIC?
21 votes

In any BASIC variant that allows multiple statements on one line, the multiple statements that are required to implement a FOR-NEXT or REPEAT-UNTIL loop can be provided in immediate mode. Many 8-bit ...

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How did 68k-based Macs (or other contemporary systems) detect how much RAM was installed?
Accepted answer
20 votes

Yes, part of the POST sequence (which occurs before the display lights up) is a simple memory test which also serves to detect how much RAM is present. The Mac then sets up the hardware and its ...

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Why was "C:" chosen for the first hard drive partition?
19 votes

The letters A: and B: were reserved by MS-DOS, which was essentially a clone of CP/M and followed its usual practice, for floppy disk drives. If only one such drive was fitted, both letters were ...

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Why is the keyboard and cellphone / telephone numbers in a different order?
19 votes

Both keypads are in numerical order. However, in a computing context, the correct order is 0,1…9, but in a telephonic context, the correct order is 1…9,0 - because the latter is really a ten, not a ...

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Was it possible programmatically to manipulate the volume as well as the pitch on computers with no sound chip?
19 votes

I think the best you could do in some cases was alter the pulse width of the basic square wave the hardware could produce. That wouldn't really change the volume, but you could make the tone "thinner"...

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Are the 6809 and 6809E different from a programmer's point of view?
Accepted answer
18 votes

To directly answer the question: there is no difference whatsoever on the software side. The CPU core and indeed the die inside the package is exactly the same, just different pins are bonded out in ...

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9-pin vs 10-pin serial port ribbon cables
Accepted answer
17 votes

In more recent designs, since the mid-2000s I think, it became common to include "key" pins like this to reduce assembly errors. In most cases the pin removed was non-essential in the first ...

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What was the 1 MHz bus used for on the BBC micro series?
Accepted answer
17 votes

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 ...

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How did the Rush 3D engine in Crazy Taxi: Catch a Ride work?
17 votes

I don't have knowledge of the Rush 3D engine itself, but I used to work for a company that made software graphics engines, so I can speak in general terms about how they're likely to work. The GBA has ...

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x87 trigonometric instructions
Accepted answer
17 votes

The tan(x) function has a period of π radians, with asymptotes at ±π/2; it effectively calculates sin(x)/cos(x), and the latter goes to zero at those points. So a function which evaluates properly ...

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Cost of unrestricted sprites
Accepted answer
17 votes

Hardware of this sort has to be able to cope with the worst-case scenario in any given dot-clock cycle. So it has to look at the top layer pixel, determine whether that is transparent, and if so go ...

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Do the holes in Jacquard loom punched cards represent input data or program code?
17 votes

Program code for modern CPUs, in practice, consists of opcodes which tell the CPU what operation to perform, and operands which provide data to operate on. In RISC CPUs these are necessarily both ...

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What really is a sound card driver in MS-DOS?
16 votes

Most PCI soundcards do not have hardware support for games and other applications that expect a SoundBlaster or AdLib to be present. Older cards made a special effort to provide what's known as "...

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Can special tools recover data from floppy disks when Windows Explorer fails to do so?
16 votes

It sounds like some blocks on the disk (particularly the ones containing directory information) are okay, but some (containing some file data) are not. This is a data recovery situation. If you boot ...

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What does it take to recreate microchips like 68000 and 6502 in their original process nodes nowadays?
16 votes

It should be feasible to manufacture NMOS-process parts using 0.6µm equipment that is still in current use. WDC's W65C02S, as well as their other current products, are made at TSMC on 0.6µm, though ...

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How slow was the 6502 BASIC compared to Assembly
16 votes

Most implementations of BASIC for 8-bit home computers were interpreters, and in that sense they're similar to the standard versions of Python. You could typically expect simple programs to run 100 ...

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