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Why were early personal computer monitors not green?

Green was traditionally the most common color for computer monitors; it combines strain-free readability with low cost. Given this, it's surprising that the first versions of the Commodore PET and ...
rwallace's user avatar
  • 62.4k
30 votes
2 answers
3k views

Process model in early UNIX

I heard recently that the process model in very early variants of UNIX was quite a bit different to the fork/exec model used nowadays. How did it differ from the current state?
user avatar
30 votes
3 answers
4k views

What was the first operating system to feature a separate kernel?

Kernels are programs that abstract the hardware of a computer to some extent, allowing other programs to use standardised system calls (e.g. malloc) to perform hardware tasks (e.g. writing to memory, ...
wizzwizz4's user avatar
  • 18.7k
29 votes
1 answer
34k views

Why do 3D models on the PlayStation 1 “wobble” so much?

A memorable part of the PlayStation 1 experience was “wobbly” 3D graphics, where (supposedly) straight edges would warp, jitter and pulse as the camera panned across a scene. This was especially ...
jamesfmackenzie's user avatar
29 votes
4 answers
3k views

Did Apple really advise customers to lift up and then drop their computers?

This led to the infamous technical note where Apple recommended users facing problems with the Apple III to lift the computer two inches and then drop it, as this would set the circuits back in place.[...
snips-n-snails's user avatar
29 votes
3 answers
6k views

Magnetic exposure to floppy disk damages file system and requires complete reformat?

What I noticed is, that formatting a floppy disk takes three times as much time for the same data amount as writing a file to the disk normally. The accoustically perceivable jumps of the head between ...
neverMind9's user avatar
  • 1,749
29 votes
3 answers
3k views

What's the TUBE interface of the BBC micro all about?

I keep reading of the BBC micro's tube interface that was apparently designed as a co-processor interface to the 6502. I would be interested in what were actual applications of this interface and ...
tofro's user avatar
  • 35.2k
28 votes
4 answers
17k views

How did 8 bit processors perform 16 bit arithmetic?

How did 8 bit processors such as the Z80 and 8080 perform 16 bit arithmetic? They have an 8 bit data bus, so how does the ALU perform 16 bit arithmetic on the register pairs? Z80 architecture diagram ...
Jet Blue's user avatar
  • 2,005
28 votes
4 answers
7k views

Unix Haters Handbook - guaranteeing synchronous, atomic operations

I've come across Filesystems with versioning and have been reading through the Unix Haters Handbook, linked there. I came across page 85: On the other hand, techniques for guaranteeing synchronous, ...
Mr Redstoner's user avatar
28 votes
7 answers
7k views

Over its lifetime, how many Apple II computers were sold?

It would be nice to break it down by model if possible.
nevster's user avatar
  • 1,048
28 votes
4 answers
5k views

What's the relationship betweeen MS-DOS and XENIX?

Browsing MS-DOS sources on GitHub, I often see mentions of XENIX: DOSSYM.ASM: ; XENIX calls all return error codes through AX. If an error occurred then the ; carry bit will be set and the ...
Igor Skochinsky's user avatar
27 votes
4 answers
1k views

How to get rid of yellowing in plastics?

I have some old electronics with white plastic that's starting to turn yellow. I know it's caused by flame retardants, UV rays, and so on. How can I restore my electronics to their former color?
snips-n-snails's user avatar
27 votes
3 answers
12k views

How does the Gameboy's memory bank switching work?

I'm writing a Game Boy emulator, but I don't completely understand how its memory mapping works. Here is what I (think) I know (and don't know). The CPU can address up to 0x10000 memory locations ...
dav's user avatar
  • 1,069
27 votes
4 answers
4k views

Use of undocumented opcodes

I figure this is fitting for Retrocomputing.SE because CPUs like the 6502 and Z80 and the PDP-8, and probably others, have undocumented instructions and will happily execute them, in contrast with ...
Omar and Lorraine's user avatar
27 votes
17 answers
8k views

How much did the first hard drives for PCs cost?

I would like to know how much early PC hard drives cost but have only been aable to find adjacent or unsourced data. According to the Centre for Computing History: The "IBM 5161 Expansion ...
Ellen Spertus's user avatar
27 votes
9 answers
3k views

What were the applications of 5/6-bit serial port formats?

Traditional PC serial ports, based on members of the 8250/16550 UART families (or their clones within SuperIO chips) support some unusual serial data formats, specifically 5- and 6-bit data, and 1.5 ...
user avatar
27 votes
8 answers
6k views

Why did 8-bit Basic use 40-bit floating point?

Nowadays floating point is usually either 32 or 64 bits, sometimes 16, occasionally 128. But of course, the Basic interpreters on the 8-bit machines, having to implement floating point in software ...
rwallace's user avatar
  • 62.4k
27 votes
4 answers
4k views

Why did the Atari 800 designers choose such a radical system design?

The physical system design of the Atari 800 was pretty radical, when compared to the 3 other canonical home computer designs of the late-1970s: TRS-80 Model 1, PET, and Apple ][. As the photo of the ...
Brian H's user avatar
  • 60.8k
26 votes
4 answers
5k views

Cleaning 5¼" floppy drives

Going to the store is treacherous for me. So I prefer doing stuff at home, including cleaning up 5¼" floppy disks with only home supplies. Unfortunately, I do not know how or which materials/chemicals ...
Anthony Pham's user avatar
  • 2,474
26 votes
10 answers
8k views

Graphics chips in 1980

Suppose you were trying to build a computer with a color graphics display in 1980, you have limited engineering resources and time to market is critical, so you want to get as many of the parts off ...
rwallace's user avatar
  • 62.4k
26 votes
12 answers
5k views

Why did CP/M and MS-DOS use the BIOS instead of their own drivers to access hardware?

Modern versions of Windows (and other modern operating systems I suppose) have their own drivers to access hardware. But as I have read, in the old days, if CP/M or MS-DOS wanted to access hardware, ...
user7681202's user avatar
  • 1,857
26 votes
5 answers
3k views

Why did the stock Amigas not have a battery for keeping the time/date?

The Amiga computers were advanced machines meant to do all sorts of things, including file management. They had a GUI OS (Workbench) and everything right from the very start. They were not some games-...
Superfrog's user avatar
  • 261
25 votes
3 answers
885 views

Why was segment register value scaled by such a small factor of 16 on i8086?

In 8086 architecture memory is addressed by segment:offset scheme, where the 20-bit linear address is formed as address=segment*16+offset. This looks needlessly complicated and doesn't allow to ...
Ruslan's user avatar
  • 1,444
25 votes
1 answer
5k views

Why do all the Speech Synthesizers have that same Voice?

The first time I ever played with software speech synthesis on a microcomputer (not hardware synthesis, like in TI's Speak & Spell) was around 1983, using S.A.M for the Commodore 64. A year later,...
Brian H's user avatar
  • 60.8k
25 votes
1 answer
4k views

What is 'Adaptive Tile Refresh' in the context of Commander Keen?

The question Did John Carmack really invent "Adaptive Tile Refresh"? asks about the origins of the scrolling and drawing techniques used to allow an MS-DOS PC to provide a NES console-like ...
knol's user avatar
  • 12.5k
25 votes
3 answers
7k views

Why does DOS ask for the current date and time upon booting?

In most versions of DOS, when they are started from a medium that lacks an AUTOEXEC.BAT file, the very first thing COMMAND.COM does is ask the user to confirm the current date and time: Starting PC ...
user3840170's user avatar
  • 23.1k
24 votes
8 answers
12k views

Why is the Intel 8086 CPU called a 16-bit CPU?

Based on my understanding, the bitness of a CPU specifies how much memory it can address (which is determined by the size of the CPU's address bus I guess). For example: a 32-bit CPU can address 232 ...
user14660's user avatar
  • 273
24 votes
4 answers
2k views

Was the design of MS-BASIC for 6502 based on MS-BASIC for 8080?

Looking through the source code of the 6502 MS-BASIC, certain parts of it seem more reminiscent of how things would be done on the 8080 than on how they should be done on the 6502. Code to find a ...
supercat's user avatar
  • 37k
24 votes
3 answers
1k views

How can you measure time using BASIC on Atari XL computers?

Some time ago, I benchmarked some 8-bit computers to find out the fastest BASIC interpreter. I ended up using the classic SAXPY benchmark, as I didn't want any I/O overhead to fool the measurement: ...
mcleod_ideafix's user avatar
24 votes
3 answers
7k views

What causes the glitchy sound when a GBA cartridge is removed?

Example in mGBA (mirror) — SOUND WARNING. When you remove a game cartridge from a powered-on GBA, it makes this horrible, loud glitching sound. I can tell that a small portion of the looped sound is ...
leetbacoon's user avatar
23 votes
6 answers
4k views

ZX Spectrum tokenisation

The BASIC used in the early ZX Spectrum (and also its ZX predecessors) had this weird thing where every single BASIC token was printed onto the keyboard, and for example PRINT or LOAD were entered by ...
Omar and Lorraine's user avatar
23 votes
5 answers
6k views

Why did mainframes have big conspicuous power-off buttons?

Some fascinating stories in this discussion thread. It starts with discussion about computers overheating, but about halfway through the thread, it switches to discussion of mainframe installations in ...
rwallace's user avatar
  • 62.4k
23 votes
4 answers
7k views

Why not one pixel per color clock?

Early home computers and game consoles output video to TV sets. The NTSC color clock frequency is 3.58 MHz. This informed the design of some video systems: http://pineight.com/mw/index.php?title=...
rwallace's user avatar
  • 62.4k
23 votes
3 answers
4k views

What were the actual memory model definitions in MS-DOS?

I've heard the phrase "memory model" used in relation to MS-DOS programming (and early Windows), with terms such as "small" and "compact". But what were the actual ...
paxdiablo's user avatar
  • 4,917
22 votes
6 answers
5k views

What caused the downfall of Pascal? [closed]

From 1985 to 1990 Borland's Turbo Pascal was at least as popular as C for DOS systems. Turbo Pascal was especially popular because of it's ground breaking BGI graphics interface while C was stalled in ...
jwzumwalt's user avatar
  • 4,479
22 votes
5 answers
2k views

PDP-11 instruction set inconsistencies

The wiki page PDP-11 architecture has a cryptic paragraph with no references or examples: Inconsistent instructions Over the life of the PDP-11, subtle differences arose in the implementation of ...
Leo B.'s user avatar
  • 19.4k
22 votes
1 answer
5k views

Why did Windows pick 260 characters as the maximum path length?

I just got burned by the 260 character path limitation in Windows. Why did Microsoft decided to limit paths to 3 characters for drive + 256 characters + 1 character for the terminator? Mac OS of the ...
Michael Shopsin's user avatar
22 votes
2 answers
23k views

What are the differences between the Japanese Famicom and American NES?

In Japan, Nintendo's first home console was sold as the Family Computer (Famicom), while in the US it was later sold as the Nintendo Entertainment System (NES). Other than the region lock out for ...
wcarhart's user avatar
  • 919
22 votes
3 answers
3k views

Why did MS-DOS choose the percent symbol to designate variables?

I couldn't find anything but is there any reason for choosing % over $ like in *nix shells?
phuclv's user avatar
  • 3,602
22 votes
4 answers
5k views

How was digital sound playback achieved on the Commodore 64?

The Commodore 64 did not have any hardware dedicated to digital audio playback, so how were some games and songs able to achieve this on an unmodified and unextended Commodore 64? Did these ...
rcntxtlztn's user avatar
  • 2,217
21 votes
9 answers
7k views

Intel 8080-based home computers

I'd like to build an FPGA replica of a home computer based on the Intel 8080. I am not looking to design my own computer, since I would like to tap into an existing software base. Were there any ...
Cactus's user avatar
  • 2,750
21 votes
4 answers
2k views

Obscure uses of the Commodore 8050/1541 disk drive

When I was working for a foundry consultancy, we did the following Download routines to add delays when writing certain tracks. This was a security feature. When the program started, it would try ...
cup's user avatar
  • 2,517
21 votes
3 answers
4k views

Could a single NES ROM cartridge run on both PAL and NTSC systems?

Most ROMs are labeled with "(Europe)" or "(USA)", meaning PAL or NTSC. However, some are labeled "(World)". At first, I didn't think twice about this, just assuming that ...
Preston's user avatar
  • 221
21 votes
3 answers
7k views

Native C compiler for Sinclair ZX Spectrum

I am looking for a native C compiler for the Spectrum 128. I would like one which: Has good support for the latest C standard at the time. Is not limited to compiling ridiculously short source code. ...
forest's user avatar
  • 2,029
20 votes
5 answers
3k views

Size of the PDP-8

What is the physical size of a PDP-8? The photographs I found seem to be evenly divided between showing it as a compact unit that looks maybe one foot high, and as a tall cabinet maybe five or six ...
rwallace's user avatar
  • 62.4k
20 votes
6 answers
13k views

How much data could a home computer store on an audio cassette?

The use of audio cassettes for storing data for home computers was a great example of repurposing an existing invention. Cassettes were sold in a variety of capacities, and labelled with their audio ...
Kaz's user avatar
  • 8,166
20 votes
2 answers
3k views

How to check the C64 graphics mode used by Maniac Mansion

I have been investigating the MS-DOS port of the C64's Maniac Mansion game. The original MS-DOS port used the C64-specific character map to draw the various backgrounds in the game. I noticed that ...
user avatar
20 votes
5 answers
4k views

Why does the Z80 have a half-carry bit?

The Z80 apparently had a 4-bit ALU, and computes 8-bit values in two stages. The half-carry bit preserves the carry from bits 3 to 4. Why did the designers of this chip choose to preserve that value ...
Omar and Lorraine's user avatar
20 votes
9 answers
10k views

Can modern AI be used to program impressive graphics effects on very low performance home-retrocomputers, in particular 'A 3D-rotating-cube'

Can modern AI be used to program impressive graphics effects on very low performance home-retrocomputers, in particular 'A 3D-rotating-cube', effects that would be too difficult for a human to ...
texttext's user avatar
  • 379
20 votes
3 answers
5k views

Did Cray computers use virtual memory?

I found a mention on page 777 of the Second Edition of the book "Computer Systems: a programmer's perspective" [Bryant - O'Hallaron] stating that Cray supercomputers still do not use virtual memory (...
nbloqs's user avatar
  • 539

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