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96 votes
11 answers
14k views

What key factor led to the sudden commercial success of MS Windows with v3.0?

Microsoft Windows was originally introduced in 1985, ostensibly to compete with the Apple Macintosh, and other computers shipping with graphical shells by that time. However, early versions of Windows ...
Brian H's user avatar
  • 60.8k
63 votes
3 answers
7k views

How does the LOADALL instruction on the 80286 work?

This undocumented instruction existed in the 80286 and, I believe, the 80386. I think it was added while debugging the chip, so the engineers could quickly put the processor into any state and test it ...
mcleod_ideafix's user avatar
62 votes
3 answers
17k views

Who set the 640K limit?

We all know that "640K should be enough for everyone". But who actually set this limit? The quote is often attributed to Bill Gates, but it doesn't seem like a decision for an Operating System vendor ...
PkP's user avatar
  • 959
29 votes
2 answers
4k views

How did an IBM 5150 with 16KB RAM work?

I keep reading that when it was first released, there was a variant of the IBM PC model 5150 that had only 16KB of RAM installed. From a hardware perspective, this would clearly work - the 5150 ...
Jules's user avatar
  • 13k
110 votes
10 answers
44k views

Why do C to Z80 compilers produce poor code?

When reading some other questions about compiling C for the Z80, How much benefit should be expected on a more advanced compiler for z80/r800 based computers? Native C compiler for Sinclair ZX ...
Omar and Lorraine's user avatar
59 votes
9 answers
14k views

What was the rationale behind 36 bit computer architectures?

Was there some particular design theory or constraint that made a 36 bit word size attractive for early computers? As opposed to the various power-of-2 word sizes which seem to have won out?
Mark Harrison's user avatar
36 votes
3 answers
14k views

What modification is required from a PC floppy for use in Amiga?

Around the end of the time of Amiga popularity, obtaining a replacement Amiga floppy drive was a nuisance, while PC drives were ubiquitous and cheap. One could install a PC drive in Amiga after ...
SF.'s user avatar
  • 7,105
33 votes
6 answers
32k views

Windows 98 with 2GB of RAM

I have assembled a retro-gaming PC out of an old Shuttle SN45G with a Windows 98/Windows XP dual boot. The motherboard can handle 2GB of RAM, but apparently Windows 98 can only handle 1 GiB. Windows ...
Informancien's user avatar
  • 2,657
25 votes
4 answers
6k views

Z8410 DMA chip as GPU?

There are basically two ways to design a 2D graphics system: Provide lots of hardware support in the form of tiles, hardware scrolling and sprites, to put together each frame on the fly from a small ...
rwallace's user avatar
  • 61.4k
88 votes
9 answers
16k views

Why is the processor instruction called "move", not "copy"?

Many processors have an instruction called "move" (sometimes spelled MOV) which copies data from one location (the "source") to another (the "destination") in registers and/or memory. It does not do ...
JoelFan's user avatar
  • 2,127
45 votes
4 answers
42k views

Commodore 64 to modern TV

I've been thinking about getting a Commodore 64 machine. However, I realise there's obviously no video cables I have that will work. But when I looked online there are many people using S-Video to VGA ...
crabcrabcam's user avatar
34 votes
4 answers
17k views

What exactly is a cycle-accurate emulator?

Emulators such as Higan are cycle-accurate and thus have full compatibility with all existing software. In a 2011 Ars Technica article, much was said about cycle accuracy and how it preserves games by ...
Matheus Moreira's user avatar
33 votes
3 answers
5k views

Reconditioning and cleaning old Nintendo (and other) game cartridges

I used to blow the dust out of the cartridges but I heard that can actually damage the cartridge or the system itself. I am looking for the proper way to clean old Nintendo game cartridges (such as ...
Tim Penner's user avatar
33 votes
1 answer
4k views

How does the command.com shell work with MS-DOS?

On my systems that are running MS-DOS, I change the default command.com to 4DOS for more features. How was the shell system designed and how did it with the operating system in MS-DOS that it enabled ...
Thraka's user avatar
  • 2,913
26 votes
5 answers
4k views

Why is the RM Nimbus PC-186 not IBM PC compatible?

The RM Nimbus range of computers were popular in British schools during the late 80s and into the 90s. When I was at high school Nimbus PC-186 machines were all over the place. Many web pages that ...
Richard Downer's user avatar
18 votes
5 answers
4k views

What tools were used in late MS-DOS era for reverse engineering and patching binary executables?

In the late MS-DOS era, what were the state of the art software tools for reverse engineering and patching binaries, i.e. .exe and .com files? A simple list of the tools that were "state of the art", ...
AlphaCentauri's user avatar
15 votes
6 answers
8k views

How can I adapt a digital CGA/C128 signal (RGBI DE-9) to a modern monitor?

IBM's CGA and the Commodore 128's RGB video output both use a DE-9 connector. How do I adapt the CGA video output from an IBM XT 5160 or Commodore 128 to a modern monitor?
snips-n-snails's user avatar
11 votes
4 answers
12k views

How do I create a boot menu to select between Windows and DOS?

I was not a PC user before Windows 98. But I remember one of my friends was using a boot menu in his 486 machine to select between Windows/DOS. The menu was like: 1. EMS 2. XMS 3. Windows If we ...
wizofwor's user avatar
  • 2,778
147 votes
5 answers
53k views

It's now safe to turn off your computer

One thing I remember very well from my childhood is the screen you got at the end of a shutdown process on old computers: I don't know if this was a Windows 95/98/2000/ME only thing but I wonder why ...
arminb's user avatar
  • 1,351
99 votes
1 answer
30k views

Why did MS-DOS applications built using Turbo Pascal fail to start with a division by zero error on faster systems?

On faster MS-DOS systems, it wasn't entirely uncommon for applications built using Borland's Turbo Pascal to fail to start, and (before exiting back to the command prompt) to report a division by zero ...
user's user avatar
  • 5,296
74 votes
8 answers
24k views

Which Linux or BSD distributions do still support i386, i486 or i586 CPUs?

Unfortunately Debian kicked out Pentium 1 (i586) CPU support from its 32-bit PC port (named i386 for historic circumstances) for its next stable release Debian 9 Stretch. (Then again they complain ...
Axel Beckert's user avatar
20 votes
8 answers
2k views

Retrocomputing software development process/methodologies

This is a test question based on this meta post. If the question can be reworded to be more on-topic, please feel free to suggest improvements. This is an open ended question about software ...
JAL's user avatar
  • 9,520
18 votes
1 answer
3k views

Which undocumented 8085 instructions is Steven Morse referring to in "In The Beginning"?

In S. P. Morse's 1980 allegory, "In The Beginning", he writes And Intel said, "Let there be an 8085 with an oscillator on the same chip as the processor, and let an on-chip system controller ...
Evan Carroll's user avatar
  • 3,388
17 votes
2 answers
7k views

Is the Game Boy Sharp LR35902 object-compatible with the 8080/Z-80?

(Note: by "object-compatible" I mean that the opcodes and their following operands are the same—the assembler produces the same output for equivalant assembler mnemonics. This of course ...
cjs's user avatar
  • 26.6k
17 votes
1 answer
1k views

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 ...
Raffzahn's user avatar
  • 224k
14 votes
3 answers
2k views

What format is the (Timex) Sinclair ZX Spectrum SCREEN$/.SCR file

What format is the (Timex) Sinclair ZX Spectrum SCREEN$/.SCR file and how is the fore/background and attribute data encoded within this format?
John Parker's user avatar
8 votes
1 answer
992 views

What's the difference between Kansas City tape standard and CUTS?

A number of a different computer systems use a tape encoding based on either the Kansas City or CUTS standards. There's a very brief overview on Wikipedia, but it's not clear what the difference ...
Jules's user avatar
  • 13k
148 votes
6 answers
21k views

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

Cellphone / Telephone have the seven bottom-left and the one top-left. While the keyboard has the seven top-left and the one bottom-left How did this come to be? Is there an interesting computing ...
Neil Meyer's user avatar
  • 6,497
85 votes
11 answers
29k views

How were the first ZX Spectrum games written?

Being a child of the 80s I loved my ZX Spectrum, did my best to learn BASIC but I felt like the games I was playing (Jetpac, Dizzy, Renegade etc) were perhaps not written using BASIC. I wondered: how ...
Remy Sharp's user avatar
  • 1,097
80 votes
14 answers
19k views

Back in the late 1980s, how was commercial software for 8-bit home computers developed?

When hobbyists wanted to write software for e.g. the Commodore 64, they either used the built-in BASIC interpreter (with all its limitations) or some native tools, like compilers for other languages ...
Felix Palmen's user avatar
  • 1,492
55 votes
8 answers
11k views

Why didn't the 8086 use linear addressing?

The 8086 used a segmented memory architecture where the linear address was computed from a 16-bit segment number and a 16-bit offset. This greatly complicated things from a programming perspective. ...
Alex Hajnal's user avatar
  • 9,350
55 votes
9 answers
26k views

How long will floppy disks maintain data integrity?

This was on CNN today: The U.S. is still using floppy disks to run its nuclear program Which led me to read through this article: Think the floppy disk is dead? Think again! Here’s why it still ...
Aaron's user avatar
  • 2,384
51 votes
4 answers
5k views

What precautions to take when powering on old computer for the first time in years

I have a Commodore 128D that hasn't been powered in about 15 years. I want to begin using it again. It has been stored in cool dry places like attached garages, in a cardboard box. I hope this ...
nexus_2006's user avatar
  • 1,065
50 votes
5 answers
17k views

Why did CPU designers in the 70s prioritize reducing pin count?

A lot of 70s era microprocessors were packaged in DIP packages with 40 pins. This was a reasonably good fit for 8-bit processors: 16 address lines, 8 data lines, 2 power and clock are all absolutely ...
Jules's user avatar
  • 13k
45 votes
3 answers
4k views

Why are the symbols on the number keys of PC & Mac keyboards different to ASCII keyboards?

On a US-layout PC keyboard, the symbols above the number keys are as follows: Whereas the keyboard on an Apple II is different: Note, for example, the '(' and ')' symbols are now above 8 and 9, and '...
Kaz's user avatar
  • 8,146
44 votes
4 answers
15k views

Why did 80x25 become the text monitor standard?

Prior to the 1981 release of the IBM PC, the VT05 (72x20 1970), VT50 (80x12 1974), VT52 (80x24 1975), and VT100 (80x24 1978) text terminals were used on many Unix machines and the PDP-11 (probably the ...
Barnstormer's user avatar
  • 1,359
34 votes
9 answers
41k views

How can you connect an Amiga 500/600/1000/2000 to a modern monitor?

I have an Amiga 500 that I'd like to get up and running again, but the 1084 monitor with which I used to use it has flyback transformer issues. What options are available to hook it up to a modern ...
Jim MacKenzie's user avatar
28 votes
2 answers
9k views

The start of x86: Intel 8080 vs Intel 8086?

Why is it said that all modern Intel processors of the x86 family are said to descend from the Intel 8086 and not the Intel 8080? From the Wikipedia article on the Intel 8086, The 8086 gave rise to ...
Evan Carroll's user avatar
  • 3,388
23 votes
1 answer
4k views

How did large .COM files work?

An MS-DOS .com file is just raw code/data without header, thus no linking information, and was limited to be loaded into just one segment (64kB). That's the reason corrupted binaries would print "...
DarkDust's user avatar
  • 1,488
22 votes
3 answers
3k views

What makes slot 7 of the Apple ][ unique from 1-6 and how was this used?

In the Apple II, there are three unique slots (depending on model): Slot 0 (on the ][ / ][+) which is typically used for language cards. "Aux" slots in the //e and IIgs, typically used for memory ...
bjb's user avatar
  • 16.4k
20 votes
1 answer
2k views

Apple IIgs: Hardware implementation of RAM shadowing

On the Apple IIgs, the 256K of built-in main memory is divided into two sections: The "fast" RAM, banks 00 and 01, and the "slow" RAM, banks E0 and E1. CPU access to slow RAM required the CPU to slow ...
fluffysheap's user avatar
18 votes
3 answers
3k views

Why does Sinclair BASIC have two formats for storing numbers in the same structure?

The ZX Spectrum has two formats for storing numbers, both 40 bits, or five bytes. The first is a floating point format, which consists of one exponent byte, and four mantissa bytes. The first bit of ...
Omar and Lorraine's user avatar
17 votes
8 answers
8k views

Why was the DOS kernel discarded?

I've read that the last DOS kernel based Windows was ME. Later versions use the NT kernel. Why did Microsoft rewrite the whole kernel? Why was the DOS kernel discarded?
zomega's user avatar
  • 5,372
17 votes
1 answer
2k views

Can you use 5.25 HD floppy disks in a DD drive?

Is is possible to format and use 5.25 high density disks in a double density drive?
Matthew's user avatar
  • 173
16 votes
3 answers
3k views

Finding byte boundaries in floppy disk MFM bitstreams

I'm building myself a floppy disk interface based on a microcontroller. I'm successfully reading the bitstream off the disk and (probably) decoding the MFM bitstream into actual bits, based on the ...
David Given's user avatar
  • 1,320
16 votes
4 answers
3k views

Did the Intel 8086/8088 not guarantee the value of SS:SP immediately after RESET?

I'm poking at the Intel 8086/8088 (iAPX 86/88) User's Manual, which states on page 2-29 (PDF page 48), table 2-4, CPU State Following RESET, that the state of the CPU after the RESET pin rising ...
user's user avatar
  • 5,296
14 votes
1 answer
790 views

Why does Applesoft BASIC get confused by a nonzero value at $0800?

Applesoft BASIC programs start at location $0801 in memory (usually). If you put a nonzero value at address $0800, though, you get an error when you try to run the program: ?SYNTAX ERROR IN 65124 ...
fadden's user avatar
  • 9,050
11 votes
3 answers
1k views

Where can I donate my old Computer Shopper Magazines to make sure they get scanned and shared?

I am sure many of you remember the gigantic Computer Shopper magazines of the 1990's; but Computer Shopper actually dates back to sometime in 1979, and still exists in electronic form today. In my ...
Geo...'s user avatar
  • 10.2k
9 votes
2 answers
1k views

74'181 ALU why would anyone (have) use(d) these wild functions? [closed]

Got myself a bunch of 74LS181, because they were cheap and they have been used in the VAX 11/780. And now I made myself a little tester breadboard where I am trying to figure this out in practice. My ...
Gunther Schadow's user avatar
4 votes
3 answers
4k views

Reading both keyboard and joystick with non-KERNAL code on C64

I'm implementing non-KERNAL joystick and keyboard controls for my Commodore 64 game. I used to use the KERNAL SCNKEY routine earlier to read keyboard and it worked well with my joystick port 2 code. ...
Nurpax's user avatar
  • 495

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