Questions tagged [ibm-pc]

For questions about the early IBM PC, clones and compatible systems.

Filter by
Sorted by
Tagged with
10 votes
5 answers
6k views

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

The PC architecture, from the original IBM PC onward, has always been designed around the idea that video memory will be on an expansion card. This was an unusual design decision; most 80s computers ...
rwallace's user avatar
  • 61.1k
17 votes
6 answers
13k views

Why didn't PC games eschew MS-DOS and deal with BIOS directly?

Given the memory referencing limits of MS-DOS for compatibility purposes, why didn't games produced for the 286+ processors eschew MS-DOS and talk directly with the BIOS or IO hardware, instead of all ...
Chorlton2080's user avatar
21 votes
5 answers
4k views

How can I reverse-engineer the game Wizardry (1981) for PC, based on UCSD Pascal?

I am looking at the files included with the 1981 game Wizardry. The particular version I have is from a 1998 re-release, but I do not know if the binary is still the original 1981 release. My ...
typedeaf's user avatar
  • 313
9 votes
0 answers
233 views

Were there Any Applications Making Explicit Use of the MDA's Colour Capabilities?

The first series of MDA adaptors for the IBM PC had the ability to show colours according to the attribute byte, much like the CGA does in text mode, but I don't remember any PC application that ...
Raffzahn's user avatar
  • 223k
3 votes
1 answer
345 views

Questions about IBM PC PSU P8 key pin and change to +5V for AT

According to the IBM PC/XT Technical Reference page 3-6, pin 2 of plug P8 is a "key." (Note that this is the pin specifically; this is separate from the keying of the shroud, which is ...
cjs's user avatar
  • 26.1k
7 votes
3 answers
1k views

Were there any PCs where you could switch Turbo Mode via the keyboard?

All the PCs I have personally used or encountered which had a "Turbo Mode" (clock frequency switch, with frequencies in the 5-25MHz range) did this via a hardware button similar to the reset ...
dirkt's user avatar
  • 27.3k
7 votes
1 answer
463 views

How to treat an old PC

I have an old IBM PS/2 30/286, now sitting for a while on one of my desks. I'm a bit afraid that it will stop working sooner or later, so what's the best way to keep it 'alive' ? I fire it up every ...
Tommylee2k's user avatar
7 votes
2 answers
561 views

Were VGA palette's HSV math properties used in practice?

In "Why were those colors chosen to be the default palette for 256-color VGA?", we've established that 216 of its colors represent a 24x3x3 truncated HSV color space. This results in an ...
Therac's user avatar
  • 753
8 votes
1 answer
377 views

Why weren't CGA colors selectable from palette?

Most memorable graphics mode in games for CGA was 320x200 which supported 4 colors. (I know there was 16 color composite mode trick, but let's ignore that.) Those 4 colors could be selected from ...
user694733's user avatar
37 votes
4 answers
8k views

Why were those colors chosen to be the default palette for 256-color VGA?

Although subjective, I believe I'm not the only one considering default VGA 256 color palette to be hideous and ugly. What is the story behind this, why were these particular colors chosen?
tuomas's user avatar
  • 2,803
7 votes
5 answers
2k views

Was there a notable mainstream 640×480 monochrome display for PC earlier than MCGA

On IBM PC compatibles, the first widely-known display subsystems capable of displaying 640×480 pixels (resulting in square pixels with a 4:3 display) were the MCGA and VGA in 1987. By then, 640×400 ...
airman's user avatar
  • 1,350
6 votes
1 answer
535 views

Have I Screwed the CMOS by Booting With the Clear Jumper Set?

I've been playing around with one of my old PCs recently, an IBM PC 340, and at some stage in trying to get a compact flash adapter to play nice I hit a weird issue where the system BIOS (a Surepath ...
Matt Lacey's user avatar
  • 2,212
13 votes
4 answers
4k views

What actions, besides a hard power-off, did a blank screen with a blinking cursor allow?

I remember that, in the old days, a serious boot error could manifest in a screen like the above. (I have no idea if this may still happen. I haven't seen it for years, so I assume it is legacy as of ...
gaazkam's user avatar
  • 239
6 votes
6 answers
2k views

When was the end of the floppy-only IBM PC clone?

Can we pinpoint in what year the number of IBM-compatible PCs (whether original IBM machines or clones) sold without a hard disk drive became so negligible that almost all new commercial software, ...
TeaRex's user avatar
  • 703
4 votes
1 answer
529 views

How do you find the EBDA address?

Normally, the "Extended BIOS Data Area" (EBDA) is located at the segment stored at 0x0040:0x000E, but this is only true for EISA and MCA systems (at least that's what I found in various ...
DarkAtom's user avatar
  • 2,337
5 votes
1 answer
306 views

Documentation for the SALUT preprocessor of the IBM Macro Assembler 2.0

The IBM Macro Assembler 2.0 included the SALUT program, which was a preprocessor for assembly language for structured programming. It was also included in the IBM Macro Assembler/2. I am looking for ...
Marc Nieper-Wißkirchen's user avatar
23 votes
2 answers
4k views

Were there any PCs using the i376?

The Intel 80376 was an x86 CPU that didn't support Real Mode or paging. It was targeted for embedded applications and it wasn't very successful at that (the 80386EX overtook it). Under these ...
DarkAtom's user avatar
  • 2,337
8 votes
1 answer
564 views

Can you name this 386/486 era computer case?

Escort Computer is a Local PC brand in Turkey. They had popular Escort Multimedia series in late 90's. Prominent with distinctive case design. They were using off the shelf OEM hardware. I believe, ...
wizofwor's user avatar
  • 2,788
9 votes
4 answers
2k views

Detecting if a video mode is supported by INT 0x10

The PC BIOS uses the INT 0x10, AH=0x00 function to change the video mode. There's a big list of video modes available, but how can I be sure that the video mode I want to set is supported? For example,...
DarkAtom's user avatar
  • 2,337
6 votes
1 answer
624 views

AMD Interwave audio fx

I hope it's retro enough. Does anyone have any info on how AMD Interwave did sound effects? I'm mostly interested in reverb, but others would be nice to know about as well. The question is ...
Anton's user avatar
  • 477
12 votes
2 answers
1k views

Floppy drive detection on an IBM PC 5150 by PC/MS-DOS

The only functions of INT 13h available for pre-XT systems are the first six, from AH=00 to AH=05 (see here and here) Since function AH=08 (Get current drive parameters) is unavailable, how does PC-...
padawan's user avatar
  • 447
4 votes
1 answer
521 views

How to use thinkpad x230 with PCjr 4863 monitor?

I understand it is probably more trouble than it is worth, but I am keen on using my 4863 IBM monitor as a second display for my x230. So far I've looked into converting its VGA signal to a CGA output,...
jayVeni's user avatar
  • 41
18 votes
5 answers
3k views

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

AFAIK VGA mode 13h palette has only 64 possible colors (6-bit) per channel. One obvious way to map those 64 colors to 256 colors is to multiply them by 4 (since 4 * 64 = 256): 8_bit = 6_bit * 4; This ...
tigrou's user avatar
  • 365
14 votes
1 answer
2k views

Beep command with letters for notes (IBM AT + DOS circa 1984)

I'm looking for a reference for a command which used letters for musical notes, and would play very simple tunes with square waves. It ran on an IBM AT, circa 1984, which was running a version of IBM/...
jonathanjo's user avatar
16 votes
4 answers
2k views

Is it possible to detect a CGA card on an IBM PC 5150 by write/reading the Motorola 6845?

I am trying to programatically detect the CGA card on old IBM 5150-ish PCs. The Paku Paku game source code doesn't directly detect it. The strategy is to detect VGA, EGA, Tandy, PCJr, etc etc, then if ...
don bright's user avatar
24 votes
16 answers
5k views

What were the most popular text editors for MS-DOS in the 1980s? [closed]

Since versions 1-5 of MS-DOS only came with the Edlin line-based editor, but were released on the IBM PC and compatibles, which had screen-based user I/O, my feeling is that most users wouldn't have ...
Brian Reading's user avatar
14 votes
3 answers
2k views

Help porting nasm code down from 386 to 8088 (shifts by more than 1 bit)

I have been writing some small asm COM program using Netwide Assembler (nasm), but am having trouble getting it to run on 8088 emulators like PCjs. I could use some help translating the assembly "...
don bright's user avatar
26 votes
3 answers
4k views

What did Ctrl+NumLock do?

In my answer here I infer that the unusual scancode for the Pause/Break key emulates the user pressing and then releasing CtrlNumLock. Obviously that key combination did something specific, back when ...
user253751's user avatar
4 votes
3 answers
359 views

Were there clones and/or national variants of IBM's 84-key AT keyboard?

The 84-Key IBM AT keyboard (the one with a visibly separated numbers block but without dedicated cursor keys, with ESC and a dedicated SysRq key in the numbers block) seems to be the rarest of the old ...
TeaRex's user avatar
  • 703
14 votes
3 answers
5k views

Which font with slashed zero is being used in this screengrab?

Do you know which font is being used in the video here: https://www.youtube.com/watch?v=xnudvJbAgI0? A screengrab of the video that shows a lot of text: We can see that the zeros are slashed, so it ...
Lone Learner's user avatar
7 votes
2 answers
349 views

Why did some BIOSes have the timer tick wrap around at 1800B1h instead of at 1800B0h?

The 1989 2nd edition of the DOS PROGRAMMER'S REFERENCE says: Midnight is determined as the number of ticks in a complete day of 86400 seconds (1573040 ticks of the clock, for a total elapsed time of ...
Sep Roland's user avatar
  • 1,053
14 votes
1 answer
979 views

What technical aspects make NEC PC-98 architecture incompatible with IBM PC architecture?

PC-98 was a series of x86-based Japanese computers that offers Kana-Kanji support, which shared some hardware similarities and operation systems with IBM PC, and software was relatively easy to port ...
Schezuk's user avatar
  • 3,752
23 votes
6 answers
6k views

Were CD-ROM-based games able to "hide" audio tracks inside the "data track"?

I have been digitizing the audio tracks from various old CDs lately, because I have become a lossless audio snob who no longer is able to tolerate MP3s but need FLACs of everything. Many of these are ...
Dauson S.'s user avatar
  • 231
28 votes
8 answers
7k views

Why did x86 support self-modifying code in the 80s and 90s?

In this question, by 'self-modifying code', I mean software that writes to a section of code that the CPU will very soon fetch and attempt to execute. I am not here talking about the software ...
rwallace's user avatar
  • 61.1k
10 votes
3 answers
2k views

How to write text in MODE 0x13?

I have read How to write directly to video memory using "debug.exe" in MS-DOS? and I know how to write text to video memory in mode 0x3 but I can't figure out how to write text to video ...
Lone Learner's user avatar
23 votes
6 answers
9k views

Why was video, audio and picture compression the poorest when storage space was the costliest?

"Full-motion video" sequences in PC and console games in the 1990s were bad-looking, in spite of taking huge amounts of storage space. Same thing with random short video clips that I ...
Romalis's user avatar
  • 281
19 votes
8 answers
7k views

Why did IBM PC have horizontal cursor instead of vertical or block cursor?

Most 8 bit machines, like C-64, seem to have block cursors, while modern user interfaces often have vertical cursors. PC has horizontal cursor of two (or 3) scanlines by default, and block cursor for ...
tuomas's user avatar
  • 2,803
22 votes
4 answers
3k views

Was it possible to cause persistent changes to a mid-1980s IBM-PC using POKE in GWBASIC?

TL;DR: Using the DEF SEG and POKE commands in GWBASIC, was there any way to make changes to an IBM-PC compatible computer that would (a) persist even after a reboot and (b) cause an increase in crash ...
Schmuddi's user avatar
  • 925
18 votes
3 answers
2k views

IBM PC Alt + numpad for entering character codes: firmware, BIOS or OS?

Back in the days of MS-DOS, when I needed to type a special character that wasn't part of the keyboard layout, I would press down the left Alt key and type out the character code on the numeric keypad ...
Nimloth's user avatar
  • 2,068
24 votes
2 answers
4k views

How did Joysticks with more than 4 buttons and all those extra features work on a Game Port?

The question is pretty straight forward. How did they do so much more than the simple, unidirectional 4 axis of analog control, plus 4 on/off buttons? There was surprisingly precise force feedback ...
nabeelr's user avatar
  • 341
13 votes
1 answer
4k views

What is this early 3D platformer?

Video: https://www.youtube.com/watch?v=8_-fcFivTS8&t=599s Image: I'm having a hard time tracking down a game I played when I was a kid. It was on DOS in the early 90s. It had flat-shaded polygon ...
mm201's user avatar
  • 245
5 votes
5 answers
514 views

Chaining IRQs in x86 ROM code

Objective Summary: I need to write a sleep() function to be used in 8088 (PC/XT ISA) ROM code with 1 ms resolution. Though the question can be more generalized to chaining INTs with data in different ...
640KB's user avatar
  • 1,297
39 votes
4 answers
7k views

Why does NumLock exist?

My keyboard has over a hundred keys on it. But there's one labelled NumLock. Pressing it turns the numeric keypad into a duplicate of the dedicated arrow keys just left of it. This doesn't seem useful ...
MathematicalOrchid's user avatar
23 votes
2 answers
4k views

What is a "sympathetic bit"?

I am reading about BIOS in Phil Storrs PC Hardware book: What happens when we turn on a PC ? Next comes the incremental check of all the RAM memory. The RAM memory is written to, and read from, with ...
Flux's user avatar
  • 541
23 votes
3 answers
4k views

How does the BIOS distinguish Interrupt(08h-12h) from INT instructions, vs. actual exceptions inside the CPU?

This is purely academic, out of date, out of curiosity. Let's go back to the 1990s, before Windows, when real-mode DOS programs were common. The BIOS assigned INT 08H+ for their own interrupt handlers,...
THS's user avatar
  • 333
4 votes
1 answer
282 views

IBM/Xebec XT Fixed Disk Adapter "Custom" Drive Types

It's generally believed that the IBM/Xebec Fixed Disk adapters were hardware limited to only four different drive geometries - of which, only the last revision of the card was user configurable (...
640KB's user avatar
  • 1,297
9 votes
2 answers
2k views

How to determine BIOS-provided (INT 13h) hard disk geometry, and how to fix the MBR partition table to agree with it?

When transferring a hard drive from one computer to another, sometimes a situation can occur where the BIOS-provided CHS hard disk geometry (interrupt 13h without extensions) is different from the CHS ...
Alex Cannon's user avatar
15 votes
2 answers
2k views

What information was "off limits" to IBM PC clone BIOS authors?

Back in the PC clone days the accepted legally defensible method of selling a non-IBM PC BIOS was using a "clean room" whereby an engineer who had never been exposed to proprietary IBM ...
640KB's user avatar
  • 1,297
32 votes
7 answers
5k views

Did any PC software floating point use non-IEEE format?

During the 1980s, prior to the 486 (well, strictly speaking, prior to the discontinuing of the 486SX in the nineties), IBM PCs and compatibles had hardware floating point only in the form of an ...
rwallace's user avatar
  • 61.1k
5 votes
1 answer
674 views

Who were the market for those "speed up your computer" shareware applications back in the day? [closed]

In the Swedish computer magazine PC Hemma ("Home PC") from February 1997 (p. 68), they included a floppy disk with shareware programs related to "trimming your PC", as well as a ...
Tarlton's user avatar
  • 67

1
2 3 4 5 6