Questions tagged [ibm-pc]
For questions about the early IBM PC, clones and compatible systems.
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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, ...
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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 ...
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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 ...
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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 ...
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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, ...
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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,...
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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 ...
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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-...
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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,...
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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 ...
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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/...
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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 ...
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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 ...
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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 "...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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,...
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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 (...
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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 ...
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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 ...
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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 ...
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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 ...
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Meaning of KP_Begin and VK_CLEAR names of numpad 5
The key "5" at the standard keyboard numpad ("keypad" in XFree86) is named KP_Begin in XFree86 and VK_CLEAR in Windows virtual key space. What are these names originated in? Are ...
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Was there any software on the IBM PC that specifically took advantage of the NEC V20?
Back in the day I remember friends upgrading their IBM PCs (and compatibles) with a NEC V20 CPU. While this was mostly to get a bit more performance out of their machines over the stock Intel chip, I ...
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Cost of PC vs. Amiga 500 in Europe
Based on Commodore sales figures, and other historical claims, the Amiga achieved its peak popularity in 1990-91, with European sales being the leader. By 1990, with the rapid fall in PC clone prices, ...
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What was the first PC-compatible computer to have a DRAM controller?
The original IBM PC used a timer from the 8254 PIT and a channel from the 8237 DMAC in order to refresh RAM with dummy reads (and I think used NMI to signal parity errors.) I'd like to know when PC's ...
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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 ...
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Did John Carmack really invent "Adaptive Tile Refresh"?
John Carmack is credited with making fast-paced arcade games like Commander Keen possible on an IBM-PC that had no specialized graphics controllers suited for those, thanks to the "Adaptive Tile ...
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What old LCD monitor am I thinking about?
I once had a PC with an LCD monitor and I'd like to remember what model that monitor was. Here's what I remember:
It was basically a beige rectangular box with right angles on all corners. Only the ...
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