Questions tagged [ibm-pc]
For questions about the early IBM PC, clones and compatible systems.
248
questions
63
votes
7
answers
18k
views
What did the 'turbo' button actually do?
I remember the computer I played Commander Keen on as a child had a turbo button that I was forbidden to touch, what did this button actually do?
- 34.7k
36
votes
4
answers
7k
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?
- 28.3k
7
votes
2
answers
520
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 ...
- 237
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 ...
8
votes
1
answer
289
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 ...
- 213k
32
votes
5
answers
5k
views
Does every retrocomputer and console with NTSC composite output have 'artifact color' ability?
Artifact color is heavily associated with the Apple ][, since that is the only method the machine had to produce a color display. I was looking at the fantastic demo for IBM PC + CGA, 8088MPH, and I ...
- 34.7k
6
votes
1
answer
510
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 ...
- 2,144
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 ...
- 303
8
votes
4
answers
763
views
Who produced all-in-one / wedge style IBM compatibles?
The RetroManCave YouTube channel recently made me aware of the Sinclair PC-200 / Amstrad PC-20 and I already knew about the Tandy 1000EX / 1000HX but were there any other IBM-compatibles (or mostly ...
- 21
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 ...
- 3,505
15
votes
3
answers
3k
views
Who were the first engineers to "cleanroom" the IBM PC BIOS?
In the first season of the AMC show Halt & Catch Fire, the protagonist "Cameron Howe" is introduced.
Cameron portrays a rookie engineer who is recruited for being extraordinarily talented, and is ...
4
votes
1
answer
227
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 ...
- 213k
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, ...
- 3,505
4
votes
1
answer
483
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 ...
- 12.4k
22
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 ...
- 118k
8
votes
0
answers
393
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, ...
- 2,728
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,...
- 33k
6
votes
1
answer
616
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 ...
- 3,505
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-...
- 3,505
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 ...
- 1,043
4
votes
1
answer
513
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,...
- 26.1k
24
votes
6
answers
34k
views
How to use ISA card in modern PC
(Posted this on HW Rec but got no responses.)
Would like to use an ISA expansion card in a modern PC. There are
Expensive PCI - ISA adapters (but I cannot find any actually for sale now)
USB-ISA ...
- 118k
4
votes
3
answers
351
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 ...
- 2,012
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/...
- 118k
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 ...
- 1,626
21
votes
4
answers
2k
views
Did the IBM PC use the 8088's NMI line?
As I understand it, the Intel 8088 CPU used in the original IBM PC had two interrupt lines: INTR and NMI. INTR was fed from the Intel 8259 Programmable Interrupt Controller, which handled the IRQs ...
- 36k
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 ...
- 8,549
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 "...
- 21.6k
18
votes
7
answers
7k
views
Are there any good, non-abandoned PC emulators?
Mission: I'm trying to simulate a classic ~286/386/486/Pentium inside my modern PC (running Windows 10) in the most authentic way possible.
Just a quick note to say that I (Sarah Walker) have decided ...
- 727
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 ...
- 118k
16
votes
2
answers
880
views
What was special about "Vulcan" - the CP/M database program?
The Vulcan DBMS for CP/M micros was originally developed in 8080 assembly language by a contractor working for Jet Propulsion Lab, based on an earlier JPL mainframe program. This code went on to be ...
7
votes
2
answers
306
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 ...
- 1,043
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 ...
- 21.6k
31
votes
5
answers
5k
views
What really is a sound card driver in MS-DOS?
To my knowledge, neither MS-DOS nor BIOS offers any kind of API for sound cards. Therefore the concept of a "driver" is absent, as we know it today. Apart from accessories and sample files ...
- 118k
24
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 ...
- 1,164
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 ...
- 21.6k
7
votes
2
answers
2k
views
IBM PC memory map - why RAM at the bottom?
The 8088 provided an address space of one megabyte.
The IBM PC allocated that address space as 640K RAM (not that the 5150 could physically take that much, but the address space was allocated) ...
- 213k
13
votes
2
answers
1k
views
In what year was my old, long-lost IBM PC made and which form factor/model was it?
I've spent a ridiculous amount of time and effort over the years just trying to figure out what exact IBM product I grew up with. At last, I've finally established for 100% certain that it was a:
IBM ...
- 670
14
votes
1
answer
954
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 ...
- 28.3k
34
votes
2
answers
5k
views
How did MS-DOS assign drive letters in the case of more than two floppy disk drives?
The IBM PC BIOS had provisions for up to four floppy disk drives, by virtue of returning the number of floppy disk drives in a two-bit field plus a none/some flag (allowing for reporting values of 0, ...
- 21.6k
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 ...
- 1,951
18
votes
5
answers
6k
views
What was the first multiprocessor x86 motherboard?
I know dual socket motherboards were around in the 90's before Intel released the Core series. And SMP hardware and operating systems have been around earlier than the PC platform of course.
...
- 118k
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 ...
- 345
27
votes
5
answers
7k
views
Why was IBM BASIC so Huge?
The early versions of Microsoft BASIC required 4KB of ROM, and many versions existed in the 8KB and 16KB size. But Microsoft's IBM BASIC (known as "Cassette BASIC") for the original IBM PC (Model 5150)...
- 21.6k
9
votes
1
answer
735
views
Was sector size under software control on the original IBM PC floppy drive controller?
The original IBM PC used a 5.25" floppy disk format of two sides, 40 tracks, 9 sectors per track, 512 bytes per sector, for 360K per disk.
As I understand it, a significant amount of disk space ...
- 118k
19
votes
8
answers
6k
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 ...
- 213k
34
votes
3
answers
3k
views
Why did connecting the IBM PC 3.5" FDD backwards cause the problems it did?
When the 3.5" FDD was introduced for the IBM PC and compatibles (or possibly earlier), someone made a decision to make the data cable between the controller and drive unkeyed. This, of course, meant ...
- 171
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 ...
- 1,479
4
votes
1
answer
263
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 (...
- 1,287
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 ...
- 21.6k