Questions tagged [ibm-pc]

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

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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
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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
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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
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
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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
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59 votes
4 answers
18k views

On DOS computers, what would the PARK command do?

In 1994 or so, we had an old computer at my primary school. I remember finding out that it had a park command. From reading its documentation, it said that this command should be executed prior to ...
gerrit's user avatar
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35 votes
2 answers
6k 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, ...
user's user avatar
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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 ...
Brian H's user avatar
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19 votes
2 answers
7k views

First commercial DOS game?

What was the first commercial game sold for use on IBM/MS/PC DOS after the IBM August 12, 1981 release.
jwzumwalt's user avatar
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19 votes
3 answers
2k views

How did the IBM PC handle multiple physical devices serving memory at the same physical address?

I'm trying to figure out how the IBM 5150 PC handled the case where multiple physical devices (memory chips) were mapped to the same address within the 8088's physical address space. The closest I've ...
user's user avatar
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62 votes
7 answers
19k 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?
Neil Meyer's user avatar
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49 votes
9 answers
12k views

Why weren't bootable game disks ever common on the IBM PC?

While for other platforms of that era (primarily, Amiga), putting a game on a bootable disk was quite a normal practice, this approach never taken off on IBM PC. Why not? I do remember people having ...
DmytroL's user avatar
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48 votes
9 answers
14k views

Why did the IBM PC need a sound card?

The original IBM PC and later variants used an Intel 8253 or 8254 as a sound chip. Why did users add sound cards such as the Adlib or Sound Blaster. I remember voice output with programs like ...
jwzumwalt's user avatar
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35 votes
4 answers
7k views

What was the IBM PC cost saving for using the 8088 vs 8086?

The decision to use the 8088, a version of the 8086 with the data bus restricted to 8 bits, in the original IBM PC, seems strange on the face of it, certainly hurt performance and intuitively shouldn'...
rwallace's user avatar
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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
26 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
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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
  • 11.9k
19 votes
3 answers
4k views

How do CGA emulators for Hercules graphics work?

HGC cards on IBM PCs used to be able to run CGA software by using a CGA emulator. How exactly did those programs work? What were the limitations?
Arne's user avatar
  • 1,274
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
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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. ...
LawrenceC's user avatar
  • 1,199
16 votes
5 answers
4k views

Adding the third floppy drive?

I've seen a few computers with more than two floppy drives, most with two 3.5" and one 5.25". My question is how was this achieved? I've heard that it could be done with a second controller card, but ...
redsPL's user avatar
  • 1,017
11 votes
3 answers
6k views

Restore corroded AT motherboard with dead CMOS battery

I have acquired a nice MS-DOS PC from EET Computer (I couldn't find any information about them). It actually works, but I have two errors on boot: Floppy disk drive controller failure; CMOS Battery ...
Informancien's user avatar
  • 2,657
11 votes
1 answer
2k views

How can I edit CMOS hard drive geometry settings on a 1991 PC?

First, I am NOT asking how to use the BIOS Setup utility. I'm asking how to OVERRIDE the built-in settings my BIOS Setup supports for the HD geometry. I have a 1991 NCR PC with a 386SX, on-board IDE, ...
Brian H's user avatar
  • 60.8k
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
4 votes
1 answer
390 views

Did the IBM Game Control Adapter have I/O port aliases?

I was taking a look at the logic diagram in the manual for the original IBM game port adapter card: In the upper-left corner of the schematic, there is the circuitry responsible for decoding the I/O ...
smitelli's user avatar
  • 1,769
76 votes
8 answers
22k views

Why did IBM make the PC BIOS source code public?

IBM released the IBM 5150 Technical Reference manual in August, 1981, and included in it the fully commented source code listing for the BIOS. I find this odd for two reasons: IBM must have realized ...
Brian H's user avatar
  • 60.8k
71 votes
3 answers
6k views

Why was the return key symbol ↵ drawn differently from the motion of a CR-LF?

In the operating system (DOS) of IBM PCs, newlines were represented by a carriage return (CR) character, followed by a line feed (LF) character. The motion of a printer or teletype receiving such a ...
DrSheldon's user avatar
  • 16k
69 votes
3 answers
15k views

What character is the MS-DOS cursor?

The cursor used on my 486 (and Pentium 3) in MS-DOS 6/7 has a thick underlined character. I cannot find that in code page 437. The underscore character is the closest to it, but is thinner. Where ...
Thraka's user avatar
  • 2,913
62 votes
7 answers
10k views

Why did some old MS-DOS games lack the ability to exit them?

While playing around in DOSBox-X, I'm reminded of some DOS games which appear to entirely lack the ability to exit/quit/close them. One prime example of that is "Paratrooper" from 1982. I've ...
Kenas's user avatar
  • 607
45 votes
2 answers
8k views

Did IBM encourage Bill Gates to retain the rights over PC-DOS?

As is well-known, Microsoft's negotiations with IBM to deliver PC-DOS 1.0 with the original IBM PC resulted in: IBM licensing the OS from Microsoft, as opposed to purchasing it outright. Microsoft ...
Brian H's user avatar
  • 60.8k
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
  • 2,793
37 votes
7 answers
9k views

How did Apple fail to tap the business and scientific markets?

Currently reading an excellent book called Blue Magic: The People, Power and Politics Behind the IBM Personal Computer, which is just what it says on the tin; highly recommended to anyone who wants to ...
rwallace's user avatar
  • 61k
35 votes
4 answers
9k views

How much did IBM save by limiting the PC to 4.77 MHz?

My understanding is the CPU clock speed on the Intel 8088 in the IBM PC was selected as 4.77 MHz to simplify the design of the system. This despite the 8088 coming in two versions - 5 MHz and 8 MHz. ...
Brian H's user avatar
  • 60.8k
33 votes
3 answers
3k views

How was the 80186 incompatible with the IBM PC?

Wikipedia's Intel 80186 entrymentions The 80186 would have been a natural successor to the 8086 in personal computers. However, because its integrated hardware was incompatible with the hardware used ...
rwallace's user avatar
  • 61k
33 votes
1 answer
8k views

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 ...
scrØllbær's user avatar
  • 1,109
33 votes
3 answers
13k views

Why do PCs boot in 720x400 resolution?

Using my 21" Trinitron OSD, I can see that the resolution at boot is 720x400. From memory, this weird resolution is extremely uncommon if ever to be seen as a choice on software that supports ...
Eric Cartman's user avatar
  • 6,760
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
  • 61k
31 votes
5 answers
6k views

What were the differences in floppy disk formats between Amiga and IBM/PC compatible computers?

The capacity in Amiga Old File System format (OFS, OS version 1.x) was 840KB, with the Fast File System ("FFS" (!)) introduced for OS 2.x onwards able to store 880KB. The PC format stored 720KB on the ...
nsandersen's user avatar
  • 1,753
30 votes
6 answers
16k views

Is it true that control+alt+delete only became a thing because IBM would not build Bill Gates a computer with a task manager button?

Is it true that ctrl+alt+del only became a thing because IBM would not build Bill Gates a computer with a button specifically for the task manager? Making it so that Microsoft had to develop a ...
Neil Meyer's user avatar
  • 6,407
27 votes
4 answers
56k views

How can I connect a DIN plug keyboard to USB?

I have a wonderful IBM Model M keyboard, which has the best key action of all keyboards I ever used. The problem is it has the big round 5-pin DIN connector used in AT PCs. I have some PS/2 to USB ...
SF.'s user avatar
  • 7,095
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)...
Brian H's user avatar
  • 60.8k
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
26 votes
5 answers
8k views

What makes a floppy disk bootable?

A lot of web sites describe how to create a bootable floppy disk using an existing image (via dd). But what about the image makes it bootable? I'm interested in making my own bootable floppy images ...
Sydius's user avatar
  • 2,604
26 votes
5 answers
11k views

Twist in floppy disk cable - hack or intended design?

There are many documents (e.g. this) describing the twist on two-drive floppy disk cable on IBM PC compatibles. While this is not the most proud example of clean hardware design, how much of this was ...
tuomas's user avatar
  • 2,793
25 votes
5 answers
7k views

What were wait-states, and why was it only an issue for PCs?

PC compatibles in the 1980s were often advertised as having zero, one, two, or sometimes more "wait states". Zero wait states was the best. Basically, the wait-states I am asking about are due to the ...
Brian H's user avatar
  • 60.8k
24 votes
6 answers
37k 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 ...
Tomas By's user avatar
  • 2,082
23 votes
2 answers
2k views

Which is the minimum set of interrupts/functions I should implement in a replacement BIOS for a home made IBM PC class computer?

I'm at the early stages of implementing a home-made IBM PC class computer (maybe AT class, I don't know yet). The CPU will be an actual 8088 chip, but everything else (except memory) will be ...
mcleod_ideafix's user avatar
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 ...
smitelli's user avatar
  • 1,769
19 votes
4 answers
3k views

80286 real mode emulator for 8086

While trying to use a "modern" sound card (an Aztech Sound Galaxy Pro 16 II) in an XT compatible 8086 computer, I encountered the problem that the drivers and tools (like the mixer initialization tool ...
Michael Karcher's user avatar
18 votes
1 answer
947 views

How did Drive Overlay programs break BIOS disk barriers on older PCs?

I was just reading a thread on Vogons about OnTrack and EZ-Drive setup, and it occurred to me that I have no idea how they work. Please explain why the barrier existed and then how the overlay ...
Thraka's user avatar
  • 2,913