Questions tagged [ibm-pc]
For questions about the early IBM PC, clones and compatible systems.
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Was there ever any reason to wait 30 seconds to restart a c.1995 PC?
I owned a PC in the mid-to-late 90s, and while everyone said when you turn it off and back on again, count to 30. But it also had an instant reset button down below. Was there ever really any risk ...
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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 ...
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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 ...
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3
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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 ...
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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 ...
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63
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7
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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 ...
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7
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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?
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3
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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 ...
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59
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4
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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 ...
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What is the "two-drive trick" that can read Amiga disks on a PC?
Standard belief is that the floppy disk controllers used on PCs are incapable of reading Amiga floppy disks, due to the PC disk controller expecting a very specific low-level format of disks, whilst ...
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Why was preemptive multitasking so slow in coming to consumer OS's?
Preemptive (rather than cooperative) multitasking was a highly-touted feature for PC's in 1996, with its inclusion in Windows 95 for the first time. It was also highly-touted for 2001 Macs when ...
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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 ...
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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 ...
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Locked-up DOS computer beeped on keypress. What mechanism caused that?
Long time ago I had an old IBM PS/2 that I had fished out of a dumpster. It ran IBM DOS 5.0 and was a solid little machine. Occasionally I would encounter the following scenario, and I recently ...
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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 ...
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45
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2
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Why were some early PC 3D cards unsuitable for 2D graphics?
Some of the early PC 3D graphics cards such as the 3dfx Voodoo Graphics cards had a passthrough port to enable them to switch to a secondary card to display 2D graphics.
I am curious to know why these ...
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4
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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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4
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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's the origin of terminating strings by setting the high bit of the last character?
I was looking at a hex dump of the ROM BASIC from the original IBM PC and found some byte strings like this (ASCII dump is on the right):
50 52 49 4e d4 9d 4c 49 53 d4 9e 50 4f d3 1b 45 PRIN..LIS.....
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What caused older computer fans to be so much louder than they are today?
I had one of those bulky IBM 486 PCs in the mid-1990s. Desktop form factor. I think it was probably made somewhere in 1992. It made a lot of noises, pleasant ones to me, such as mechanical hard drive ...
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7
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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 ...
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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'...
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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, ...
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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. ...
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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 ...
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33
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18
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What were the real competitors to the early IBM PC?
As I understand it, PC was not really competitive with Home computers until the 90’s. The PCs rise in popularity in the 80s must have been mainly in the business world.
So during that time, what ...
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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 ...
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5
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Did IBM originally plan to use the 68000 in the PC?
One of the big turning points in the history of the industry was IBM choosing the Intel 8088 over the Motorola 68000. Given that most people outside IBM considered the 68000 preferable, there has been ...
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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 ...
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33
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1
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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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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 ...
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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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Why did the monsters have "infinite invisible pillars" of hitboxes vertically in all versions of the DOOM engine?
Even in the last version of the DOOM engine, v1.9, used for Final DOOM, there is this strange limitation in which all the monsters have an invisible, infinitely tall "pillar" above and ...
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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 ...
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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 ...
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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 ...
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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 ...
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Looking for PC graphics demo software from the early 90s called "Unreal"
Back in the early 90's I remember downloading a graphics demo called, I think, "Unreal". This was on DOS on a standard PC and probably downloaded from a BBS.
Identifying information:
It ran for ...
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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 ...
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Did the original MS-DOS Quake not have a menu item for freelook, and if so, why?
I know that Quake (the 1996 MS-DOS game) is a "full" 3D engine, and always had some kind of mouse support.
However, even the original Wolfenstein 3D from 1992 also had mouse support from the ...
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How to get started writing C for the IBM PC in 1980-81
Suppose it's late 1980 to early 1981, you've got some software you want to write for the IBM PC which will be released later in 1981, want to get started ASAP, and believe C is the right language for ...
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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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Why separate cursor keys?
The original IBM PC keyboard didn't have separate cursor keys; the numeric keypad doubled as such. It wasn't long, however, until a new keyboard was introduced that did have separate cursor keys (so ...
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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 ...
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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 ...
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7
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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 ...
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5
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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)...
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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 ...
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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 ...
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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 ...
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