Questions tagged [ibm-pc]

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

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52
votes
2answers
4k 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 ...
25
votes
7answers
6k views

Purpose of turbo switch on systems unable to slow to 4.77 MHz?

I have a PC with an Intel P133 (133 MHz). The motherboard (PcPartner MB520NH) only allows for it to be slowed down to 75 MHz at the least via jumper settings, but no lower. Yet the PC's case has ...
30
votes
3answers
8k 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. ...
22
votes
4answers
4k views

Why was NEC able to wrestle PC graphics standards away from IBM?

The dominant standards for PC graphics in the 1980s were the ones introduced by IBM. This included MDA and CGA with the original IBM PC, followed by EGA shortly after the PC/AT, and then VGA with the ...
4
votes
1answer
96 views

Why does MS-DOS 5.0 EDIT hang on my XT-class machine with a German 102-key keyboard?

Most times whene I call EDIT on my XT-class machine with MS-DOS 5.0 installed on the hard disk, the menus of EDIT appear, but the window that should contain the file contents stays blank and the ...
5
votes
2answers
743 views

Could early nineties PCs access raw CD bitstream?

In the early nineties, as discussed in What specific technical advance(s) allowed PCs to play "Full-screen full-motion" video? it became commonplace for PC games to use the storage capacity ...
12
votes
2answers
1k views

Hard coded hard drive BIOS geometries

Most old BIOSes on PCs and compatibles provided means to enter hard drive geometries (cylinder/head/sector as well as more esoteric things like write precomp) when configuring the machine. Some (AMI ...
22
votes
4answers
6k 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)...
0
votes
2answers
168 views

IBM PC 5150 motherboard labelling

The motherboard of the IBM PC 5150 has labels of letters followed by numbers. What are the letters representing? Examples being U1, P1, C1, T1 and Y1. I am trying to ascertain which component is the ...
9
votes
2answers
460 views

What PC graphics tech outperformed Sega Dreamcast in 1999?

The Sega Dreamcast was released in 1999 (1998 in Japan) at just the time that the competition for 3D graphics on PCs was intensifying. It's my assumption that a high-end 1999 Pentium II PC with 3Dfx ...
9
votes
2answers
633 views

How can I read a 5-1/4 drive on 1996-2007 equipment?

In my organization's archive I just found some 5-1/4" floppies, presumably IBM PC 320/360k. They contain information that we have on paper, but I'd really like to have on electronic media, not least ...
59
votes
3answers
18k views

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 ...
42
votes
2answers
9k views

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 ...
12
votes
1answer
1k views

What manages Upper Memory Blocks (UMBs) in MS-DOS?

I had always assumed that EMM386.EXE was responsible for managing the Upper Memory Blocks - UMBs - the memory space between 640KiB and 1MiB in real mode x86. For example, on MS-DOS 6.22, help emm386....
17
votes
4answers
2k 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 ...
2
votes
1answer
238 views

Power switch color on IBM PS/2 red vs white?

Why do some IBM PS/2's have a red switch, while others have a white switch? Does the red or white power switch on the power supply signify something about the model number, CPU, or options that the ...
7
votes
2answers
564 views

Looking for a 90's shooter-platformer game

Back in the 90's I remember playing a 2d shooter-platformer game on my family's home computer. I sucked at the game, and as far as I remember I never managed to beat the first level. The details I ...
6
votes
2answers
368 views

Does anyone remember an early 90s side-scroller with a player-controlled ED-209-like robot?

I remember playing a side-scroller at a Babbage's at the mall (on probably a sweet Compaq; I don't think it was on a C64, an Amiga, an Apple, or anything more exotic), probably around 1993, where the ...
27
votes
2answers
10k views

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 ...
3
votes
1answer
144 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 ...
3
votes
0answers
155 views

Can a bootable Win9x HDD be made interchangeable between PCs?

Normally, Windows 9x must be installed on each PC individually so that it can be loaded/configured with the appropriate set of drivers. I'm wondering if there is any way to make a boot HDD that can be ...
13
votes
3answers
1k views

What are the electrical characteristics of a PC gameport?

I'm considering building some custom gizmos to connect to the gameport on my retro-hobby PC (SNES controller adapter, macro/turbo box, etc.) but I haven't been able to find much information on details ...
8
votes
2answers
2k views

Are game port joystick button circuits more than plain switches? Is this one just faulty?

I'm building a custom interface unit for a game port joystick. To use/test it, I have a CH Products Mach III. (This is the IBM PC version, not the Apple version.) I purchased the joystick for this ...
91
votes
1answer
26k 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 ...
66
votes
8answers
17k 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 ...
15
votes
5answers
3k 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. ...
27
votes
6answers
15k 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 ...
18
votes
4answers
1k 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 ...
42
votes
2answers
4k views

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 ...
23
votes
10answers
4k views

Why was hardware diversification an asset for the IBM PC ecosystem?

The IBM PC was cloned very early on, and many third parties made hardware peripherals. This required users to run an OS, install drivers, manage IRQs and hardware bus addresses, etc. Why was this a ...
6
votes
1answer
259 views

The IBM RAM with non-standard pin layout

One and half decade ago I had an black IBM Thinkcentre tower. The specs were: Pentium 4 2.66 GHz 256 Mb IBM RAM (which later got upgraded into 512 Mb RAM), 40GB HDD, XP Pro SP3, GeForce 2 MX 400. ...
43
votes
8answers
10k 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 ...
51
votes
3answers
8k 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 ...
7
votes
3answers
356 views

What was the standard size of a PC clone's badge indent?

Generic beige-box PC clones like the ones pictured here often had an indent for the manufacturer's badge to be stuck on. Were these all a standard size, and if so, what were the dimensions?
7
votes
1answer
302 views

AT system without -5v

I have recently built a 80386 system. Lacking any AT PSU I connected a PicoPSU using an ATX->AT power adapter. Only card connected was a gpu (Trident TVGA 9000i). System performed BIOS checkup ...
6
votes
1answer
1k views

What was the first third-party commercial application for MS-DOS?

What was the first third-party commercial application for MS-DOS intended for IBM PC-compatible computers?
13
votes
1answer
6k views

What is the oldest commercial MS-DOS program that can run on modern versions of Windows without third-party software?

What is the oldest commercial MS-DOS program that can run on modern versions of Windows (such as Windows 8.1 or Windows 10) without third-party emulators?
6
votes
4answers
2k views

High-end PC graphics circa 1990?

I remember CAD being a major driver for PCs with high-end graphics cards; specifically AutoCAD was rising quickly in popularity around 1990 as PCs were able to compete with very costly CAD ...
2
votes
2answers
145 views

ISA Extension cards using more than 64kB

Related to my previous question around VGA framebuffer being limited to 64kB I started to wonder if there was any extension cards (or similar) using more than 64kB of address space in linear fashion, ...
8
votes
3answers
1k views

Why VGA framebuffer was limited to 64kB window?

VGA framebuffer was fixed to 64kB at A0000h. Right after that there’s MDA/CGA framebuffer at B0000h. I am not sure, but I recall VGA did have to support CGA and its framebuffer, but was there any ...
51
votes
6answers
16k 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?
13
votes
4answers
5k 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 ...
21
votes
4answers
4k 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 ...
6
votes
1answer
518 views

When did MS Windows get Dual Monitor support?

I remember one of the features I admired on the Macintosh in the late 80s was support for multiple displays. First time I saw this was on an SE/30, using the internal display along with a big external ...
2
votes
2answers
812 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) ...
3
votes
1answer
327 views

Why did CGA RGBI output leave DAC to the monitor?

CGA on the original IBM PC produced sixteen colors, one bit each for red, green, blue and overall intensity modifier. The preferred output device was the later-arriving 5153 color monitor, which ...
8
votes
1answer
395 views

What's the fastest way to ignore keypresses?

I'm writing a game for the IBM PC (running MS-DOS), complete with fancy cutscenes. Unfortunately, though, the keys pressed during those fancy cutscenes are carried out once the fancy cutscene has ...
5
votes
5answers
419 views

Did the PC/AT-bus use its expanded address space?

The system bus of the IBM PC had 8 data lines and 20 address lines, in a logical correspondence to the 8088 CPU. The AT added a second inline edge connector to expand this to 16 data lines and 24 ...
4
votes
1answer
365 views

Did the 286 go out of its way to follow the 8088 bus protocol?

In general, different CPUs don't use the same bus protocol. A 16-bit CPU would not in general be expected to use the same protocol as an 8-bit CPU. For example, the 68000 would not be expected to use ...
4
votes
3answers
856 views

Gotek drives for MS-DOS (plus few more constraints)

I have installed two gotek device instead of two old unworking floppy disk drives (in particular on an Olivetti PCS 86). And the result is something like this: (The one on the right should the the A:...