Questions tagged [ibm-pc]

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

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2
votes
2answers
257 views

What was the DRAM refresh interval on early microcomputers?

Dynamic RAM is denser than static RAM, but needs to be refreshed every few milliseconds to avoid losing data. How many milliseconds, exactly? If the answer has changed over time, then I'm interested ...
26
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5answers
3k 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 ...
4
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0answers
116 views

Is there any way to obtain the abandonware 1994 original release of Klik & Play in non-English, non-“For Schools” versions?

In the mid-1990s, I purchased a Swedish boxed copy of v1.0 (I believe) of Klik & Play in a computer store. Since that, the floppies have died and I stupidly even threw away the entire big box and ...
4
votes
1answer
316 views

What does it mean when “The Good Old Days” have several seemingly identical downloads for the same game?

This happens for numerous games. If I search, for example, for "Spear of Destiny", I get this: https://archive.org/details/TGODFloppyCollection?and%5B%5D=spear+of+destiny&sin= Four ...
26
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5answers
10k 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 ...
28
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17answers
6k 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 ...
15
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2answers
2k views

Why did the 8087 need a special socket?

The IBM PC included a coprocessor socket for the 8087 floating-point unit. Logical enough; some customers wanted to use the 8087 to make numeric calculations run faster. But why was the 8087 designed ...
3
votes
1answer
175 views

PC Task performance

What sort of performance I can expect from PC Task 4.4 on Amiga 500 + 030 50MHz MMU, 64MB RAM? Would it be possible to run Windows 3.11 / 95 and have any real use from it?
8
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2answers
507 views

Origin of Ctrl-Alt-Delete key combination to reset

The Ctrl + Alt + Del key combination to reset is known to me to work on older PC/MS-DOS PCs, some versions of Atari TOS, on runlevel 3 / multiuser.tager Linuxes (it can be disabled). The older of ...
31
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5answers
3k views

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 ...
3
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2answers
293 views

How did databases use the 8087?

A discussion on programs that used the 8087 mentions several categories I expected, and one I did not: Database programs (dBase IV, FoxBase, Paradox, Revelation) The more I think about it, the more ...
3
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1answer
343 views

What were the most common applications of the 8087?

The original IBM PC had a slot for the 8087 floating-point coprocessor. This was a somewhat esoteric feature at the time – previous microcomputers had done all their floating-point in software – but ...
11
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2answers
1k views

Was natural convection ever a consideration in orienting expansion cards?

Many computers have followed the design pattern of a backplane with expansion cards, including arguably the three most influential microcomputers ever built: the Altair 8800, the Apple II and the IBM ...
10
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1answer
251 views

Did the Harris 80C286 differ from Intel's 80286 in its behaviour?

The Harris company, well known for being an early second source making x86 chips under license, eventually produced a fully static CMOS 80C286 of their own design (later known as the Intersil 80C286 ...
2
votes
1answer
205 views

Where can I donate Old Mags and Media in bulk in UK?

I am taking advantage of lockdown(s) and scanning/imaging all old media to archive.org, but would like to donate the boxes when finished. A bit like Donating old Computer Shopper Magazines The Centre ...
6
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2answers
198 views

Are there any known 8086 systems that would dynamically switch between XTAL and EFI clocks on 8284 clock generator?

In an typical 1980s 8086 system the 8284 clock chip is typically used to generate the clock for the CPU. The 8284 has two clock sources XTAL and EFI. XTAL provides a steady clock source from a ...
2
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2answers
1k views

Why does changing a DOS/Windows EXE cause it to not run? [closed]

If I hex-edit an EXE for DOS or Windows, by adding or removing some text for example, it will no longer run. If I just change a single char around to a different one, it may run. Is this some anti-...
4
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2answers
190 views

Detecting the number of disk drives installed

When the BIOS gives control to the MBR (or the bootloader, for non-partitioned media), it passes the drive number from which the bootloader was loaded in the DL register. This number is most of the ...
11
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3answers
1k views

Default (as opposed to physical) read/write heads - what are they?

The Seagate U Series hard disk Product manual states that the drive has 16 "Default read/write heads" while it has 4/3/2/1 "Physical read/write heads" (depending on actual model). ...
6
votes
3answers
443 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 ...
1
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2answers
202 views

Does the Sound Blaster Live! Value had hardware support for Adlib/OPL3?

As I m buying a computer without an onboard sound card, I m thinking about using my old Creative Sound card from 21 years ago and buying a pcie riser adapter instead of a modern sound card (I m ...
15
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7answers
6k views

Why did the IBM PC have an internal power supply?

Microcomputers run off low voltage DC, but usually came with a power supply to produce a suitable DC current from the mains AC voltage. It was usual among early home computers to supply an external ...
26
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3answers
5k 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 ...
9
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2answers
531 views

What year was my old, long-lost IBM PC born? 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 ...
3
votes
1answer
197 views

Best way to swap IBM PC case badge?

A while back, I purchased an original IBM PC (5150). The seller had an improper top case or badge on it, as the badge actually said it was an XT (5160) instead. After confirming that it is indeed a ...
6
votes
1answer
380 views

Was it ever possible to access the full EGA color space in 200-line modes?

It's long been an established fact that the EGA only had four memory planes, which limited the number of colors on the screen to (24) 16. The best compatible monitors at the time had six TTL color ...
2
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2answers
277 views

First 386 PC on sale in the UK

In the early days of personal computers, there was something of a delay in the technology crossing the Atlantic, and when American computers did arrive in the UK, they tended to be expensive relative ...
1
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1answer
63 views

Part number / model for IBM PC 350 keyboard

what was the part number or model of the original keyboard shipped with IBM PC 350? Trying to restore the full set.
5
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1answer
381 views

Which were the best selling early MS-DOS PCs apart from the IBM PC?? [closed]

The IBM PC in 1981 was rapidly followed by a rich ecosystem of computers with x86 CPUs running MS-DOS, not all of which were compatible at the hardware level. There is a list of some early MS-DOS ...
8
votes
2answers
760 views

Could CGA synchronize with vertical blank?

According to http://www.vcfed.org/forum/showthread.php?62049-The-myth-of-the-vertical-retrace-interrupt-on-EGA-VGA IBM first implemented a vertical retrace interrupt on the PCjr in 1984. That ...
8
votes
1answer
283 views

Lotus 1-2-3 and Microsoft Flight Simulator as unofficial compatibility benchmark?

Do I remember correctly about an unofficial but popular test of "PC compatibility" in the early 1980s? Basically if a machine could run vanilla versions of both Lotus 1-2-3 and Microsoft ...
20
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2answers
3k views

Did playing sounds on the PC speaker keep the CPU busy?

The IBM PC and early successors came with an internal speaker that could play simple sounds. According to https://en.wikipedia.org/wiki/PC_speaker However, because the method used to reproduce PCM ...
20
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3answers
2k views

How was the 80186 incompatible with the IBM PC?

According to https://en.wikipedia.org/wiki/Intel_80186 The 80186 would have been a natural successor to the 8086 in personal computers. However, because its integrated hardware was incompatible with ...
8
votes
1answer
437 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 ...
12
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3answers
2k views

What was the second most common incompatibility in MS-DOS machines? [closed]

When the IBM PC was released, it did not take long for people to figure out that there would be a big market for compatible machines. The first wave relied on MS-DOS as the compatibility layer. The ...
11
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2answers
3k views

Are BIOS ROMs interchangeable among different vendor's PCs?

For PC/AT, 80386, and 80486 machines from the late-1980s through early 1990s (e.g. retro machines, not modern), can you expect to pull a BIOS ROM from one machine and have it work fine in a different ...
4
votes
1answer
240 views

Back in the day, were games coded to run better with more (not faster) RAM? [closed]

Let's say the year is 1999 or something like that. I have a PC with 400 MHz, no graphics accelerator and 64 MB RAM, and try to run some Need for Speed game or something. I notice that it goes laggy. ...
22
votes
2answers
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 ...
7
votes
1answer
310 views

IBM PC 5150 board layout

How did the parity check DRAM chips work? In particular, is there a reason for the gap in the motherboard (IBM calls this system board) between the parity check DRAM and the "normal" DRAM ...
26
votes
3answers
3k views

What were the HW specifications for the actual PC speakers, before they were replaced by buzzers?

Back in the early 2000s, I remember that, what were at the time older, PC cases had actual loudspeaker instead of the buzzer, which was popular as the PC speaker on the PC cases of the time period. ...
31
votes
3answers
10k 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 ...
8
votes
1answer
542 views

Was there ever a functional EGA emulator for the Hercules graphics card?

I used to use a CGA emulator (don't remember which one it was), that could show some gfx even in EGA/VGA-only games (when I selected EGA mode). I remember my frustration seeing some garbled graphics ...
0
votes
0answers
105 views

Portable 386 that only ever beeps continuously; no video

I've acquired a late-80s portable 386 with builtin LCD in unknown working state. It only ever beeps continuously on boot, with no picture on either the built-in LCD or an external VGA-connected ...
13
votes
3answers
1k views

PC/AT two DMA controllers - what is the purpose of cascade channel and how did it work?

Why did the design need to reserve one channel for cascade, how did it work and what exactly was going on there?
56
votes
2answers
5k 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
7k 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 ...
1
vote
2answers
297 views

Performing 16-bit port I/O on the RTC

Why can’t the RTC (0x70, 0x71) read and write 16 bits at a time? For example: mov ax, 0xa8f out 0x70, ax I have found in a 286 BIOS that did this (BIOS ID string: S286-6181-...
5
votes
1answer
152 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 ...