Questions tagged [ibm-pc]
For questions about the early IBM PC, clones and compatible systems.
294 questions
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How does the capacitive sensing works on the PC / PC/XT keyboard type 2?
I am trying to replicate the IBM System/23 Datamaster keyboard using off-the shelf components. This means that I am using a 8749 instead of the 8048 and some 7400s to replace the LST/MST. For your ...
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In the original IBM PC 5150, could you put both a monochrome and CGA adapter cards?
Like the topic says, was it possible to put two different types of available video cards, MDA and CGA, into the original IBM PC 5150, and thus utilize two displays simultaneously?
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Where did the baby AT motherboard format come from?
This recent video on LPX claims the baby AT motherboard appeared overnight without any explanation. Magazines didn't mention it in 1986 and in 1987 they referred to it as if you already knew what it ...
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How does the IBM 5150 PC test the DMA device?
I have been analyzing the diagnostics tests of the precursor of the IBM PC, the System/23 Datamaster, and found that the DMA device is tested by faking a light pen strobe at a specific point of the ...
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Is MDA based on the Datamaster video subsystem?
I have read the claim (Byte Magazine, September 1990, "The creation of the IBM PC") that the IBM PC Monochrome Display Adapter (MDA) is based on the previous computer's video subsystem, ...
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Did mixing an 8 bit ISA card in a 16 bit ISA environment slow down the whole bus?
I was looking at the handbook "Writing HOT Games for Microsoft Windows" (published Oct 1994) and came across something that I'm confused by.
Specifically, Appendix A, Section 10 notes "...
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How Did 1988 PCs Achieve 12 MHz DRAM Cycles with 80 ns Chips
I'm haunted by an advertisement (on p.47 in the August 1988 issue of BYTE) for a zero wait state 12 MHz 80286 PC with 80 ns memory. How was this possible given the timing constraints of chips of the ...
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How was the first ever IBM PC BIOS image created? Can this process be replicated today?
According to dosfan, there are three known production versions of BIOS for IBM 5150 with the following datecodes: 04/21/81, 10/19/81 and 10/27/82. I am specifically asking about only the first one (...
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How did PC games reproduce PCM sounds on PC speakers using PWM when speakers had poor frequency response?
The method I am referring to is visible in videos such as these: https://www.youtube.com/watch?v=Wu5zd5fCaPA
https://youtu.be/fWDxdoRTZPc?si=cqPRdGtLAR_uAfK7&t=509
The PC speaker from what I ...
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What do these labels/mnemonics mean on Mitsumi D539W dual (3.5" + 5.25") floppy drive jumpers?
What do the jumpers control on a Mitsumi D539W drive, as in below photo?
I've looked but can't find documentation for this specific drive, which has one cable connector for 2 individual floppy drives -...
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What AT clones supported XT keyboards?
Recently, I was researching IBM PC keyboards and their compatibility. I found out that there are a lot of misconceptions online about them.
First, there are two keyboard protocols that are not ...
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Fake unshifts for 101-key extended keys - logic and current state?
(UPDATE[2025-04-01]: An essential part of the question had emerged due to the pilot (me) error to restore, at an instant, the option to show the real thing. Anyway, due to upvotes of the question as ...
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Are there keyboards with XT/AT autodetect? How is it implemented?
Nowadays, it's common for keyboards to automatically switch to either PS/2 or USB mode depending on the port the keyboard is connected to. This way the keyboard can have either connector and use the ...
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How could a program fault disable Ctl-Alt-Del on an 8088 / 286 / 386?
I remember sometimes the system would hang, and Ctl-Alt-Del didn't do anything. How could that happen?
Was it simply Application software stealing the keyboard interrupt vector from from the BIOS?
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Lowest possible chip count of an XT-class IBM PC compatible computer
The original IBM PC had a very large PCB with a lot of components, but over time various clones of this design simplified it and lowered both the area of the board and the number of components on it.
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