Questions tagged [x86]
The Intel x86 family of architectures in general. Contemporary systems are OFF-TOPIC! Use the specific architecture’s tag if applicable.
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Identifying late 1990s embedded 486 UNIX-like system
I'm trying to identify the operating system on a Thermo-CRS C500 robot arm controller. From the specifications I know it runs on a 100 MHz 486 processor, and has 4 MB RAM and 2MB of flash/NVRAM ...
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What’s the last x86 CPU that didn’t place a limit on the size of a single instruction?
Although useless, it’s widely known the first Intel and derivative CPUs like the Z80 didn’t set a limit on the instruction size. This means that it was possible to fill the whole RAM/ROM with a single ...
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Are .COM executable binaries real mode or protected mode?
Windows and DOS binary executable files with the .EXE extension have an MZ header in them and nowadays also a PE header.
But before these there used to also be .COM binary executable files and they ...
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First x86 Software Development Manual
These manuals are now called “Intel® 64 and IA-32 Architectures Software Developer Manuals”, and the current version is 71. What was the original name of this manual and when was it released?
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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....
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How does the ‘real mode flat model’ work?
I am interested in old Intel processors. I'll try to be as concise as possible.
I have been studying both Jeff Duntemann's Assembly Language Step-by-Step - Chapter 4 and Modes of Memory Addressing on ...
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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.
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What 486 motherboard is this, with American Megatrends BIOS identifying is DPAQ-6156-043090-KF?
I've got an early 486 motherboard that doesn't seem to have a manufacturer name or FCC number on it and I'm having trouble identifying it.
I've placed some photos of the motherboard in this Imgur ...
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3 beeps on a 486 computer with an American Megatrends bios?
So far I've figured out that means something about the ram bit I haven't been able to figure out what the problem is
Edit: video link
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What was the first x86 CPU to use a cache of any kind?
I believe the 80286 had a prefetch instruction queue, but did it have any other forms of cache? Was the 80386 the first x86 CPU to have a cache?
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What was the first Intel x86 processor with "Base + Index * Scale + Displacement" addressing mode?
As the title says, what's the first x86 processor from Intel that supports the following addressing mode?
mov %reg, 8(base, index, 4)
^^^^^^^^^^^^^^^^^
where the content of %reg will be ...
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Why weren't discrete x86 CPUs ever used in game hardware?
Please don't point out APUs with x86_64 cores used in current generation game consoles, these are not part of the question
I cannot recall a single arcade system or game console that ever used x86 ...
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What does the "x" in "x86" represent?
I have read the following in the x86 Wikipedia page:
The term "x86" came into being because the names of several successors to Intel's 8086 processor end in "86", including the 80186, 80286, 80386 ...
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What was the last x86 CPU that did not have the x87 floating-point unit built in?
This Wikipedia page says the following:
Most x86 processors since the Intel 80486 have had these x87
instructions implemented in the main CPU
So the above quote implies that some CPUs that were ...
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Can an x86 CPU running in real mode be considered to be basically an 8086 CPU?
When an x86 CPU is running in real mode, can it be considered to be basically an 8086 CPU (or maybe 8088)? Or are there differences between the two?
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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 ...
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Examples of operating systems using hardware task switching of x86 CPUs
Intel IA-32 architecture a.k.a. x86 offers hardware task switching capabilities since 80386. It includes TR (task register), memory segmentation features such as Task State Segment, task gates, call ...
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Does anyone have an x86 EGA draw pixel routine?
So far, I have gotten by with using the BIOS draw-pixel routine here: http://stanislavs.org/helppc/int_10-c.html
This works of course, but I can't imagine that commercial games used this BIOS call as ...
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How to use the "darker" CGA palette using x86 Assembly?
For those of you retro developers out there, I am having a hard time figuring out how exactly to select the "darker" color palette in 320x200 CGA mode. Here's what I have so far:
setup_cga_graphics:
...
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What was the first publication documenting AT&T syntax assembly language?
What was the first publication to document what is (now) known as AT&T syntax assembly language?
user11467
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SYSENTER/SYSEXIT broken on Pentium Pro and Pentium II?
I was just reading What is linux-gate.so.1?, and it says this:
Intel recognized this problem early on and introduced a more efficient system call interface in the form of sysenter and sysexit ...
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Reason behind "ASCII Adjust" instructions being ASCII and not BCD?
I'm just curious if there was ever other instructions that were more ASCII-centric than the CISC associated ones we're left with now?
Specifically, all the Binary Coded Decimal (BCD) instructions ...
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How do you put a 286 in Protected Mode?
From the Art of Intel x86 Assembly, Page 149,
The 80386 added four control registers: CR0-CR3. These registers extend the msw registers of the 80286 [...]
The book says earlier that,
The 80286 ...
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x86 as a Pascal Machine?
From this answer by gsg about the usage of certain x86 instructions:
Note that the x86 was originally designed as a Pascal machine, which is why there are instructions to support nested functions (...
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Mysterious things happening to stack when running a debug session
When I run a debug session using FreeDOS and DEBUG.EXE, I get a session like the following. I've added a description of what I saw as annotation on the image. Each step, I've printed out the stack ...
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The start of x86: Intel 8080 vs Intel 8086?
Why is it said that all modern Intel processors of the x86 family are said to descend from the Intel 8086 and not the Intel 8080? From the Wikipedia article on the Intel 8086,
The 8086 gave rise to ...
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Can x86 processors run 8-bit applications?
I was wondering if it is possible to run 8-bit applications within QEMU. I know that the x86 architecture can run 16-bit applications, but can it also run 8-bit applications?
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