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Questions tagged [x86]

x86 is an Intel CPU architecture that originated with the 16-bit 8086 processor in 1978. Today, the term x86 is used generally to refer to any 32-bit processor compatible with the x86 instruction.

x86 is a family of instruction set architectures[a] based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introduced in 1978 as a fully 16-bit extension of Intel's 8-bit 8080 microprocessor, with memory segmentation as a solution for addressing more memory than can be covered by a plain 16-bit address. 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 and 80486 processors. https://en.wikipedia.org/wiki/X86

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Reason for x86 reset vector being at 0xFFFFFFF0 instead of 0xFFFFFFFF

The top answer to this question on Super User gave an explanation that was satisfactory to me at first as to why the reset vector is not at address 0 (afterwards , I realized that it doesn't why the end of RAM couldn't be put at 0xFFFFFFFF and then…
Melab
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Fan-out of the Intel 8086

I'm studying Intel 8086 processor. I can't understand why the "Fan-out" column is like that in the table below I understand that only one "74 family" chips or five "74LS family" gates can be connected to 8086 output pin. 8086 can sink up to 2.0mA.…
hskim
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Upload ASM code on Intel 8086 chip

I have been struggling to find a method to actually run any assembly code on my 8086 chip. I have an 8086 chip and I am trying to implement it on hardware to power up a LED or anything simple. On Proteus's simulation, this is easy to do because…
Mora
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x86 Motherboard Bring Up - Intel Tiger Lake UP3 CPU

For those who has experience with Intel x86 motherboard design and bring up. I'm in the middle of motherboard bring-up that has Intel Tiger Lake UP3 CPU. Seems like I had a good run so far at power-up sequence. here is a list of all power rails \…
Firas Abd El Gani
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Accessing odd address memory locations in 8086

I am a beginner in microprocessors. Apologies if my question is too naive. The memory section of the 8086 processor is divided into two segments: even and odd to allow the CPU to fetch 16 bits in one clock cycle. When a 16 bit word is to be read…
Sathvik Swaminathan
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IO port register whose address is software defined (x86)

I want to do something that I assume must be fairly common in digital logic/bus design. It’s for a new expansion card for an old 8088-based computer. This isn’t some kind of college homework project. I want to create an 8-bit R/W IO port register…
David00
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Intel 8042: what are "test inputs"?

I've implemented a driver for the Intel 8042 (keyboard controller in the IBM PC AT). The IBM 5170 (PC AT) Technical Reference served as my, well, reference for that. The output port and the test input port both contain "test inputs" (pp. 1-44): I…
cadaniluk
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Effective Address calculation time on 8086/8088

I've started designing an implementation of an 8088 from scratch with the goal of being cycle-exact. I can understand the reasoning behind the number of clock cycles for most instructions, however I must say I'm quite puzzled by the Effective…
Matthieu Wipliez
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Why ARM cores consumes relatively lower power than x86

Why ARM cores consume little power compared with x86 CISC implementations? What are the valid reasons? because of it's fabrication technology? Could this be right? ARM cores have been fabricated on various fabrication technologies worldwide even…
Standard Sandun
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Why does IBM PC XT use advanced memory and IO write strobes instead of normal ones?

I'm trying to dig into the early IBM PC's arhictecture, and got stuck with one thing that is not really clear to me. Every PC XT schematic I saw, including the original one from "IBM 5160 Technical Reference" use AMW and AIOW (sometimes also…
Linol
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maximum memory supported by processor - why often stated less than 1TB?

I want to understand technical details of limitations of maximum memory size a system / processor can support. Below what I was able to find via web search to date Wiki: Modern 64-bit processors such as designs from ARM, Intel or AMD are typically…
Martian2020
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Reverse-engineering VGA

I got a x86-based firewall, produced by Stonesoft. It has serial interface, but it would be easier to install new operating system if I would get VGA output from the device. I discovered promising looking header on the PCB, labeled "J11 VGA". It's…
Zokol
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What is Pipeline Flushing in microprocessors

I am reading the book "Writing Operating System from Scratch" by Nick Blundell. In one of the chapters, it is explained how we make transition from 16bit mode to 32bit mode. It says that before moving to 32bit mode we should ensure that all the…
sarthak
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memory segmentation in 8086

If the external memory (1 MB) in 8086 based system is segmented into code, data, stack and extra which are all 64 kB, what do we do with the rest of the memory? Does it go waste?
saurabh
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Internal differences between CPUs of the same architecture

What is the difference between, for example an Intel i3-4005U (1.7 GHz) and an Intel i3-4025U (1.9 GHz)? These CPUs are from the same generation, have the same amount of cores, cache, iGPU, and supported features with the only difference being the…
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