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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What is this PSU connector? Compaq Portable motherboard
I've lost the PSU wiring harness to my Compaq Portable motherboard in a move and I'm trying to figure out what connector this is. Here's a picture with some AT-era Molex connectors for perspective.
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What does an ADC (add with carry) instruction following ADD do?
I have found this line in an old 16-bit DOS application (likely to have been generated by Borland Turbo C compiler) and I want to understand the purpose of it:
mov dx, [bp+var_192]
mov ax, [bp+...
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What is the most performant "32-bit only" x86 CPU? [closed]
I am thinking of building an era appropriate early/mid-2000s gaming PC. One requirement is that the CPU should not support x86-64 instruction set, only the 32-bit instructions can be used.
My guess is ...
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How did 16-bit MS-DOS programs use a large (> 64KB) stack?
The "large" memory model of x86 allowed a program to have multiple code segments and multiple data segment, using far calls to jump across code segments, and far pointers to access data from ...
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Did the i186 use interrupt 6 for invalid opcodes?
I don't recall where from but at some point I was under the impression that the Intel 186 processor used interrupt 6 for invalid opcodes.
However, there's the HP 95LX that uses a NEC V20. NEC V20/V30 ...
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Did any x86 CPU optionally trap unaligned access?
x86 CPUs have always supported unaligned load/store.
Early RISC CPUs didn't. So imagine writing portable code on a 386. It seems to work fine, but how do you know you haven't accidentally misaligned ...
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The move to protected mode on x86 [closed]
When I learned programming, the programmer of the CPU had direct memory access. That is, the Z80, the 8086/8088, 6502, and so on. I don't know of any real use of the 186, but at least the 286 ...
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Why did Steve Jobs choose the Motorola 68030@25 MHz for the first NeXT Computer in 1988 and not an Intel 80386DX@25 MHz processor?
Was the reason because he knew the 68K from the Macintosh, or were there other reasons that spoke in favor of the 68030 and the additional 68882 floating-point coprocessor?
The i386, along with a 387 ...
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How do you find the EBDA address?
Normally, the "Extended BIOS Data Area" (EBDA) is located at the segment stored at 0x0040:0x000E, but this is only true for EISA and MCA systems (at least that's what I found in various ...
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Were there any PCs using the i376?
The Intel 80376 was an x86 CPU that didn't support Real Mode or paging. It was targeted for embedded applications and it wasn't very successful at that (the 80386EX overtook it).
Under these ...
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Creating 8086 binary larger than 64 KiB using NASM or any other assembler
For fun I'm developing an IBM PC emulator. I would like to test all instructions to see if I implemented them correctly. For most instructions this is straight forward, for "FAR CALL/JMP" it ...
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What is the best way to set up multiple operating systems on a retro PC?
I have an old Pentium II computer, and I would like to set it up as a retro gaming machine, but I would also like to play around with old distributions of Linux, OS/2 and other operating systems.
What ...
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Is it possible to trap 387 FPU opcodes on a 287 connected to a 386?
The 8087 and 287 FPUs were designed before the IEEE 754 standard was released. Because of this, they contain some instructions which are not compliant with it. When the 387 was released in 1987, it ...
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Who designed the ALi M1386SX core?
The ALi M1386SX is a 386 compatible microprocessor. I believe it was released around 1995, rather late for a 386 but since it was targeted at the embedded market (e.g. word processors and point-of-...
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How can a 32-bit x86 CPU start with reset vector 0xFFFFFFF0 even though it starts in 16-bit real mode?
As far as I know, x86 CPUs start up in 16-bit 'real' mode (maybe some don't).
The reset vector is 0xFFFFFFF0 (in most CPUs and in this context)
In this 16-bit real mode, we can only access 16 bit ...
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