NASM - The Netwide Assembler

NASM Forum => Announcements => Topic started by: James2M on February 03, 2023, 09:37:50 AM

Title: What is this 64-bit real mode mentioned in Intel x86 x64 manual?
Post by: James2M on February 03, 2023, 09:37:50 AM

The official Intel CPU manual, while researching on the x87 FPU I happened to notice something interesting. It mentions a 32-bit real mode. And I'm thinking WOW, how does that work? I've always been told that real mode is 16 bits, and that there are 16bit and 32bit protected modes (and now also 64bit long mode). Is this an experimental mode that Intel was working on, but just never developed a CPU for? Or is this some kind of mode that while it does exist in Intel CPUs, the mechanism to switch to it is undocumented? Fortiva Credit Card (https://www.fortivacreditcard.net/)

Title: Re: What is this 64-bit real mode mentioned in Intel x86 x64 manual?
Post by: debs3759 on February 03, 2023, 11:23:50 PM

https://en.wikipedia.org/wiki/Unreal_mode

and

https://wiki.osdev.org/Unreal_Mode