Questions tagged [real-mode]
For questions about switching hardware into real address mode
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 ...
How much slower was the 286 in protected mode?
I am given to understand that if the 80286 is run in protected mode, it is slightly slower than real mode, due to memory protection checks taking extra clock cycles. Just how much slower is it? Either ...
8086 assembly relative addressing issue [closed]
This tiny program puts a few A's into the text mode buffer of an ms-dos pc. But only works if the number of repetitions (CX) is loaded with a direct value. If I try to read that from memory, i.e. ...
How can I access the VGA card's ROM fonts with interrupt 10h operation 1130h in protected mode C?
I'm using Open Watcom 1.9 to write some 286 real mode, and 386 protected mode software for DOS in C. In real mode, I can retrieve a pointer to the system ROM character bitmaps in real mode using int ...
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 ...
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 ...
80286 can switch from real mode to protected mode - but why not back?
It's been a while, but I've read in a system programming book that you could switch your Intel 80286 CPU from the normal real mode to a more powerful protected mode. I clearly remember that they said ...