Analysis of information sources in references of the Wikipedia article "Protected mode" in English language version.
... secondly, protected mode was also incompatible with the vast amount of real-mode code around at the time.
A downside to using V86 mode is speed: every IOPL-sensitive instruction will cause the CPU to trap to kernel mode, as will I/O to ports which are masked out in the TSS.
The reason why software task switching is so popular is that it can be faster than hardware task switching. Intel never actually developed the hardware task switching, they implemented it, saw that it worked, and just left it there. Advances in multitasking using software have made this form of task switching faster (some say up to 3 times faster) than the hardware method. Another reason is that the Intel way of switching tasks isn't portable at all
... both rely on the Intel processors ability to switch tasks, they rely on it in different ways.
80386SX — low cost version of the 80386. This processor had 16 bit external data bus and 24-bit external address bus.
The purpose of protected mode is not to protect your program. The purpose is to protect everyone else (including the operating system) from your program.
Only one page directory may be active at a time, indicated by the CR3 register.
This has been impossible to-date and has forced BIOS development teams to add support into the BIOS for 32 bit function calls from 32 bit applications.
1985 Intel launches Intel386 processor
The paging process allows the operating system to overcome the real physical memory limits. However, it also has a direct impact on performance because of the time necessary to write or retrieve data from disk.
The memory access control system according to claim 4, wherein said first address mode is a real address mode, and said second address mode is a protected virtual address mode.
What is interesting is that the designers of the time never suspected anyone would ever need more than 1 MB of RAM.
The memory access control system according to claim 4, wherein said first address mode is a real address mode, and said second address mode is a protected virtual address mode.
1985 Intel launches Intel386 processor
What is interesting is that the designers of the time never suspected anyone would ever need more than 1 MB of RAM.
... secondly, protected mode was also incompatible with the vast amount of real-mode code around at the time.
A downside to using V86 mode is speed: every IOPL-sensitive instruction will cause the CPU to trap to kernel mode, as will I/O to ports which are masked out in the TSS.
The paging process allows the operating system to overcome the real physical memory limits. However, it also has a direct impact on performance because of the time necessary to write or retrieve data from disk.
Only one page directory may be active at a time, indicated by the CR3 register.
The reason why software task switching is so popular is that it can be faster than hardware task switching. Intel never actually developed the hardware task switching, they implemented it, saw that it worked, and just left it there. Advances in multitasking using software have made this form of task switching faster (some say up to 3 times faster) than the hardware method. Another reason is that the Intel way of switching tasks isn't portable at all
... both rely on the Intel processors ability to switch tasks, they rely on it in different ways.
