A new release already?

A new release is coming up on the horizon. We now have the date of Friday 4th of November 2011 planned for the release of Andromeda-0.1.1.

This will feature a brand new paging system, a new memory mapping system, minimal ACPI support and basic support for the Advanced Programmable Interrupt Controllers (APIC).

The paging system has been made in such a fashion that the memory requirement scales to the pages requested, instead of permanently occupying 4 Megs of RAM.

The same goes for the new memory map, and did I already mention it is based on the size of the actual physical memory!

This means that we always occupy 0.2% of physical memory available for the memory map, and depending of the amount of virtual memory usage a little bit more for the page tables.

Also we've conjured up a way to put the kernel at 3 GiB. It's called the overflow trick. The principle behind it is pretty simple. All you do is set up a segment which maps memory address 0  to the 3GiB location and make it 4 GiB long or so. Then you jump into the higher half code.

Simple as that. All you need to do is page the code to both low and high memory, disable the overflow trick and unmap the low memory code, leaving only high memory in place.

Whenever some low address is required, all you need to do is add 1 GiB to the address and the 32-bits integer flows over when the segment is applied, and the correct pointer is used.

Simple, stable and effective (do watch out with virtual machines that don't properly emulate the 32-bits overflow, they can be a real pain sometimes).

The ACPI support is created by Michel Megens, so not much for me to mention on that part. The same pretty much goes for APIC support.

And speaking of dates! My birthday was last Sunday (October 30th) at which I turned 19!