drive access

Woellchen · Post by **Woellchen** » Thu May 08, 2008 3:09 pm

hi
my problem is the following:
i have a kernel in protected mode written in c
my question is how to access to the drives like floppy and hard disk because i cant use int 13h anymore as you know
is there any address like 0xB8000 for the video memory?
i hope you can help me
thanks

svdmeer · Post by **svdmeer** » Thu May 08, 2008 3:16 pm

With a segment selector and pagetable pointing to physical address b8000 you can access textmode-memory. With physical address a0000 you can access graphics memory.

Woellchen · Post by **Woellchen** » Thu May 08, 2008 3:22 pm

..my question was how to access a floppy or a hard drive..

pcmattman · Post by **pcmattman** » Thu May 08, 2008 3:26 pm

You can't access disks at a memory address, because even for the text framebuffer it's all MMIO (memory mapped i/o) and there isn't any mapping for hard disks or floppy drives (because they're custom additions to the system).

You need to use CPU ports (at least, you do on x86) to talk to the hard disk or floppy drive - I highly suggest getting the ATA specification and googling for floppy drivers (I'm pretty sure the wiki has something on the floppy drive).

Woellchen · Post by **Woellchen** » Thu May 08, 2008 3:42 pm

so in fact i have to use the out and in functions in assembler?
its the only thing i want to know because i didnt know that

neon · Post by **neon** » Thu May 08, 2008 7:54 pm

Basically, yes.

btw, out and in are instructions not functions.

bewing · Post by **bewing** » Thu May 08, 2008 8:48 pm

Here is the wiki page I wrote, with instructions on the simplest method of how to use a hard disk, once you are not using the BIOS anymore.
http://www.osdev.org/wiki/ATA_PIO_Mode

Good luck.

Dex · Post by **Dex** » Fri May 09, 2008 8:45 am

See here for simple example:
http://www.osdev.org/phpBB2/viewtopic.p ... hlight=hdd