Mark Knecht <markkne...@gmail.com> [11-01-21 21:04]: > On Fri, Jan 21, 2011 at 11:40 AM, <meino.cra...@gmx.de> wrote: > <SNIP> > > Hi Mark, > > > <SNIP> > > I thought (which implies "I dont know for sure"), that the BIOS do > > enable/disable certain features, the kernels reads that settings and > > act accordingly -- but definitely this is not true for all settings. > > > > Certainly true for some hardware, like clocks, etc. > > For disk controllers AFAIK the goal is to give the boot loader a > chance to boot. After that it doesn't, in general, matter what the > BIOS did. > > For instance, modern SATA controllers use DMA. BIOS and older > operating systems like DOS didn't know much, if anything, about DMA, > so BIOS leaves that turned off. The kernel turns that on. > > > Does the contents of a harddisk differ when written with AHCI > > compared to a disk which is written with IDE? > > > > TTBOMK no. Other things like file system type, etc., change what's on > the disk, but the disk store so many bytes/sector and that's just the > way it works. > > > > If NO _AND_ only the kernel sets the AHCI- odr IDE-protocol, then > > the harddisk should be readable in either case. > > > > Certainly, which is why you could build this system using AHCI and > then move it to some other system and read the disk using DOS. > (Assuming DOS could understand the file system like FAT, etc.) > > > If the BIOS _and_ the kernel settings are defining, how to talk > > to the disk, then it may happen, that there is only the "sound of silence" > > between kernel and hardware if before the BIOS set up the SATA-chips > > differently to what the kernel wants to talk. > > > > BIOS sets up the system hardware so the boot loader can get the kernel > image off the disk. The kernel is read into memory using these > settings. At that point there aren't any more disk reads for a while. > The kernel executes and starts resetting the hardware through driver > loads, etc. This is why one controller could be set to use a SATA > Drive by itself or RAID. > > > But again, these are only thougts drifting in the dark. > > > > I tried to shed some more light (for getting greater shadows ;) ) > > by posting my question here... ;) 8) > > > > May be I should do some more stupid things??? ;) > > > > Ain't no such thing a stupid question. Only thing to do when > experimenting is ensure you aren't risking data you care about. I > would do these experiments on a new clean system. I would not do them > on a system that has stuff I care about unless I had known good > backups. > > > Thanks again for your help and your words, Mark! > > Have a nice weekend! > > Best regards, > > mcc > > > > You too sir! > > Cheers, > Mark >
Last thing which remains is: Why does the help of the kernel says to both AHCI-settings: "If unsure, say N"... ?
