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