Writing Interrupts for Disk access?

[cboxgo]

Has anyone here written interrupts for disk access in their own operating system(s)? I'm trying to get a better understanding of positioning data on a hard disk without existing operating system or BIOS interrupts. I'm also trying to learn more about advantages/disadvantages using writing by sector, track, and cylinders. Ideas would be greatly appreciated.

Useful URLs on this topic would also be greatly appreciated...

 

[sarnath]

Hi CboxGO.
See the thread on "Low Level OS-independent access to
disk".

CST addressing is called 3-D addressing and can't reach
out more than 8GB hard disk space. BadBoy
( U can work out the MATH ) Thats 1 disadvantage about CST addressing...

Another small thing i know ( I'd like to share this with
others. This may occur to u as a trivial one..Anyway,
information has a tendency to be free..As per AmkG )

HARD-DISK has it's own DISK Controller which is controlled
by a SCSI card or some other. The OS or the Driver needs
to talk only with the SCSI card or any other, and need
not talk with the DISK controller. This is my understanding..
Disk Access Gurus, tell me if i am wrong. I m all
ears to hear on this topic.


Do not rejoice that ur code works.
it might be a special case of an error :-(

 

[AmkG]

Same understanding. Some controllers, in fact, don't REALLY access the real CST you pass them, they do some "translation." That is, say, if the manufacturer finds that the whole track 0 cylinder 0 is bad, then the manufacturer may instead "translate" it to another which is, say, track 8 cylinder 600 instead of completely wasting an otherwise fine Hard drive (especially since the first sector is very important). So you pass Track 0 Cylinder 0 Sector 0 and the controller accesses Track 8 cylinder 600 sector 0.

But that's an aside...

However, note that OLDER hard drives don't have a separate controller... but who still uses an ST412? "Information has a tendency to be free. Which means someone will always tell you something you don't want to know."