[Freedos-devel] How does the boot sector know the partition start

2011-09-17 Thread Decheng Fan
Hello everybody, Recently I read about two examples of MBR boot code. One is Windows 98 MBR (not yet finished reading), another is Minix MBR (almost finished reading). The Minix MBR seems more advanced, but let me skip this for now. I see the MBR code essentially loads the boot sector of the activ

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-20 Thread C. Masloch
Hi, This doesn't seem to have received any answers yet. > I see the MBR code essentially loads the boot sector of the active > partition and puts it at address :7c00. Then the boot code is > executed by jumping to that address. This is correct. > 1. INT 0x13 with AH=0x42 does extended read

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-20 Thread Decheng Fan
Hi, Thank you for so detailed explanation! This helps me a lot! I'll take time to read it more carefully and search through the Web for clearer understanding. Thanks again. Best regards, Robbie On Tue, Sep 20, 2011 at 10:30 PM, C. Masloch wrote: > Hi, > > This doesn't seem to have received any

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-21 Thread François Revol
Le 21/09/2011 06:48, Decheng Fan a écrit : > Hi, > > Thank you for so detailed explanation! This helps me a lot! I'll take time > to read it more carefully and search through the Web for clearer > understanding. Thanks again. > IIRC there is a convention that the MBR partition info (somewhere in

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-21 Thread François Revol
Le 21/09/2011 21:25, François Revol a écrit : > Le 21/09/2011 06:48, Decheng Fan a écrit : >> Hi, >> >> Thank you for so detailed explanation! This helps me a lot! I'll take time >> to read it more carefully and search through the Web for clearer >> understanding. Thanks again. >> > > IIRC there i

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-21 Thread Decheng Fan
Hi, On Thu, Sep 22, 2011 at 4:43 AM, François Revol wrote: > Le 21/09/2011 21:25, François Revol a écrit : > > > > IIRC there is a convention that the MBR partition info (somewhere in the > > sector buffer it just read) that the MBR handed control to is passed > > over to the partition boot secto

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-23 Thread C. Masloch
> 22:23 <@aljen> you mean ds:si pointing to selected partition entry in > mbr when jumping into vbr's code ? > 22:23 < mmu_man> yup Could have told you about that. At least some MBRs leave ds:si to point to the entry, which seems a random occurrence rather than an intentional interface. I thi

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-23 Thread Eric Auer
Hi, >> 22:23 <@aljen> you mean ds:si pointing to selected partition entry in >> mbr when jumping into vbr's code ? >> 22:23 < mmu_man> yup > > Could have told you about that. At least some MBRs leave ds:si to point to > the entry, which seems a random occurrence rather than an intentional >

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-25 Thread Decheng Fan
Hi, On Sat, Sep 24, 2011 at 2:16 AM, Eric Auer wrote: > > As far as I remember, the MS DOS 7.x / Windows 9x boot > sectors did use it and it is in fact intentional there. > > > In a boot sector, you could attempt to use that information; if so, > > verifying that the byte at address ds:si contai

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-25 Thread C. Masloch
> As far as I remember, the MS DOS 7.x / Windows 9x boot > sectors did use it and it is in fact intentional there. Almost entirely certain that you are wrong. Superficially checked both boot sectors in the MS-DOS 7.10 SYS.COM now (one's for FAT12 and FAT16, the other for FAT32) and they both lo

Re: [Freedos-devel] How does the boot sector know the partition start

2011-09-25 Thread Eric Auer
Hi Christian, >> As far as I remember, the MS DOS 7.x / Windows 9x boot >> sectors did use it and it is in fact intentional there. > > Almost entirely certain that you are wrong. > > Superficially checked both boot sectors in the MS-DOS 7.10 SYS.COM now > (one's for FAT12 and FAT16, the other