From: nowhere@nevernet.at   
      
   On 31/03/2022 22:46, muta...@gmail.com wrote:   
   > On Friday, April 1, 2022 at 12:31:38 AM UTC+11, wolfgang kern wrote:   
   >   
   >>> Is that the right approach?   
   >   
   >> the BIOS may be able to get correct geometry data   
   >> by using Identify-Device (you can do that as well).   
   >>   
   >> CHS<->LBA conversions must be aware of faked head-   
   >> numbers,it were quite common to abuse heads>>tracks   
   >> to achieve a larger CHS range. IIRC std-limit=2GB.   
   >> 24 bits addressing 512 byte sectors: 2^24*512=8GB   
   >>   
   >> If the CHS value in the MBR is wrong then blame the   
   >> formatting tool. But perhaps you misinterpreted it.   
   >   
   > My MBR uses LBA (I will replace it with a CHS version   
   > when I have one), so I only notice a problem when I   
   > get to the VBR.   
      
   my formatting uses both CHS and LBA regardless of actual   
   disc size (when CHS is set to limit it's ignored anyway).   
      
   > The formatting tool works fine, as my disk boots even   
   > on real hardware.   
   >   
   > But the "physical hard disk" (a VHD) is being moved to   
   > a different machine (Hyper V), so I suspect the BIOS   
   > there is using different rules.   
   >   
   > Another factor is that the VHD information (512 bytes   
   > at the end of the file) is not being used by the tool   
   > (freedos under qemu) that formats the disk. I don't   
   > know if the VHD records disk geometry.   
      
   if the V in VHD mean virtual then you only can guess.   
      
   > I noticed that the MBR doesn't seem to record the   
   > disk geometry, so I can't do what I am currently doing   
   > with the VBR. ie I need to get disk geometry from   
   > somewhere else.   
      
   the MBR can only report not record :)   
   there once were reserved disk-geometry entries in MBR,   
   seems they applied to Floppy only yet.   
      
      
   > What options do I have and what are the pros and cons?   
   > You mentioned "identify device". What is that?   
      
   It's called Identify Drive in RBIL look at INT 1325   
   or read RBIL-PORTS: 01F0... command EC(ATA) and A1(ATAPI)   
   are direct ways (w/o needing BIOS) to get all info.   
   I use the latter method for IDE and SATA both HD/CD.   
   __   
   wolfgang   
   (all my figures are HEX, except noted or obvious else)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)