From: nowhere@nevernet.at   
      
   On 02/04/2022 14:23, muta...@gmail.com wrote:   
   > On Saturday, April 2, 2022 at 12:10:39 PM UTC+11, wolfgang kern wrote:   
   >   
   >> if the V in VHD mean virtual then you only can guess.   
   >   
   > Yes it does.   
   >   
   >> It's called Identify Drive in RBIL look at INT 1325   
   >   
   > Thanks. That is for PS/1-2. I was hoping for something   
   > that would work on the IBM PC XT, which shipped with   
   > a 10 MB hard disk.   
   >   
   > Is there anything wrong with INT 13H AH=08H?   
      
   quote 1308:   
   CF=1: ;error   
     AH = status (07h) (see #00234)   
   CF=0: ;successful   
     AH = 00h   
     AL = 00h on at least some BIOSes   
     BL = drive type (AT/PS2 floppies only)   
     CH = low eight bits of maximum cylinder number   
     CL = maximum sector number (bits 5-0)   
       high two bits of maximum cylinder number (bits 7-6)   
     DH = maximum head number   
     DL = number of drives   
     ES:DI -> drive parameter table (floppies only)   
   ...   
   I think this is a very old obsolete function, but if   
   your BIOS is that old too ...   
      
   look at the weird bit distribution in CX and if DH   
   reports more than 0f heads it's a fake extension.   
   And such fakes may are also be used in the MBR CHS,   
   not necessarily with equal meaning.and then check   
   on INT1321 to see another CHS fake interpretation.   
   with only 4 bits defined for DH there is too much   
   room for various extension methods.   
   Ie: bit 5-7 of DH become bit 8-10 of max cylinder   
        bit 4 of DH become bit 6 of sectors/track.   
   have seen others as well.   
      
   the I/O-port Identify Drive is lesser weird :)   
   and even ATA7 tell that geometry entry is obsolete,   
   it is still there on all HDs I checked on.   
      
   > Note that if I wanted something modern I could just   
   > stick with LBA.   
      
   hard to imagine that 50 year old stuff is still around.   
   __   
   wolfgang   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)