🚀 go-pugleaf

In article <exuptr.476.716143831@exu.ericsson.se> exuptr@exu.ericsson.se (exuptr@exu.ericsson.se) writes:
}In article <BuCBp5.1MF.2@cs.cmu.edu> ralf+@cs.cmu.edu (Ralf Brown) writes:
}>In article <exuptr.458.716059101@exu.ericsson.se> exuptr@exu.ericsson.se (exuptr@exu.ericsson.se) writes:
}>}In article <2aab4eed@ralf> Ralf.Brown@B.GP.CS.CMU.EDU writes:
}>}Now this one makes sense.  Except that BIOS does not limit you to 1024
}>}cylinders, that is DOS.  So theoretically you could have 2048 x 64 x 63.
}
}>Sorry, but that is indeed a BIOS limit, since the BIOS only uses ten bits
}>to specify the cylinder (there are a couple of BIOSes which use twelve
}>bits, but they aren't "standard").  
}
}Find me a 386 with bios that will not support a 1224 cylinder drive.

<reach>.  I'm touching one....

The cylinder number is stored discontiguously in the registers to the BIOS
call; bits 8 and 9 go in the high two bits of the register holding the
sector number.  On those BIOSes which support the nonstandard extension to
twelve bits, bits 10 and 11 go in the high two bits of the register holding
the head number.

}>DOS is simply using the standard BIOS
}>interface--you could always write a device driver that knows about the
}>two nonstandard cylinder bits if you have such a BIOS.
}
}Which almost everyone does, which is why Disk Manager works and can format

No, Disk Mangler installs an extension to the BIOS which uses an extra call
to access cylinders beyond 1023.

----------13EE-------------------------------
INT 13 - SWBIOS - SET 1024 CYLINDER FLAG
        AH = EEh
        DL = drive number (80h, 81h)
Return: CF clear
           AH = 00h
Notes:  the following INT 13 call will interpret the cylinder number as 1024
          less than the desired cylinder
        flag cleared by all INT 13 calls except AH=EEh
        SWBIOS is a TSR by Ontrack Computer Systems; Disk Manager also supports
          these calls
        also supported by HyperDisk v4.01+ and PC-Cache v5.5+, in order to allow
          caching of drives using SWBIOS to access more than 1024 cylinders

}things like the MAXTOR XT-4380.  I haven't seen a BIOS that cannot do this
}since 1987.  Admittedly I stay away from older AT's and PS/2's.
}
}Realistically, what machine today has this limitation?

My machine with a 1989 Phoenix BIOS.  If it isn't a problem, why are all the
big IDE drives sector-translated to 1024 or fewer cylinders (like the one in
my system now)?


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