Largest ST-506 (MFM or RLL) type HDD?

Steven Hirsch snhirsch at
Fri Oct 16 06:40:04 CDT 2009

On Thu, 15 Oct 2009, Chuck Guzis wrote:

> On 14 Oct 2009 at 18:10, Steven Hirsch wrote:
>> IIRC, they required the WD2010 controller due to some limitations of
>> the WD10xx series.
> It was a BIOS software limitation, pure and simple.  The "standard"
> INT 13H BIOS interface calls for a 10-sector cylinder number (8 bits
> in CH and 2 "borrowed" bits from the sector number register in CL).
> Some late BIOSes (such as those on the WD1006VSRx) expanded the
> cylinder number by borrowing some bits from the head number in
> register DH.

Hmm.  There was a limitation somewhere that the WD20xx series corrected. 
Number of heads, perhaps?  Or am I confusing things totally?


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